48 Cranial neurosurgery

Aetiology
BRAIN TUMOURS
Brain abscess and empyema
Brain tumours in children
Brainstem death
Classiﬁcation
Clinical features of raised intracranial pressure
Common brain tumours
Craniosynostosis
Cysts
Epilepsy
FUNCTIONAL NEUROSURGERY
HYDROCEPHALUS
INTRACRANIAL INFECTION Meningitis
Intracerebral haemorrhage
Introduction
Investigation of raised intracranial pressure
Learning objectives
Medical management
Movement disorders
Neural tube defects
Neurosurgery in occlusive vascular disease
Obstructive and communicating hydrocephalus
PRACTICAL AND ETHICAL ISSUES Creutzfeldt–Jakob dis
PRACTICAL AND ETHICAL ISSUES Creutzfeldt–Jakob disease
Pain syndromes
Pituitary tumours
Posterior fossa malformations
Presentation
RAISED INTRACRANIAL PRESSURE
Risks of craniotomy
Spina biﬁda occulta
Subdural empyema
Surgical interventional management
Treatment of hydrocephalus
Tuberculosis
VASCULAR NEUROSURGERY Subarachnoid haemorrhage
Vestibular schwannoma

Aetiology

The common primary brain tumours mentioned above mostly occur sporadically . There is no proven risk due to environmen tal factors, except for radiation exposure, but germline genetic syndromes may also predispose ( Table 48.5 ). Theodor Schwann , 1810–1882, Professor of Anatomy , Louvain and Liège, Belgium. German physiologist who established the cellular basis of di ﬀ erentiated tissues including feathers. One of the few clinical syndromes named for the patient rather than the clinician. She died from breast cancer at the age of 20. Frederick Pei Li , 1940–2015, Professor of Medicine, Harvard University Medical School, Boston, MA, USA. Joseph F Fraumeni , b. 1933, Director of Cancer Epidemiology and Genetics, The National Cancer Institute, Bethesda, MD, USA. -

lymphoma Germ cell tumour BRAIN TUMOURS Meningioma Extra-axial Vestibular Neuroepithelial schwannoma Medulloblastoma Neuronal Gliomas tumours Ependymomas and choroid plexus tumours TABLE 48.5 Chromosomal abnormalities associated with brain tumours. Syndrome Gene defect Tumour Neuro /f_i bromatosis Neuro /f_i bromin Astrocytomas; type 1 (chromosome 17) neuro /f_i bromas Neuro /f_i bromatosis Schwannomin Acoustic neuromas type 2 (chromosome 22) (bilateral); meningiomas Cowden’s disease PTEN (chromosome 10) Astrocytomas Multiple Astrocytomas Hereditary non-polyposis colorectal cancer Li–Fraumeni p53 (chromosome 17) Astrocytomas syndrome PTEN , phosphatase and tensin homologue.

Aetiology

BRAIN TUMOURS

The term ‘brain tumour’ applies to more than 100 distinct pathologies detailed in the World Health Organization (WHO) classiﬁcation. Many are malignant, but even histologically benign tumours may carry a grave prognosis when they encroach on key structures that also limit surgical access. The commonest brain tumour is a metastasis. Primary brain

tumours represent 1.5% of all cancers, with an incidence of 19 per 100 /uni00A0 000 person-years. Nevertheless many , especially glial, tumours present commonly in younger age groups and are incurable, so that they are a leading cause of life-years lost to cancer.

Pituitary tumours Craniopharyngioma Tumour-like Colloid malformations cyst Dermoid/epidermoid Pineal tumours Astrocytomas Oligodendrogliomas Figure 48.20 Brain tumour classi /f_i cation. A simpli /f_i ed schema encompassing some of the key brain tumour categories. Highlighted in bold are the pathologies discussed in more detail in this chapter.

BRAIN TUMOURS

Brain abscess and empyema

Abscesses arise when the brain is exposed directly , for example as a result of fracture or infection of an air sinus, or at surgery . They also result from haematogenous spread, typically in asso - ciation with respiratory and dental infections or endocarditis. In 25% of cases, no underlying primary infection is found. The organisms involv ed are normally bacteria, but immuno - compromised hosts in particular are vulnerable to a broad range of pathogens ( Table 48.3 ). Typical presenting features include low-grade fever, confusion, seizures and focal deﬁcit, often with equivocal b lood markers of inﬂammation; blood cultures should be obtained at an early stage. CT scan with contrast is the initial imaging modality of choice. Hypodense oedematous brain r epresenting early cerebritis is visible in the ﬁrst few days ( Figure 48.9 ). The classic appearances of a smooth-walled, well-deﬁned, ring- enhancing mass develop as the abscess matures ( Figure 48.10 ). The distinction between abscess and tumour can be di ﬃ cult and has important management implications since abscesses generally require urgent drainage. Restricted di ﬀ usion evident on di ﬀ usion-weighted MRI sequences is a valuable indicator of infective pathology ( Figure 48.11 ). The mainstay of abscess management is early surgical drainage: mortality for patients treated in this way is about 4%, whereas it is gr eater than 80% in cases of ventriculitis due to rupture of an abscess into the ventricles. Up to 50% of patients with brain abscess will develop seizures at some stage, so that prophylactic anticonvulsants should be considered.

Figure 48.9 Axial computed tomography scan with contrast of a patient with frontal sinusitis presenting with seizures. Early cerebritis is evident in the left frontal region (arrow). Figure 48.11 The right frontal lesion evident on T2-weighted mag- netic resonance imaging (MRI) (main image) exhibits high signal on diffusion-weighted MRI sequences (top right inset) indicative of brain abscess. Figure 48.10 Axial computed tomography scan with contrast in the same patient as in Figure 48.9 2 weeks later. A ring-enhancing, smooth-walled lesion is evident; this is an abscess suitable for image- guided drainage. TABLE 48.3 Common causative organisms. Condition Organisms Sinus/mastoid infection Streptococci; Bacteroides ; enterobacteria; staphylococci; Pseudomonas Haematogenous spread Bacteroides ; streptococci Penetrating trauma Staphylococcus aureus ; Clostridium ; Bacillus ; enterobacteria Food contamination Toxoplasma ; pork tapeworm (neurocysticercosis) Immunocompromise HIV; Toxoplasma (protozoal); Cryptococcus (fungal); JC virus HIV, human immunode /f_i ciency virus; JC, John Cunningham.

Brain abscesses /uni25CF /uni25CF /uni25CF

Presenting features are those of infection and intracranial mass lesion Imaging reveals a ‘ring-enhancing lesion’, with tumour usually the main differential Early diagnosis, usually followed by drainage, is key for good outcome

Brain abscess and empyema

Brain abscesses /uni25CF /uni25CF /uni25CF

Brain abscess and empyema

Brain abscesses /uni25CF /uni25CF /uni25CF

Brain tumours in children

Brain tumours are the most common solid tumours in children but are nonetheless seen only infrequently outside specialist units. They typically present with developmental regression and enlarging head circumference in the youngest, with head - ache, seizure and focal deﬁcits prominent in older children. Posterior fossa tumours are relatively more common in children, in particular: /uni25CF medulloblastoma; /uni25CF ependymoma; /uni25CF pilocytic astrocytoma. Treatment will typically combine surgical resection or biopsy , CSF diversion, chemotherapy and/or radiotherapy .

Brain tumours in children

Brainstem death

This is deﬁned as the irreversible loss of cerebral and brainstem function. Brainstem death is legally equivalent to death, and is a precondition for the harvesting of organs for transplant from heart-beating donors. /uni25CF identiﬁcation of the cause of irreversible coma; /uni25CF exclusion of reversible causes of coma; /uni25CF clinical demonstration of the absence of brainstem func tion. In the UK, this entails testing twice, by two clinicians, to demonstrate the absence of: /uni25CF response to pain; /uni25CF respiratory drive (apnoea despite a P CO >6.7 /uni00A0 kPa); 2 /uni25CF pupillary light reﬂex; /uni25CF corneal reﬂex; /uni25CF vestibulo-ocular reﬂex; /uni25CF oculocephalic reﬂex; /uni25CF gag reﬂex. Greenberg MS. Handbook of neurosurgery, 9th edn. New Y ork, NY: Thieme, 2019. Patton J. Neurological di ﬀ erential diagnosis, 2nd edn. New Y ork, NY: - Springer, 1998. Samandouras G. The neurosurgeon’s handbook. Oxford: Oxford Publish - ing, 2010. Brainstem death
This is deﬁned as the irreversible loss of cerebral and brainstem function. Brainstem death is legally equivalent to death, and is a precondition for the harvesting of organs for transplant from heart-beating donors. /uni25CF identiﬁcation of the cause of irreversible coma; /uni25CF exclusion of reversible causes of coma; /uni25CF clinical demonstration of the absence of brainstem func tion. In the UK, this entails testing twice, by two clinicians, to demonstrate the absence of: /uni25CF response to pain; /uni25CF respiratory drive (apnoea despite a P CO >6.7 /uni00A0 kPa); 2 /uni25CF pupillary light reﬂex; /uni25CF corneal reﬂex; /uni25CF vestibulo-ocular reﬂex; /uni25CF oculocephalic reﬂex; /uni25CF gag reﬂex. Greenberg MS. Handbook of neurosurgery, 9th edn. New Y ork, NY: Thieme, 2019. Patton J. Neurological di ﬀ erential diagnosis, 2nd edn. New Y ork, NY: - Springer, 1998. Samandouras G. The neurosurgeon’s handbook. Oxford: Oxford Publish - ing, 2010. Brainstem death
This is deﬁned as the irreversible loss of cerebral and brainstem function. Brainstem death is legally equivalent to death, and is a precondition for the harvesting of organs for transplant from heart-beating donors. /uni25CF identiﬁcation of the cause of irreversible coma; /uni25CF exclusion of reversible causes of coma; /uni25CF clinical demonstration of the absence of brainstem func tion. In the UK, this entails testing twice, by two clinicians, to demonstrate the absence of: /uni25CF response to pain; /uni25CF respiratory drive (apnoea despite a P CO >6.7 /uni00A0 kPa); 2 /uni25CF pupillary light reﬂex; /uni25CF corneal reﬂex; /uni25CF vestibulo-ocular reﬂex; /uni25CF oculocephalic reﬂex; /uni25CF gag reﬂex. Greenberg MS. Handbook of neurosurgery, 9th edn. New Y ork, NY: Thieme, 2019. Patton J. Neurological di ﬀ erential diagnosis, 2nd edn. New Y ork, NY: - Springer, 1998. Samandouras G. The neurosurgeon’s handbook. Oxford: Oxford Publish - ing, 2010.

Classiﬁcation

WHO classiﬁes primary brain tumours on the basis of cell of origin and histological grade ( Figure 48.20 ), with the 2016 edition including a number of additional molecular classiﬁca tions assigned in parallel to constitute an ‘integrated’ diagnosis. Common adult primary brain tumours include gliomas, meningiomas (15–20% of total), pituitary adenomas (10–15% of total) and vestibular schwannomas. Grade I is applied to ‘benign’ lesions, while grade IV implies high-grade malignancy . Classiﬁcation

Clinical features of raised intracranial pressure

Symptoms of raised ICP include a ‘high-pressure headache’ that is worse on coughing or bending forward. By contrast, low-pressure headaches, typically associated with excessive Henri Parinaud , 1844–1905, French ophthalmologist and pioneer in neuro-ophthalmology . cerebrospinal ﬂuid (CSF) drainage, are worse on standing. High-pressure headaches may be accompanied by nausea and vomiting, blurred vision and double vision: cranial nerve compression can result in eye movement and pupil abnormal - ities. Fundoscopy can detect papilloedema ( Figure 48.1 ), but this takes time to develop so may be absent in the acute phase. Before closure of the skull sutures in infancy , raised ICP presents di ﬀ erently with an increase in head circumference, prominent scalp v eins and a tense bulging fontanelle. In infants and older children, raised CSF pressure results in dorsal mid - brain compression with a loss of upgaze known as sunsetting, a feature of Parinaud’s syndrome ( Figure 48.2 ). Raised ICP requires urgent evaluation and management: delay risks progression to cerebral herniation resulting in cardio - vascular instability , neurological deﬁcit and death. Vision ma y also deteriorate rapidly and irreversibly . Where there are pupil changes or a deterioration in conscious level, anaesthetic and

Figure 48.1 Papilloedema. The optic disc is swollen with blurred margins. To be aware of common developmental and other • pathologies encountered in paediatric neurosurgical practice and emergency paediatric care To understand the indications and approaches available • for the management of epilepsy, pain syndromes and movement disorders To note key practical and ethical issues relating to • consent and risks, Creutzfeldt–Jakob precautions and the diagnosis of brainstem death Figure 48.2 Parinaud’s syndrome with sunsetting.

administer hypertonic saline or mannitol and arrange urgent computed tomography (CT) imaging. Clinical features of raised intracranial pressure

administer hypertonic saline or mannitol and arrange urgent computed tomography (CT) imaging.

Common brain tumours

Cerebral metastases Cerebral metastases ( Figure 48.21 ) are the most common intracranial tumours and are diagnosed in 25% of patients with cancer, a proportion that is increasing with extended survival associated with more e ﬀ ective treatment of primary cancers. The tumours of origin and their contribution to the burden of cerebral metastases are detailed in Table 48.7 . Traditionally Robert Foster Kennedy , 1884–1952, British Neurologist, awarded the Chevalier de la Légion d’honneur in recognition of his service in French front-line ﬁeld hospitals in the First World War. Josef Gerstmann , 1887–1969, Austrian neurologist who ﬂed to America in 1938 to escape the Nazis. - ).

certain tumours. Tumour location Expected de /f_i cit Pituitary (e.g. pituitary Bitemporal hemianopia; gaze adenoma) palsies Cerebellopontine angle (e.g. Hearing loss; balance vestibular schwannoma) disturbance; tinnitus Anterior skull base (e.g. Anosmia; ipsilateral optic olfactory groove meningioma) atrophy; contralateral papilloedema (Foster Kennedy syndrome) Occipital (e.g. glioma, Homonymous hemianopia with metastasis) central sparing Parietal (dominant hemisphere) Acalculia; agraphia; left–right disorientation; /f_i nger agnosia (Gerstmann’s syndrome) Parietal (e.g. glioma) Sensory inattention; dressing apraxia; astereognosis Temporal (e.g. glioma) Memory disturbance; contralateral superior quadrantanopia; dysphasia (dominant hemisphere) Frontal (e.g. glioma) Personality change; gait disturbance; urinary incontinence Brainstem (e.g. brainstem Multiple cranial nerve de /f_i cits; glioma) long tract signs; nystagmus Posterior fossa (e.g. Ataxia; hydrocephalus medulloblastoma) Figure 48.21 T1-weighted magnetic resonance imaging with contrast. Two right occipital lung metastases are demonstrated. They are well demarcated and enhance with gadolinium contrast.

able for surgery . In patients with good functional status and well-controlled systemic disease, craniotomy for resection of a single focus, and in selected cases multiple lesions, may confer symptomatic and survival beneﬁts. New molecular therapies can control systemic disease in man y cancers; in these cases craniotomy and resection of one or more lesions responsible for the mass e ﬀ ect or hydrocephalus with medical treatment of the remaining lesions may be well warranted. Occasionally diagnostic biopsy may be warranted where the primary is unknown. Glioma These are intrinsic tumours with glial histology , with subtypes including astrocytomas, oligodendrogliomas, ependymomas and mixed tumours. This is a tissue diagnosis, but imaging often predicts both a glial origin and the grade of tumour ( Figure 48.22 ). Low-grade glioma (WHO grade II) has a peak incidence in the fourth decade of life, and commonly presents with seizures initially . High-grade gliomas include anaplastic astrocytoma (WHO grade III) and glioblastoma (WHO grade IV), the commonest glial tumour ( Figure 48.23 de novo with the peak incidence in the ﬁfth and typically present sixth decades of life, respectively , or arise by transformation of low-grade tumours. MRI of the head with and without contrast is the preferred modality , generally combined with CT of the chest, abdomen and pelvis to exclude an extracranial primary , since metastasis is usually the main di ﬀ erential diagnosis. Di ﬀ usion-weighted MRI sequences are valuable in excluding another key di ﬀ er - ential diagnosis – brain abscess , which is associated with prom - inent restricted di ﬀ usion in these images. Initial management of these tumours should generally include high-dose steroids to alleviate any mass e ﬀ ect. Anti- epileptics are administered when seizures are a presenting feature or are anticipated in view of the temporal loca tion. Sur - ). They gical resection is usually the primary treatment, with the aim of reducing disease burden and obtaining tissue for diagnosis. When tumours encroach on the eloquent cortex, especially the speech areas of the dominant hemisphere which are not consistently ana tomically localised, awake craniotomy allows for mapping of speech function. Except for grade I pilocytic astrocytomas typically found in children, gliomas are notable for di ﬀ use inﬁltration into the surrounding brain, so that recur - rence after even macroscopically complete resection is the rule. The classiﬁcation of gliomas has been signiﬁcantly updated with the recent addition of integrated molecular diagnostic categories to the WHO 2016 classiﬁcation ( Figure 48.24 ). Gliomas with low-grade histolog y often carry characteristic mutations; for example, point mutations in isocitrate dehydro - genase ( IDH ) enzymes and 1p/19q chromosomal co-deletion, the latter speciﬁc to oligodendrogliomas. Glioblastomas are WHO grade IV tumours and include IDH wild-type ‘primary’ glioblastoma and occasional IDH mutant ‘secondary’ glioblas - tomas. These are thought to arise from transformation of pre - viously diagnosed, or clinically silent, low-grade gliomas. IDH wild-type status is a strong predictor of aggressive malignant behaviour, even in the absence of high-grade histological fea - tures. Active treatment consists of maximal surgical resection, typically with the assistance of intraoperative neuronavigation systems to accurately localise the tumour.

TABLE 48.7 Tissue of origin for brain metastases (approximate). Origin Percentage Lung 40 Breast 15 Melanoma 10 Renal/genitourinary 10 Other/unknown 25 Figure 48.22 Computed tomography with contrast demonstrates a heterogeneous right frontoparietal lesion with mass effect and midline shift, almost certainly a glioblastoma multiforme. A magnetic reso nance imaging scan with and without contrast will aid evaluation. Figure 48.23 Pathological specimen of glioblastoma multiforme.

Patients can also be dosed with 5-aminolevulinic acid (5-ALA) preoperatively . Protoporphyrin IX, a ﬂuorescent metabolite of this drug, accumulates selectively in glioma cells, causing them to glow pink under ultraviolet light, so providing a real-time assessment of tumour inﬁltration at the resection boundaries. First-line adjuvant treatment in malignant glioma includes high-dose focused radiation therapy and alkylating chemother apy with oral temozolomide. Median survival for glioblastoma remains just over 12 months. Meningioma Meningiomas are usually benign lesions, although anaplastic variants do occur. They arise from the meninges and typi cally present as a result of the mass e ﬀ ect from the tumour, compounded by vasogenic oedema in the adjacent brain and obstructive hydrocephalus where CSF drainage is impair Imaging will demonstrate a contrast-enhancing mass distinct from the brain with a dural base ( Figure 48.25 ). These are generally slow-growing lesions: smaller lesions, perhaps detected incidentally in an elderly patient, may well warrant a ‘watch-and-wait’ approach. If the lesion is large or positioned so as to impinge on key structures, the patient may requir e steroids and early surgery . The degree of resection pre dicts recurrence, with rates of 10% at 10 years for total excision with a clear dural margin and 30% at 10 years for subtotal excision. Lesions that are di ﬃ cult to approach surgically may be managed with radiotherapy or stereotactic radiosurgery Martin Heinrich Rathke , 1793–1860, German anatomist. α Summary box 48.10 Common supratentorial brain tumours /uni25CF /uni25CF - /uni25CF /uni25CF - /uni25CF ed.

IDH status IDH mutant 1p/19q and a ATRX loss 1p/19q other genetic a TP53 mutation co-deletion parameters Diffuse astrocytoma, IDH mutant Oligodendroglioma, IDH mutant and 1p/19q co-deleted After exclusion of other entities: Diffuse astrocytoma, Oligodendroglioma, NOS Figure 48.24 World Health Organization 2016 classi /f_i cation of gliomas. ATRX, a IDH, isocitrate dehydrogenase; NOS, not otherwise speci /f_i ed. A, Reifenberger G et al . The 2016 World Health Organization classi /f_i cation of tumors of the central nervous system: a summary. 2016; 131 (6): 803–20, with permission from Springer.) IDH wild type IDH mutant IDH wild type Glioblastoma, IDH mutant Glioblastoma, IDH wild type Genetic testing not done or inconclusive Diffuse astrocytoma, NOS Oligodendroglioma, NOS IDH wild type Oligoastrocytoma, NOS Glioblastoma, NOS -thalassaemia/mental retardation syndrome X-linked; Characteristic but not required for diagnosis. (Reproduced from Louis DN, Perry Acta Neuropathol Metastases and gliomas are common tumours arising within brain substance, appearing as ‘ring-enhancing’ lesions on contrast CT. Surgery is usually life-extending rather than curative Meningiomas arise from the meninges around the brain and typically enhance uniformly on contrast CT. Most are benign and amenable to curative resection MRI is usually the best modality for evaluating brain tumours. Diffusion-weighted sequences help to exclude abscess when glioma or metastasis is suspected Metastasis is the main differential diagnosis, and CT of the body is useful in identifying extracranial primary tumours Steroids, along with proton pump inhibitor treatment for gastric protection, are administered to control swelling and the mass effect in the short term

Common brain tumours

TABLE 48.7 Tissue of origin for brain metastases (approximate). Origin Percentage Lung 40 Breast 15 Melanoma 10 Renal/genitourinary 10 Other/unknown 25 Figure 48.22 Computed tomography with contrast demonstrates a heterogeneous right frontoparietal lesion with mass effect and midline shift, almost certainly a glioblastoma multiforme. A magnetic reso nance imaging scan with and without contrast will aid evaluation. Figure 48.23 Pathological specimen of glioblastoma multiforme.

Common brain tumours

TABLE 48.7 Tissue of origin for brain metastases (approximate). Origin Percentage Lung 40 Breast 15 Melanoma 10 Renal/genitourinary 10 Other/unknown 25 Figure 48.22 Computed tomography with contrast demonstrates a heterogeneous right frontoparietal lesion with mass effect and midline shift, almost certainly a glioblastoma multiforme. A magnetic reso nance imaging scan with and without contrast will aid evaluation. Figure 48.23 Pathological specimen of glioblastoma multiforme.

Craniosynostosis

Normal fusion of the coronal, lambdoidal, squamosal and sagittal sutures occurs between 6 and 12 months of age; others such as the frontal suture fuse later. Craniosynostosis is the premature fusion of one (simple craniosynostosis) or more (complex craniosynostosis) cranial sutures, preventing growth - perpendicular to the suture. This results in a range of skull deformities ( Table 48.8 and Figures 48.29 and 48.30 ) and hydrocephalus. Syndromic craniosynostosis, often associated - with abnormalities of the ﬁbroblast growth factor receptor genes, is accompanied by developmental delay and other abnormalities. The surgical treatment aims to correct defor - mity and prevent development of raised ICP . -

TABLE 48.8 Types of craniosynostosis. Type Suture involved Clinical features Scaphocephaly Sagittal suture Narrow boat-shaped head Brachycephaly Coronal suture Shortened/broad forehead Microcephaly All sutures involved Small head Plagiocephaly Unilateral coronal/ Asymmetric skull lambdoid suture Trigonocephaly Metopic suture Pointed narrow forehead

Craniosynostosis

Cysts

These benign ﬂuid-ﬁlled intracranial lesions typically present incidentally or with mass e ﬀ ect or hydrocephalus. Treatment of symptomatic or enlarging lesions is usually surgical, involv - ing excision, endoscopic fenestration into a cistern or ventricle or shunting for hydrocephalus. Cyst types include: - /uni25CF arachnoid cyst: typically middle fossa, CSF enclosed in an envelope of arachnoid mater; /uni25CF colloid cyst: occur in the roof of the third ventricle, be - will lieved to represent embryonic endoderm remnants; /uni25CF dermoid and epidermoid cysts: epithelium-lined structures arising from displaced ectodermal remnants, typically in the posterior fossa (midline) and cerebellopontine angle, respectively; /uni25CF porencephalic cysts: brain cavities lined with gliotic white matter, containing CSF in communication with the ventri - cles or subarachnoid space. Cysts

Epilepsy

Up to 10% of the population will su ﬀ er a seizure at some point in their lives, and epilepsy , a syndrome of recurrent unpro voked seizures, represents the most common neurological disorder. About 20–30% of patients fail to achieve adequate seizure control with drugs, and many of these focal epilepsies may beneﬁt fr om surgery . Where a primary lesion such as a tumour, A VM or cavernoma is present, lesionectomy alone may be appropriate. Over time, however , repeated seizures can trigger hippocampal atrophy , which can then present a second - seizure focus. This dual pathology is clinically important because seizure control may require removal of the atrophic hippocampus as well as the primary pathology .

Figure 48.29 (a–c) Characteristic appearance of scaphocephaly due to sagittal suture synostosis. Figure 48.30 Axial computed tomography scan showing severe trigo

nocephaly due to premature fusion of the metopic suture.

MRI is a mainstay , demonstrating, for example, reduced hippocampal volume and distorted architecture in mesial temporal sclerosis. Nuclear medicine modalities, including single-photon emission CT (SPECT) and positron emission tomography (PET), are sometimes used to demonstrate ictal and interictal metabolic abnormalities. Electroencephalography (EEG) entails recording from an array of scalp electrodes and comparison between ictal and interictal recordings. This is especially helpful in lateralising the focus of complex partial seizures in temporal lobe epilepsy and is combined with video monitoring of the seizur videotelemetry suite. A more detailed localisation may be achieved invasively by the preoperative placement of subdural or depth electrodes, preoperatively or by intraoperative electrocorticography (ECoG). Neuropsychological evaluation is used to evaluate the patient’s preoperative function, looking for concordant focal impairments and, using the Wada test ( Table 48.9 ), assessing the risk of postoperative language and memory deﬁcits in tem poral lobe epilepsy surgery . /uni25CF /uni25CF Surgical management The seizure focus may be resected, generally where it is in non-eloquent brain, or otherwise a disconnection can be performed. Awake craniotomy , allowing mapping particularly of speech centres, is increasingly employed. Mesial temporal epilepsy is commonly medically refractory and can be addressed surgically by amygdalohippocampec tomy or resection of the temporal lobe including the mesial structures. With careful patient selection, cure rates of up to 70% or g reater can be achieved. Functional, or rarely anatomical, hemispherectom ( Figure 48.31 ) may be performed for speciﬁc epilepsy syndromes associated with hemiplegia, such as infantile hemiplegia syndrome. This is usually considered in the early years of life when plasticity and potential for functional recovery is greatest. Disconnection procedures include corpus callosotomy , which is used for patients su ﬀ ering drop attacks, and subpial transections to isolate a seizure focus in eloquent brain from the surrounding cortex. Vagal nerve stim ulators can be implanted in severe drug- refractory epilepsy , with electrodes applied to the vagus nerve in the carotid sheath in the neck. This option can achieve Juhn Atsushi Wada , b. 1924, Japanese–Canadian neurologist known for research into epilepsy and human brain asymmetry , including his description of the Wada test for cerebral hemispheric dominance of language function. James Parkinson , 1755–1824, general practitioner of Shoreditch, London, UK, published e in a - signiﬁcant reductions in seizure frequency , especially in children, although the mechanism is not clear.

TABLE 48.9 Wada test. Sodium amytal is injected into each internal carotid artery in turn, with simultaneous speech and memory testing to localise function The aim is to con /f_i rm language laterality, and hence that resection on the side of the lesion will not signi /f_i cantly impair verbal memory functions Figure 48.31 Coronal T2-weighted magnetic resonance image follow

ing anatomical hemispherectomy.

Epilepsy

Figure 48.29 (a–c) Characteristic appearance of scaphocephaly due to sagittal suture synostosis. Figure 48.30 Axial computed tomography scan showing severe trigo

nocephaly due to premature fusion of the metopic suture.

TABLE 48.9 Wada test. Sodium amytal is injected into each internal carotid artery in turn, with simultaneous speech and memory testing to localise function The aim is to con /f_i rm language laterality, and hence that resection on the side of the lesion will not signi /f_i cantly impair verbal memory functions Figure 48.31 Coronal T2-weighted magnetic resonance image follow

ing anatomical hemispherectomy.

Epilepsy

Figure 48.29 (a–c) Characteristic appearance of scaphocephaly due to sagittal suture synostosis. Figure 48.30 Axial computed tomography scan showing severe trigo

nocephaly due to premature fusion of the metopic suture.

TABLE 48.9 Wada test. Sodium amytal is injected into each internal carotid artery in turn, with simultaneous speech and memory testing to localise function The aim is to con /f_i rm language laterality, and hence that resection on the side of the lesion will not signi /f_i cantly impair verbal memory functions Figure 48.31 Coronal T2-weighted magnetic resonance image follow

ing anatomical hemispherectomy.

FUNCTIONAL NEUROSURGERY

Functional neurosurgery aims to relieve epilepsy , movement disorders or pain by ablation or stimulation of brain tissue and nerves. Summary box 48.12 Paediatric neurosurgery /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF

(c) A large variety of mostly neuroectodermal brain tumours represent the most common solid organ tumours in children Children manifest a range of developmental pathologies requiring neurosurgical management, including: Cysts Neural tube defects Posterior fossa abnormalities Craniosynostosis Generic features of intracranial pathology include developmental delay, seizures, macrocephaly and hydrocephalus

FUNCTIONAL NEUROSURGERY

HYDROCEPHALUS

The total volume of CSF is normally about 150 /uni00A0 mL. Produc tion from the walls of the ventricles and the choroid plexus is about 20 /uni00A0 mL/h. Hydrocephalus refers to an increase in CSF volume with ventricular enlargement, often presenting symptoms of raised ICP . Alexander Monro , 1733–1817, Professor of Anatomy , The University of Edinburgh, Edinburgh, UK, a post also held by his father, Alexander Monro (primus), and son, Alexander Monro (tertius). Francois Magendie , 1783–1855, Physician and Professor of Pathology and Physiology , Paris, France. Also described the Magendie sign, a downward and inward rotation of the eye due to a cerebellar lesion. Hubert von Luschka , 1820–1875, anatomist, University of Tübingen, Tübingen, Germany . CSF ﬂows from the lateral ventricles through the foramen of Monro to the third ventricle, then down the cerebral aqueduct to the fourth ventricle, where it exits to the subarachnoid space via the midline foramen of Magendie and the lateral foramina of Luschka ( Figure 48.4 ). CSF is reabsorbed into the arach - noid villi along the superior sagittal sinus. - HYDROCEPHALUS

INTRACRANIAL INFECTION Meningitis

Meningitis describes inﬂammation of the meninges of the brain and spinal cord, most commonly and most seriously due to bacterial infection. The clinical features of meningeal irritation or meningism are fever, headache, neck sti ﬀ ness and photophobia. Community-acquired bacterial meningitis can progress rapidly without antibiotic treatment to subpial encephalopathy , venous thrombosis, cerebral oedema and death. Meningitis as a complication of head injury or surgery typically follows a more insidious course, but nonetheless remains a feared complication requiring prompt intervention. Hans Christian Joachim Gram , 1853–1938, Professor of Pharmacology (1891–1900) and of Medicine (1900–1923), Copenhagen, Denmark, described this method of staining bacteria in 1884. /uni25CF /uni25CF /uni25CF Typical organisms are Staphylococcus aureus , Enterobacteria - ceae, Pseudomonas and pneumococci. Meningitis after head injury is common, a ﬀ ecting 25% of patients with base of skull fracture and CSF leak. Repair - of the CSF leak may be required, and empirical antibiotics ( Table 48.2 ) should have activity against commensal nasal org anisms, including Gram-positive cocci and Gram-negative bacilli in the presence of symptoms/signs of clinical menin - gitis. Summary box 48.4 - Meningitis /uni25CF /uni25CF /uni25CF /uni25CF

antibiotic therapy. Treatment should be initiated as soon as feasible, allowing for sampling of collections or CSF /f_i rst if the patient’s clinical condition allows High-dose empirical intravenous antibiotics are administered according to local protocol, broad spectrum initially and then according to sensitivities of the organisms responsible once identi /f_i ed Extended treatment over 6 weeks or more is typically required, but a switch to oral therapy may be appropriate after an interval and in consultation with the microbiology team A feared complication of neurosurgery and of head injury CT head allows exclusion of raised ICP prior to lumbar puncture CSF should be sent for microscopy and culture, and for assay of protein and glucose levels Treatment, pending identi /f_i cation of an organism, is with broad -spectrum antibiotics, including anaerobic cover

INTRACRANIAL INFECTION Meningitis

Intracerebral haemorrhage

Intracerebral haemorrhage (ICH) typically presents with sudden focal deﬁcit and a reduced conscious level. Following initial resuscitation, these patients will require CT scan to establish the diagnosis and the size and position of the bleed ( Figure 48.17 ). They require reversal of anticoagulation, ongoing hourly neuro-observations and blood pressure monitoring. High blood pressure may be longstanding and associated with adaptations to autoregulation, so attempts at lowering it acutely with intravenous antihypertensives should Christian Johann Doppler , 1803–1853, Professor of Experimental Physics, Vienna, Austria, enunciated the ‘Doppler principle’ in 1842. pressure >130 /uni00A0 mmHg). - Spontaneous ICH accounts for 10–15% of strokes and has a mortality of 40% at 1 year. The majority occur in the context of hypertension or amyloid angiopathy , or as a complica tion of ischaemic stroke. Coagula tion disorders, especially patients being treated with warfarin, are a major risk factor. In younger patients and where the pattern of bleeding is atypical, dedi - cated imaging to rule out an underlying vascular anomaly or tumour is required. For example it is critically important to identify ICH due to aneurysm rupture or A VM befor e consid - ering surgical intervention. Craniotomy and evacuation may be used to alleviate raised ICP . Importantly this surgery may be life-saving by reliev - ing raised ICP but cannot reverse deﬁcits resulting from the haematoma dir ectly . Surgical evacuation would typically be a good option for younger, ﬁtter patients with signs of raised ICP and haematomas close to the cortical surface or in the posterior fossa. Summary box 48.8 Intracerebral haemorrhage /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF -

These account for 10–15% of strokes Presentation is with headache, focal de /f_i cits and signs of raised ICP High blood pressure may be chronic so should only be reduced with care Anticoagulants should be reversed In /f_i t patients, clot evacuation is an option to relieve raised ICP but not reverse de /f_i cits Further imaging may be required to exclude an underlying vascular or neoplastic lesion Figure 48.17 Large acute intracerebral haemorrhages in the right frontal and parietal lobes are evident, with surrounding oedema and midline shift.

Vascular malformations are usually congenital in origin, with certain key exceptions discussed below . They may present with headaches, pulsatile tinnitus, seizures or focal deﬁcit, or else acutely with rupture and haemorrhage. A VMs are responsible for a small proportion of SAHs and ICHs. V essels and calciﬁcation may be apparent on CT or MRI and the lesion is conﬁrmed on angiography ( Figure 48.18 Depending on the size, location and venous drainage pat terns, surgery or radiosurgery are usually preferred treatment options. In some cases endovascular embolisation with tissue glue may have a role, and for many A VMs there is no treatment with a satisfactory risk–beneﬁt ratio. V ein of Galen malformations are A VMs feeding into an embryological venous remnant dorsal to the brainstem, pre senting in childhood. High-ﬂow malformations may cause car diac failure. They ma y be treated by embolisation. Dural arteriovenous ﬁstulae (DA VFs) are shunts between dural arteries and veins or sinuses. They are proposed to arise as a result of vessel remodelling in response to dural sinus thrombosis and subsequent r ecanalisation. They may present with subarachnoid, intracerebral or subdural bleeding, or with headache and pulsatile tinnitus. A carotid cavernous ﬁstula is a spontaneous or traumatic DA VF between the internal carotid artery and surrounding cavernous sinus, typically producing eye pain, ocular muscle palsies and exophthalmos. Angiogra phy is diagnostic. Cavernomas ( Figure 48.19 ) are discrete venous anomalies within brain tissue, visible on MRI but not angiography , that can bleed r epeatedly , causing progressive deﬁcit. They can be removed surgically if required. Related lesions, usually clinically silent, include develop mental venous anomalies and capillary telangiectasia. Galen , 130–200, Roman physician, commenced practice as Surgeon to the Gladiators at Pergamum (now Bergama in Turkey) and later became personal physician to the Emperor Marcus Aurelius and to two of his successors. He was a proliﬁc writer on many subjects, among them anatomy , medicine, pathology and philosophy . His work a ﬀ ected medical thinking for 15 centuries after his death. (Gladiator is Latin for ‘swordsman’.) ). - - -

Figure 48.18 An arteriovenous malformation supplied by the anterior cerebral, middle cerebral and middle meningeal arteries is demon strated at the 4 o’clock position in this angiogram. Figure 48.19 A brainstem cavernoma (arrow).

Intracerebral haemorrhage

Introduction

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Investigation of raised intracranial pressure

CT is a ﬁrst-line investigation to identify causes of raised ICP , including mass lesions, bleeds, cerebral oedema and hydro cephalus, and to guide treatment. Outside the emergency setting many pathologies, as well as the anatomy relating to potential treatments such as third ventriculostomy , may be better visualised on magnetic resonance imaging (MRI). T gold standard for quantifying ICP and monitoring in real time is by transducing CSF pressure through an external ventric ular drain or insertion of a pressure monitor into the brain substance ( Figure 48.3 ). Summary box 48.1 Raised ICP /uni25CF /uni25CF /uni25CF /uni25CF

P1 P2 P3 Normal brain P2 P3 P1 Pressure Injured brain Time Figure 48.3 The intracranial pressure waveform. The P1 percussion wave corresponds to arterial pulsation. Reduced brain compliance in the setting of traumatic brain injury among others is associated with a prominent P2 tidal wave. The P3 dicrotic wave represents venous pulsation. Acutely raised ICP is a neurosurgical emergency. Clinical features include: Headache Nausea and vomiting Diplopia and blurred vision Drowsiness then coma

Investigation of raised intracranial pressure

Learning objectives

To understand the physiology of raised intracranial • pressure, cerebrospinal /f_l uid circulation and intracranial blood /f_l ow To recognise central nervous system infection, and • understand the acute management To be familiar with causes of spontaneous intracranial • haemorrhage and the principles of management of subarachnoid haemorrhage To recognise common intracranial tumours, their • presentation, investigation and treatment Learning objectives

Medical management

Patients should be placed on bed rest with hourly neuro - observations. They require strict input–output monitoring and intravenous ﬂuid replacement with normal saline initially . Oral - nimodipine at a dose of 60 /uni00A0 mg every 4 hours is administered to reduce the incidence of vasospasm and dela yed ischaemic neurological deﬁcit. Analgesics, laxatives, antiemetics, gastric protection and compression stockings are also likely to be necessary . After resuscitation, the priorities in SAH are to: 1 prevent rebleeding by identifying and controlling any underlying lesion; 2 recognise and manage: /uni25CF neurological complications, especially vasospasm, delayed ischaemic neurological deﬁcit and hydro - cephalus; ance, severe hypertension, cardiac infarct and arrhyth mia, and neurogenic pulmonary oedema. These goals are best served by early transfer of the patient to a neurosurgical centre. In elderly patients with a poor WFNS grade, a decision to o ﬀ er only supportive management may be appropriate. Neurological deterioration should prompt a repeat scan to exclude evidence of rebleeding and of hydrocephalus. T his is typically the communicating type, which is a common complication of haemorrhage. Where these complications are not demonstrated, deterioration may reﬂect delayed ischaemic neurological deﬁcit (DNID), which commonly develops 3–10 days after aneurysmal haemorrhage and can progress rapidly to infarction. The process is attributed to cerebral vasospasm in response to, and correlating with, the blood load. This process can be visualised angiographically or by perfusion CT , and the velocity of blood ﬂow in the cerebral vasculature measured using transcranial Doppler ultrasound can also provide an indirect assessment of the degree of stenosis. Outcomes are optimised by the prophylactic administration of nimodipine and maintenance of ﬂuid volume, typically with 2.5–3 /uni00A0 L/day of normal saline. In established vasospasm, the goal is to maintain cerebral perfusion by administration of ﬂuid and inotropes. Hyponatraemia is a frequent complication of SAH, attributed to cerebral salt wasting in the context of ﬂuid depletion and to the syndrome of inappropria te antidiuretic hormone secretion otherwise. This is associated with a higher incidence of DNID; practical management, irrespective of the underlying pathology , is based on sodium replacement with hypertonic infusions if necessary . Fluid restriction is not appro priate in these patients since this risks further compromising perfusion. Summary box 48.7 Subarachnoid haemorrhage /uni25CF /uni25CF /uni25CF

Most result from rupture of an aneurysm in the circle of Willis Plain CT and lumbar puncture are /f_i rst-line investigations Even ‘good grade’ patients treated promptly have a signi /f_i cant morbidity owing to vasospasm, cardiac arrhythmias, neurogenic pulmonary oedema, etc.

Medical management

Movement disorders

Prior to the development of levodopa drug therapy , surgical ablation of the subthalamic nucleus (STN) or globus pallidus interna (GPi) was a mainstay of management for Parkinson’s disease. Inhibition of the action of these centres remains a - valuable tool later in the course of the disease as the therapeu - tic window using levodopa narrows, but this is now achieved using deep brain stimulation with electrodes. This o ﬀ ers the advantage of an adjustable and reversible e ﬀ ect and can be y performed bila terally where equivalent lesioning surgery would probably result in deﬁcits. Deep brain stimulation is also an option for other move - ment disorders where less invasive approaches are ine ﬀ ective. These include dystonias, which may be amenable to bilateral GPi stimulation, and essential tremor, where the ventralis inter - mediate n ucleus (Vim) of the thalamus is a preferred target. Movement disorders

Neural tube defects

Failure of closure of the neural tube is associated with folate deﬁciency , family history and some anticonvulsants. Prenatal screening, using serum α -fetoprotein levels and ultrasound, and diagnostic testing, using amniocentesis, are possible. The spectrum of conditions associated with failed closure of the posterior neuropore includes the conditions described below . Neural tube defects

Neurosurgery in occlusive vascular disease

In a subgroup of patients with completed ischaemic strokes, generally in the middle cerebral artery territory or posterior fossa, there is a role for decompressive craniectomy in the 2–3 days after ictus to manage brain swelling and raised ICP associated with the infarct. There is class 1 evidence for the role of carotid endarterec - - tomy in reducing the risk of stroke in patients with symptom - atic carotid stenosis, and a debatable role for the procedure in patients with no previous transient ischaemic episodes. Moyamoya disease entails the progressive obliteration of otid arteries, thought to represent an one or both internal car autoimmune process. The development of external carotid tion collaterals produces the angiographic ‘pu ﬀ of circula smoke’ appearance from which the term derives. It presents in youth or early middle age with ischaemia or haemorrhage. Untreated, the majority of patients su ﬀ er major deﬁcit or die within 2 years. Ischaemia may be addressed by a variety of bypass techniques, for example by anastomosing the super - ﬁcial temporal artery (arising from the external carotid) to the middle cerebral artery . Neurosurgery in occlusive vascular disease
In a subgroup of patients with completed ischaemic strokes, generally in the middle cerebral artery territory or posterior fossa, there is a role for decompressive craniectomy in the 2–3 days after ictus to manage brain swelling and raised ICP associated with the infarct. There is class 1 evidence for the role of carotid endarterec - - tomy in reducing the risk of stroke in patients with symptom - atic carotid stenosis, and a debatable role for the procedure in patients with no previous transient ischaemic episodes. Moyamoya disease entails the progressive obliteration of otid arteries, thought to represent an one or both internal car autoimmune process. The development of external carotid tion collaterals produces the angiographic ‘pu ﬀ of circula smoke’ appearance from which the term derives. It presents in youth or early middle age with ischaemia or haemorrhage. Untreated, the majority of patients su ﬀ er major deﬁcit or die within 2 years. Ischaemia may be addressed by a variety of bypass techniques, for example by anastomosing the super - ﬁcial temporal artery (arising from the external carotid) to the middle cerebral artery . Neurosurgery in occlusive vascular disease
In a subgroup of patients with completed ischaemic strokes, generally in the middle cerebral artery territory or posterior fossa, there is a role for decompressive craniectomy in the 2–3 days after ictus to manage brain swelling and raised ICP associated with the infarct. There is class 1 evidence for the role of carotid endarterec - - tomy in reducing the risk of stroke in patients with symptom - atic carotid stenosis, and a debatable role for the procedure in patients with no previous transient ischaemic episodes. Moyamoya disease entails the progressive obliteration of otid arteries, thought to represent an one or both internal car autoimmune process. The development of external carotid tion collaterals produces the angiographic ‘pu ﬀ of circula smoke’ appearance from which the term derives. It presents in youth or early middle age with ischaemia or haemorrhage. Untreated, the majority of patients su ﬀ er major deﬁcit or die within 2 years. Ischaemia may be addressed by a variety of bypass techniques, for example by anastomosing the super - ﬁcial temporal artery (arising from the external carotid) to the middle cerebral artery .

Obstructive and communicating hydrocephalus

Hydrocephalus ( Figure 48.5 ) almost always reﬂects obstruc - he tion to circulation (an obstructive hydrocephalus; Figure 48.6 ) or failure of reabsorption (a communicating hydrocephalus; - Figure 48.7 ) ( Table 48.1 ). The distinction is important since obstructiv e hydrocephalus especially can cause very sudden /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF - /uni25CF

Lateral ventricle Foramen of Monro Thir d ventricle Cerebral aqueduct Fourth ventricle Figure 48.4 ‘CSF pathways’. Cerebrospinal /f_l uid (CSF) is produced by the choroid plexus of the lateral ventricles and /f_l ows through the ventricular system to exit into the subarachnoid space through the foramina of Magendie and Luschka in the fourth ventricle. TABLE 48.1 Aetiology of hydrocephalus. Obstructive Lesions within the ventricle hydrocephalus Lesions in the ventricular wall Lesions distant from the ventricle but with a mass effect Communicating Post haemorrhagic hydrocephalus CSF infection Raised CSF protein Excessive CSF Choroid plexus papilloma/carcinoma production (rare) CSF , cerebrospinal /f_l uid.

ture in this context carries a risk of herniation of the brainstem and cerebellar tonsils owing to the resulting di ﬀ erential pres sure changes (sometimes termed ‘coning’). For communicating an opening pressure and assessment of the CSF contents. It is - also therapeutic: drainage of typically between 10 and 30 /uni00A0 mL of CSF can relieve hydrocephalus temporarily . Treatment of hydrocephalus in the emergency setting usually involves CSF diversion, for example using an external ventricular drain. Disorders of CSF ﬂow with poorly under - stood mechanisms manifest in two syndromes: normal pressure hydrocephalus and idiopathic intracranial hypertension (IIH). Normal pressure hydrocephalus Normal pressure hydrocephalus is an important cause of dementia since it is readily reversible. It may be idiopathic or develop in the context of previous brain insults, including subarachnoid haemorrhage (SAH), head injury , meningitis and tumour. The CSF pressure at lumbar puncture is typically normal, but it is believed that reduced brain compliance in this condition results in transient spikes of ICP that contribute to clinical deterioration. Patients typically present with the triad of gait disturbance, incontinence and cognitive decline. V entriculomegaly is evident on imaging, but this can also be the result of cortical atrophy due to other dementia pathologies. Diagnosis typically depends on lumbar infusion and/or drainage studies to demonstrate altered compliance and/or clinical improvement associated with CSF drainage. Treatment is typically by insertion of a ventriculoperitoneal shunt.

Figure 48.5 Pathological specimen of a hydrocephalic brain. Figure 48.6 Pineal region tumour (arrow) causing obstructive hydro- cephalus. Figure 48.7 Gross hydrocephalus in a neonate with very prominent temporal horns (arrows) and fourth ventricle.

Patients with IIH develop raised ICP without an underlying mass lesion. Patients are classically young overweight women with high-pressure headaches and visual deterioration. Examination may reveal papilloedema, and occasionally cranial nerve palsies. Imaging is unremarkable, but lumbar puncture demonstrates a raised opening pressure >25 /uni00A0 mmHg. The diagnosis is one of exclusion, and the aetiology is not well understood. Impaired CSF resorption may reﬂect raised venous pressure, either as a result of sinus thrombosis or secondary to raised intra-abdominal pressure in obese patients. Weight loss and cessation of certain medications, including the oral contraceptive pill, is often e ﬀ ective. This is combined with medical therapy using acetazolamide to reduce CSF production. For patients with visual ﬁeld loss or visual failure despite medication, lumboperitoneal or ventriculoperitoneal shunting is o ﬀ ered. There may be a role for optic nerve sheath fenestration or venous sinus stenting in select cases. Summary box 48.2 Hydrocephalus and disorders of CSF ﬂow /uni25CF /uni25CF /uni25CF /uni25CF

Obstructive or communicating hydrocephalus may occur as a result of neurosurgical pathology or its treatment CT is the /f_i rst line of investigation. Lumbar puncture can con /f_i rm raised CSF pressure in communicating hydrocephalus and relieve it temporarily, but is dangerous in obstructive hydrocephalus Normal pressure hydrocephalus is a potentially reversible cause of dementia, presenting with gait disturbance, incontinence and cognitive decline IIH causes headaches and even visual loss in young people; it can be managed with weight loss, acetazolamide, serial lumbar puncture and CSF diversion as a last resort

Obstructive and communicating hydrocephalus

PRACTICAL AND ETHICAL ISSUES Creutzfeldt–Jakob dis

PRACTICAL AND ETHICAL ISSUES Creutzfeldt–Jakob disease

Creutzfeldt–Jakob disease (CJD) is a rare transmissible - spongiform encephalopathy producing a rapidly progressive dementia; it is uniformly fatal. The causative agent seems to be a misfolded protein – a prion – that is not destroyed by conventional sterilisation techniques. UK practice involves - undertaking preoperative checks to exclude any risk factors - for CJD infection. These include family history , receipt of pituitary-derived human growth hormone, receipt of cadaveric dura mater grafts and previous brain or spinal surgery prior to 1997. Where risk factors are present, instruments must be quarantined or destroyed postoperatively . PRACTICAL AND ETHICAL ISSUES Creutzfeldt–Jakob disease

PRACTICAL AND ETHICAL ISSUES Creutzfeldt–Jakob disease

Pain syndromes

Neurosurgical approaches to the relief of pain may address the underlying aetiology directly or may seek to interrupt or modu - late the transmission responsible for the pain. The contrasting An essay on the shaking pals y in 1817. nal neuralgia. This manifests, generally in middle age or later, with paroxysmal lancinating pain in the distribution of one or more divisions of the trigeminal nerve. The pain occurs with out other neurological disturbance and may be triggered b trivial stimuli such as eating or brushing the teeth. The pain is often attributable to impingement on the nerve by the superior cerebellar artery or other vessels, as ﬁrst postulated by W Dandy . Occasionally another primary lesion is responsible; for example demyelination due to multiple sclerosis can result in nerve impulses ‘jumping’ from adjacent sensory nerves to pain ﬁbres, a process termed ephaptic transmission. When medications such as gabapentin and carbamazepine cannot achieve control, surgical options include the following. /uni25CF Craniotomy and microvascular decompression (MVD): this is designed to address the proposed origin of the neuropathic pain by applying material between the nerve and adjacent vessel to prevent direct contact and stimulation. It achieves long-lasting relief of symptoms in over 90% of patients with evidence of neurovascular com pression on MRI. In other patients success rates are lower, and for older patients the risks associated with craniotomy may be hard to justify . /uni25CF Stereotactic radiosurgery is non-invasive but symp tom improvement can take weeks or months; overall e ﬃ ca cy is lower than for MVD. /uni25CF Percutaneous Gasserian rhizolysis involves needle placement under radiographic guidance at the Gasserian ganglion in Meckel’s cave. This permits lesioning of the ganglion by glycerol injection, radiofrequency thermocoagulation or balloon compression, with the aim of disrupting aberrant pain transmission. Facial numbness and recurrence of pain within 2 years are common after these procedures, and overall e ﬃ cacy is lower than for MVD. Treatment of pain elsewhere may also be based on lesion ing of nerve tracts. For example pain related to brachial plexus inﬁltration or injury may be treated by sectioning the spinotha lamic tract (cordotomy) or the dorsal r oot entry zone (DREZ operation). These approaches are limited by the potential for producing deﬁcits, and especially by the occurrence of dea ﬀ er entation (‘phantom limb’) pain syndromes, w hich are particu larly unpleasant and di ﬃ cult to treat. Electrical stimulation is used to modulate pain transmis sion: for example, spinal cord stimulators can be applied to a range of pain syndromes, especially those associated with failed spinal surgery . Deep brain stimulation targeting the periaque ductal grey and sensory thalamic n uclei has a role in chronic pain arising in the context of thalamic stroke. Implanted devices may also be used for intrathecal delivery of opiates for pain control or baclofen to alleviate spasticity . Johann Lorenz Gasser , 1723–1765, Professor of Anatomy , Vienna, Austria. Johann Friedrich Meckel (the elder), 1724–1774, German anatomist, has ‘the elder’ appended to his name to avoid confusion with his famous grandson, Johann Friedrich Meckel (1781–1833), who was also an anatomist. Hans Gerhard Creutzfeldt , 1885–1946, neurologist, Kiel, Germany . Alfons Maria Jakob , 1884–1931, neurologist, Hamburg, Germany . Functional neurosurgery - /uni25CF y /uni25CF alter /uni25CF

Intractable epilepsy can be treated surgically by implantation of a vagal nerve stimulator or by resection of one or more seizure foci Deep brain stimulation using implanted electrodes has largely replaced lesioning of these structures for management of drug-refractory Parkinson’s disease Microvascular decompression is offered for trigeminal neuralgia, and other neuropathic pain syndromes may respond to lesioning of nerve tracts

Pain syndromes

Pituitary tumours

Most tumours in the sellar region are benign pituitary adeno - mas, but pathology in this region can also include malignant variants as well as craniopharyngiomas, meningiomas, aneu - - rysms and Rathke’s cleft cysts ( Figure 48.26 ). Microadenomas are less than 10 /uni00A0 mm in size and usually present incidentally or with endocrine e ﬀ ects . Macroadenomas are larger than 10 /uni00A0 mm and often present with visual . ﬁeld deﬁcits. Thirty per cent of adenomas are prolactinomas, 20% are non-functioning, 15% secrete growth hormone and 10% secrete adrenocorticotropic hormone (ACTH). Features of note in the initial assessment include any history of galactorrhoea (suggestive of prolactinoma) and Cushingoid or acromegalic features pointing to ACTH- or growth hormone- secreting tumour s, respectively . Baseline assessment of pituitary function should include serum prolactin, follicle-stimulating hormone and luteinising hormone together with testosterone in males or oestradiol in females, thyroid function tests and fasting serum growth hormone and cortisol. Preoperative prolactin levels are crucial since prolactinomas may be managed with dopamine agonists such as bromocriptine and cabergoline rather than surgery . Growth hormone-secreting tumours may also respond to dopamine agonists or to somatostatin analogues such as octreotide. The cortisol level is also important since deﬁciency must be corrected, especially in the perioperative period. Diagnosis of ACTH-secreting tumours can be di ﬃ cult and may require the use of specialised tests such as petrosal sinus sampling and the dexamethasone suppression test. E ﬀ ective treatment requires close cooperation between the neurosurgical team and an endocrinologist. Compression of the chiasm with any evidence of visual compromise is the main indication for urgent surgical intervention. Surgical resection is usually performed b y a transsphen oidal approach through the nose, using a microscope or endo scope. Sometimes large tumours also require a craniotomy . After operation patients are at risk of CSF leak and pituitary insu ﬃ ciency . Diabetes insipidus resulting from manipulation Harvey Williams Cushing , 1869–1939, Professor of Surgery , Harvard University Medical School, Boston, MA, USA; credited as the father of modern neuro surgery; described the eponymous disease but also pioneered new techniques in bacteriology , blood pressure measurement and electrocautery . of the pituitary stalk is possible in the immediate post operative period and usually resolves spontaneously . Where it is sus - pected, the patient will require hourly measurement of urine output and blood and urine samples for calculation of sodium concentration and osmolality . If conﬁrmed, the condition can be managed with desmopressin in consultation with endocrin - ology . Pituitary apoplexy is a syndrome associated with haemorrhage or infarction in a pituitary tumour. It presents with sudden headache, visual loss and ophthalmoplegia with or without impaired conscious level. Endocrine resuscitation with intravenous steroids is the priority and surgical decompression ma y be required.

Figure 48.25 On T1-weighted magnetic resonance imaging an extra-axial, durally based lesion is seen to arise in the region of the falx. This is a meningioma. Figure 48.26 Non-functioning pituitary macroadenoma (arrow) compressing the optic chiasm superiorly, extending into the right cavernous sinus and encasing the right carotid artery.

Pituitary tumours

Posterior fossa malformations

Chiari malformations involve cerebellar herniation through the foramen magnum: /uni25CF Normal: up to 5 /uni00A0 mm of cerebellar tonsillar descent through the foramen magnum. /uni25CF Chiari I: >5 /uni00A0 mm of tonsillar descent; presents typically in young adults with cough headaches and neurological disturbance reﬂecting brainstem/cerebellar compression and/or formation of a ﬂuid-ﬁlled syrinx in the spinal cord as a result of disordered CSF ﬂow . Shunting and foramen magnum decompression are the mainstay of treatment. /uni25CF Chiari II: descent of the tonsils and vermis associated with myelomeningocele and hydrocephalus, so clinically appar ent in infancy . Dandy–Walker malformations present in infancy with macrocephaly , developmental delay and hydrocephalus; most patients have associated abnormalities in the CNS and other organ systems . Imaging demonstrates a hypoplastic cerebellar vermis, with the posterior fossa occupied by a large thin-walled cyst. Treatment usually involves shunt placement. Hans Chiari , 1851–1916, Professor of Pathological Anatomy , Strasbourg, Germany (Strasbourg was returned to France in 1918 after the end of the First World War), gave his account of this condition in 1891. Walter Edward Dandy , 1886–1946, American neurosurgeon and scientist, considered one of the founding fathers of neurosurgery . Arthur Earl Walker , 1907–1995, Canadian-born neurosurgeon, neuroscientist and epileptologist. -

Figure 48.28 An occipital encephalocele.

Posterior fossa malformations

Figure 48.28 An occipital encephalocele.

Posterior fossa malformations

Figure 48.28 An occipital encephalocele.

Presentation

Most tumours present with one or more features belonging - to three cardinal categories: these are seizure, raised ICP and focal neurological deﬁcit. Pituitary adenomas may also present with endocrine disturbance. Rachel Cowden was, in 1963, the ﬁrst patient described with the syndrome. Seizures are a common presenting feature, especially of low-grade gliomas arising in the cortical hemispheres. Simple partial seizures, involving focal twitching or similar with preserved consciousness, are the rule, but temporal location will commonly produce complex partial seizures, and any seizure may progress to a secondary generalised tonic–clonic ﬁt. Patients who have had a seizure should be started on an antiepileptic drug, typically levetiracetam. Routine prophy laxis in patients with tumours who have no history of seizures is not recommended, although a short course at the time of craniotomy for tumour excision may be warranted. Raised intracranial pressure Headache is a presenting feature in only about 50% of patients. It is classically worse in the morning and on straining (high-pressure features) and is accompanied by nausea and vomiting. Pressure e ﬀ ects develop as a result of the tumour mass e ﬀ ect and surrounding oedema, especially in fast-growing metastases and high-grade gliomas (see main section on Raised intracranial pressure ). After excluding the possibility of brain abscess (see Brain abscess and empyema ), the mass e ﬀ ect is controlled initially using high-dose glucocorticoids (e.g. dexamethasone) and, especially in the case of posterior fossa tumours, early external ventricular drainage may be required to treat obstructive hydrocephalus. Focal neurological deﬁcit A focal deﬁcit that is progressive over time, as opposed to the sudden onset of a vascular accident, is suspicious of tumour. Lesions in speciﬁc locations can produce characteristic patterns of deﬁcit due to compression of local structures ( Table 48.6 Summary box 48.9 Brain tumours /uni25CF /uni25CF /uni25CF

Most brain tumours will present with one or more features related to the following triad: Raised ICP Seizures Focal de /f_i cit

Presentation

Most brain tumours will present with one or more features related to the following triad: Raised ICP Seizures Focal de /f_i cit

Presentation

Most brain tumours will present with one or more features related to the following triad: Raised ICP Seizures Focal de /f_i cit

RAISED INTRACRANIAL PRESSURE

The importance of intracranial pressure (ICP) management in the context of head injury has been discussed elsewhere (see Chapter 28 ). Likewise ICP is key to presentation and management across the spectrum of cranial neurosurgery . RAISED INTRACRANIAL PRESSURE

Risks of craniotomy

The risks associated with craniotomy are important to appre - ciate in discussing operations with patients and family , and in evaluating patients who deteriorate postoperatively . Speciﬁc risks depend on the anatomy of each approach. T he following - ﬁgures quoted in brackets will vary signiﬁcantly between indi - vidual procedures and even between centres: - /uni25CF infection (5%) and wound breakdown; /uni25CF intracerebral haemorrhage; - /uni25CF seizures; - /uni25CF CSF leak; /uni25CF permanent neurological deﬁcit; - /uni25CF death (1%). Risks of craniotomy

Spina biﬁda occulta

A congenital absence of a spinous process, without exposure of meninges or neural tissue, but presenting a characteristic shallow hair-covered hollow at the base of the spine. This is common and rarely clinically signiﬁcant. syndrome, which involves thickening of the ﬁlum terminale, resulting in traction on the cord. Presentation is with progressive deﬁcits, spasticity , bladder dysfunction or scoliosis, and treatment involves surgical exploration and untethering of the cord. Meningocele A sac of meninges, covered by skin and containing CSF alone, herniates through an anterior or posterior bony defect. Myelomeningocele A herniating sac of meninges without covering skin contains spinal cord, nerves or both. This is always associated with Chiari II malformation (see Posterior fossa malforma tions ). Open myelomeningocele presents a high infection risk and requires early surgical repair. Lipomyelomeningocele Adipose tissue adherent to the spinal cord herniates through a bony defect to the sacrolumbar soft tissue. This may be associated with bladder dysfunction and require surgical relief of the resultant cord tethering. Failure of closure of the anterior neuropore produces anencephaly , which is uniformly fatal; the spectrum of spinal dysraphisms, however, is replica ted in the skull. Cranium bif idum is a failure of fusion, often in the occipital region. This may be associated with herniation of meninges and CSF (meningocele) and potentially also brain substance (encepha locele) ( Figure 48.28 ). Spina biﬁda occulta

Subdural empyema

Subdural empyema refers to an infected ﬂuid collection in the subdural space. This may develop as a result of sinusitis, mastoiditis or meningitis, and can complicate trauma or surgery . Figure 48.12 shows a subdural empyema associated with osteomyelitis of the frontal bone and associated scalp swelling – Pott’s pu ﬀ y tumour. In empyema, pus will generally collect in the parafalcine region and over the convexity , trigger ing inﬂammation and thrombosis in the cortical veins, which helps to explain the high mortality of 8–12%. Presentation mimics that of meningitis and cerebral abscess; typical CT appearances are of hypodense or isodense subdural collection, with contrast enhancement at the margins and often swelling and midline shift. Summary box 48.6 Subdural empyema /uni25CF /uni25CF /uni25CF

Presenting features are similar to those of meningitis or cerebral abscess Typically a crescentic collection with a contrast-enhancing rim is evident on CT Drainage is the mainstay of treatment

Subdural empyema

Presenting features are similar to those of meningitis or cerebral abscess Typically a crescentic collection with a contrast-enhancing rim is evident on CT Drainage is the mainstay of treatment

Subdural empyema

Presenting features are similar to those of meningitis or cerebral abscess Typically a crescentic collection with a contrast-enhancing rim is evident on CT Drainage is the mainstay of treatment

Surgical interventional management

Surgical/interventional management

Aneurysms may be removed from the circulation surgically by craniotomy and ‘clipping’ or by endovascular embolisation, also known as ‘coiling’ ( Figure 48.16 ). Sometimes mesh stents may also be used to help secure the metal coils within the aneu rysm sac as part of this procedure. Class 1 evidence suggests that coiling has slightly better outcomes where feasible, but clipping remains necessary or preferable in many cases; these decisions are shared between surgeons, radiologists and the ebleed risk of 4% in the ﬁrst 24 hours then 1.5% patient. A r per day thereafter is quoted for untreated aneurysms; 80% of patients who rebleed have an eventual poor outcome. For this reason, and to permit optimal management of vasospasm, the current consensus favours early intervention, despite the surgical challenges presented by brain swelling and blood load. Unruptured aneurysms represent a thorny management - - - - problem: incidentally detected small anterior circulation aneurysms represent a minimal bleeding risk. Screening, even in high-risk groups, is therefore of questionable beneﬁt.

(b) Figure 48.16 (a) A giant aneurysm of the internal carotid artery. (b) Angiographic embolisation (coiling) of the giant aneurysm. Note /uni00A0 the single displaced coil passing into the distal internal carotid artery and then the middle cerebral artery.

Surgical/interventional management

Treatment of hydrocephalus

Acute obstructive hydrocephalus is an emergency because of the risk of rapid progression to coma and death, sometimes with very sudden deterioration, a ‘hydrocephalic attack’. It may be relieved by addressing the underlying pathology , for instance by excision of a tumour responsible for an obstructive hydrocephalus. Most often, however, temporary ventricular drainage is required as a precaution in the preoperative and perioperative period or as an emergency in an obtunded or deteriorating patient. External ventricular drain External ventricular drains (EVDs) are an e ﬀ ective temporary measure to relieve hydrocephalus. Most commonly they are inserted through a burr hole at Kocher’s point (right of midline, anterior to the coronal suture), perpendicular to the brain surface, so that the catheter tip rests adjacent to the fora men of Monro in the lateral ventricle. Intrathecal antibiotics may also be delivered through the EVD. Lumbar drains are an alternative means of temporary CSF diversion. Emil Theodor Kocher , 1841–1917, Professor of Surgery , Berne, Switzerland. In 1909, he was awarded the Nobel Prize in Physiology or Medicine for his work on the thyroid. V entriculoperitoneal shunting comprises the insertion of a proximal or ventricular catheter into the lateral ventricle, while a distal catheter is tunnelled subcutaneously to the abdomen. V entriculoatrial, ventriculopleural and lumboperi - toneal shunting are also occasionally employed. A shunt valve inserted between the proximal and distal catheters regulates ﬂow through the system by opening at a predetermined pressure ( Figure 48.8 ); the shunt valve typically incorporates a CSF reservoir, which allows for percutaneous sampling. An anti-siphon system may also be incorporated to prevent exces - sive drainage in the standing position. Programmable valves o ﬀ er variable opening pressures, adjusted magnetically using a device applied externally over the valve. Shunt complications Shunts are vulnerable to disconnection, infection, blockage and overdrainage, so that 15–20% require replacement within 3 years. Features of shunt infection typically include fever, head - ache and meningism; 75% of infections present within 1 /uni00A0 month, reﬂecting introduction at the time of insertion. The diagnosis can be conﬁrmed by CSF tap from the shunt reser - voir or lumbar puncture if safe to do so. The shunt is remov ed and external ventricular drainage or serial lumbar punctures instituted to cover a course of antibiotic therapy . Once CSF sampling conﬁrms resolution of the infection and a normal protein concentration, a shunt can be inserted at a new site . Patients with blocked shunts present clinical features of hydrocephalus, which can be conﬁrmed on CT , and the shunt reservoir may be di ﬃ cult to compress or reﬁll only slowly . The - majority of blockages are attributable to cellular and protein - aceous debris, especially due to infection, but choroid plexus adhesion, blood clot or failure of the valve mechanism may also be responsible. In the context of obstructive and congenital

Figure 48.8 Examples of ventriculoperitoneal shunt valves.

because of the potential for rapid deterioration owing to uncontrolled rises in ICP . Overdrainage can result in low-pressure headaches, which are typically worse on standing. Collapse of the ventricles can cause accumulation of ﬂuid or blood in the subdural space, resulting in subdural hyg roma or subdural haematoma. The slit ventricle syndrome describes the situation in children treated with shunts, whose ventricles and subarachnoid spaces are underdeveloped, resulting in poor brain compliance. In these patients normal ﬂuctuations in ICP are exaggerated so that coughing and straining may cause symptoms of raised ICP . Any shunt blockage may not be evident on scan as the ventricles fail to enlarge. Endoscopic third ventriculostomy This procedure is especially useful in obstructive hydroceph alus due to aqueduct stenosis. A neuroendoscope is inserted into the frontal horn of the lateral ventricle and then into the third ventricle via the foramen of Monro. The ﬂoor of the ventricle is then opened between the mamillary bodies and the pituitary recess. Free drainage between the third ventricle and the adjacent subarachnoid cisterns is then possible, without the infection risk posed by implanted tubing. Reblockage of this route is common, however, and many patients will subse quently require a shunt. Rare but serious complications include damage to the basilar artery or forniceal damage, resulting in permanent memory impairment. Summary box 48.3 Treating hydrocephalus /uni25CF /uni25CF /uni25CF /uni25CF

Temporary CSF diversion can be achieved with an EVD In the long term a shunt, usually connecting the lateral ventricles with the peritoneal cavity in the abdomen (ventriculoperitoneal shunt), is the mainstay of management Shunt blockage and infection are common complications In certain cases, obstructive hydrocephalus can be managed by endoscopic third ventriculostomy

Treatment of hydrocephalus

Figure 48.8 Examples of ventriculoperitoneal shunt valves.

Treatment of hydrocephalus

Figure 48.8 Examples of ventriculoperitoneal shunt valves.

Tuberculosis

Tuberculosis (TB) infection of the central nervous system (CNS) represents haematogenous spread from primary pulmonary foci. A high index of suspicion is required, especially when population or individual risk factors are present. TB can result in a diverse but overlapping spectrum of pathology , including in the head: /uni25CF tuberculous meningitis – this commonly a ﬀ ects young chil dren; CT demonstrates intense meningeal enhancement and hydrocephalus is a common complication; /uni25CF tuberculoma – discrete tumour-like granulomas at the base of the cerebral hemispheres, presenting with mass e ﬀ ect; /uni25CF tuberculous abscess – seen predominantly in immunocom promised hosts, this represents progression of a tubercu loma with prominent central caseating necrosis; Percival Pott , 1714–1788, surgeon, St Bartholomew’s Hospital, London, UK. Besides the ‘pu ﬀ y tumour’, described in 1760, Pott established the ﬁrst association between a cancer and an environmental carcinogen, when he noted the high incidence of (squamous cell) scrotal cancers in chimney sweeps. Franz Ziehl , 1857–1926, German bacteriologist and professor in Lübeck, Germany . Friedrich Carl Adolf Neelsen , 1854–1894, German pathologist and professor at the Institute of Pathology , University of Rostock, Germany . - /uni25CF miliary tuberculosis – describes a di ﬀ use distribution of multiple small tuberculomas throughout the brain sub - stance. Where the meninges are involved, lymphocytes can be expected to predominate in the CSF , rather than the poly - morphs seen with other bacterial meningitides. The incr ease in protein content and reduction in glucose concentration are also less marked. Ziehl–Neelsen staining for mycobacteria is frequently negative, and polymerase chain reaction (PCR) testing o ﬀ ers relatively rapid diagnosis compared with culture for acid-fast bacilli, which may take weeks. A 20- to 30-mL CSF sample allows spinning to increase the culture yield. Management is with antituberculous therapy; hydrocephalus may require shunt insertion. -

Figure 48.12 Axial computed tomography scan with contrast showing a right hemisphere subdural empyema (short arrow) and a right frontal Pott’s puffy tumour (long arrow) (osteomyelitis of the frontal bone).

Tuberculosis

VASCULAR NEUROSURGERY Subarachnoid haemorrhage

‘Spontaneous’ SAH is usually the result of bleeding from a - ruptured aneurysm (approximately 80% of SAH) or an arterio - - venous malformation (A VM). Most ruptured aneurysms are located in the circle of Willis, at branch points in the arterial tree associated with turbulent blood ﬂow ( Figure 48.13 distinct subgroup of patients with SAH su ﬀ er bleeds conﬁned to the basal cisterns anterior to the midbrain and pons, without an underlying lesion evident on angiogram. This is termed perimesencephalic SAH , is believed to represent venous bleeding and has an excellent prognosis. Aneurysms may also develop as a result of infective inﬁltration of arterial walls in the context of bacteraemia (mycotic aneurysm), often in the setting of intravenous drug use or infective endocarditis. Pseudo- aneurysms may also develop after trauma or after surgery . Aneurysmal bleeding has an incidence of 10–15 per 100 /uni00A0 000 population per year. Risk factors include age, female sex, hypertension, smoking, cocaine abuse and a family his tory with two ﬁrst-degree rela tives a ﬀ ected. A range of genetic disorders, in particular adult polycystic kidney disease, ﬁbro muscular dysplasia, neuroﬁbromatosis type 1, Ehler s–Danlos and Marfan syndrome, are known to predispose patients to this condition. History and examination The typical presentation of an SAH includes a ‘thunderclap’ headache, which is both sudden and severe and is outside the patient’s normal experience. Some patients describe prod romal headaches preceding the event, potentially representing aneurysm growth or subclinical bleeds. The sudden onset occurs commonly but not exclusively during e xertion, and may be associated with seizure (10%), unresponsiveness (50%) and vomiting (70%). Sometimes it is di ﬃ cult to establish whether SAH has caused a fall or a fall with head injury is responsible for the SAH. Approximately one-third of SAHs are incorrectly diagnosed at initial presentation. Patients are then at high risk of succumbing to early complications, especially a rebleed. Thomas Willis , 1621–1675, Sedleian Professor of Natural Philosophy at Oxford. Also the ﬁrst anatomist to number the cranial nerves in the order used today . Edward Ehlers , 1863–1937, Professor of Clinical Dermatology , Copenhagen, Denmark. Henri Alexandre Danlos , 1844–1912, dermatologist, Hôpital St Louis, Paris, F Bernard Jean Antonin Marfan , 1858–1942, physician L’Hôpital des Enfants-Malades, Paris, France, described this syndrome in 1896. Albert Terson , 1867–1935, French ophthalmologist. Franciscus Sylvius , 1614–1672, a Dutch physician, chemist, physiologist and anatomist. grade’) or the patient may have focal deﬁcits and an impaired conscious level (‘poor grade’). The World Federation of Neuro - surgical Societies (WFNS) grading of SAH is measured against the condition of the patient after resuscitation rather than at the time of ictus ( Table 48.4 ). A painful third nerve palsy is typically the result of compression from a posterior communi - cating artery aneurysm. Meningitic features of neck sti ﬀ ness and photophobia often develop over hours. Intraocular haem - orrhages, classically subhyaloid, may be visible on fundoscopy . The combination of SAH and vitreous haemorrhage is known as Terson’s syndrome and occurs in 15–20% of patients. Papil - loedema should be sought, b ut may not be evident early in the course of a developing hydrocephalus. Investigation CT scan is the imaging of ﬁrst choice; when performed within 12 hours of ictus, it will conﬁrm bleeding in more than 98% of cases. This makes a diagnostic lumbar puncture unnecessary ( Figure 48.14 ). ). A - - - rance, gave his account of this condition in 1908.

Anterior cerebral communicating artery artery 36% 38% 21% Middle cerebral Posterior artery communicating artery Basilar artery 5% Posterior cerebral artery Vertebral artery Figure 48.13 Common sites of aneurysm in the circle of Willis. TABLE 48.4 World Federation of Neurosurgical Societies (WFNS) grading of subarachnoid haemorrhage. a Grade Glasgow Coma Scale Focal de /f_i cits I 15 – II 13–14 – III 13–14 + IV 7–12 ± V 3–9 ± a Focal de /f_i cit = dysphasia or limb weakness. Figure 48.14 Diffuse subarachnoid bleeding from a ruptured anterior communicating artery aneurysm extends to the prepontine and ambi

ent cisterns around the brainstem and into both Sylvian /f_i ssures.

The sensitivity of CT scan, however, deteriorates to less than 50% at 1 week after a bleed. In light of this, patients with a suggestive history and negative CT scan will require lum bar puncture, especially where presentation is delayed. The CSF supernatant should be analysed by spectrophotometry (visual inspection is not reliable) for the spectra of haemoglo bin breakdown products oxyhaemoglobin and bilirubin. These e present in samples taken at least 6 and preferably 12 /uni00A0 hours ar after SAH, but not in CSF mixed with fresh blood due to trau e to exclude matic puncture and analysed immediately . Failur SAH with an adequate lumbar puncture sample can result in diagnostic confusion and overtreatment. Aneurysms can be visualised by CT and magnetic reso gold standard remains digital nance angiography , but the subtraction angiography (DSA), which involves access to both vertebral and carotid arteries through the femoral artery under local anaesthetic. This allows visualisation of the vascular y by injection of contrast medium with simultaneous anatom radiographic screening ( Figure 48.15 ). The serious potential risks include ischaemic stroke or arterial dissection (1–2%), and renal failure or allergic reactions attributable to contrast.

Figure 48.15 There is a small saccular aneurysm of the pericallosal branch of the anterior cerebral artery.

VASCULAR NEUROSURGERY Subarachnoid haemorrhage

Anterior cerebral communicating artery artery 36% 38% 21% Middle cerebral Posterior artery communicating artery Basilar artery 5% Posterior cerebral artery Vertebral artery Figure 48.13 Common sites of aneurysm in the circle of Willis. TABLE 48.4 World Federation of Neurosurgical Societies (WFNS) grading of subarachnoid haemorrhage. a Grade Glasgow Coma Scale Focal de /f_i cits I 15 – II 13–14 – III 13–14 + IV 7–12 ± V 3–9 ± a Focal de /f_i cit = dysphasia or limb weakness. Figure 48.14 Diffuse subarachnoid bleeding from a ruptured anterior communicating artery aneurysm extends to the prepontine and ambi

ent cisterns around the brainstem and into both Sylvian /f_i ssures.

Figure 48.15 There is a small saccular aneurysm of the pericallosal branch of the anterior cerebral artery.

VASCULAR NEUROSURGERY Subarachnoid haemorrhage

Anterior cerebral communicating artery artery 36% 38% 21% Middle cerebral Posterior artery communicating artery Basilar artery 5% Posterior cerebral artery Vertebral artery Figure 48.13 Common sites of aneurysm in the circle of Willis. TABLE 48.4 World Federation of Neurosurgical Societies (WFNS) grading of subarachnoid haemorrhage. a Grade Glasgow Coma Scale Focal de /f_i cits I 15 – II 13–14 – III 13–14 + IV 7–12 ± V 3–9 ± a Focal de /f_i cit = dysphasia or limb weakness. Figure 48.14 Diffuse subarachnoid bleeding from a ruptured anterior communicating artery aneurysm extends to the prepontine and ambi

ent cisterns around the brainstem and into both Sylvian /f_i ssures.

Figure 48.15 There is a small saccular aneurysm of the pericallosal branch of the anterior cerebral artery.

Vestibular schwannoma

These are nerve sheath tumours arising in the cerebellopontine - angle ( Figure 48.27 ) that present with hearing loss, tinnitus - and balance problems. Facial numbness and weakness are less common, while large tumours may present with features of brainstem compression or hydrocephalus. The di ﬀ erential - diagnosis includes meningioma, metastasis and epidermoid cyst. Small intracanalicular tumours (within the internal audi tory canal) may be managed with surveillance. For intermediate size tumours, radiosurgery is an alternative to operation. Large lesions (>4 /uni00A0 cm), especially with brainstem compression, require excision and consideration of ventriculoperitoneal shunt to relieve hydrocephalus. Translabyrinthine, retrosigmoid and middle fossa approaches are possible, the latter options o ﬀ ering potential preservation of hearing in smaller tumours with some intact function at presentation. Patients with larger tumours will typically have no serviceable hearing in the a ﬀ ected ear and the focus is then on preserving facial nerve function. Summary box 48.11 Skull base and paediatric tumours /uni25CF /uni25CF Paediatric neurosurgery incorporates the management of tumours and developmental abnormalities, for example cysts, neural tube defects and posterior fossa malformations. In general these present with combinations of developmental delay , seizures and macrocephaly or hydrocephalus. Early fusion of one or more cranial sutures, craniosynostosis, is also a common neonatal presentation.

Figure 48.27 The appearances of a meningioma in the left cere bellopontine angle (CPA) (long arrow), with a coexisting vestibular schwannoma in the right CPA (short arrow). Pituitary tumours typically present with endocrinological disturbance (microadenomas) or visual de /f_i cits due to compression (macroadenomas). Some of these tumours are managed surgically, in close cooperation with endocrinologists Vestibular schwannomas (acoustic neuromas) are benign nerve sheath tumours, usually presenting with hearing loss, tinnitus and balance problems. Their proximity to the brainstem allows them to cause signi /f_i cant morbidity and mortality and can present a major surgical challenge

Vestibular schwannoma