09 - E. Abnormalities in physiological drives

E. Abnormalities in physiological drives

© SPMM Course Thalamic pain syndrome can occur in cases of stroke involving thalamoperforating branches of posterior cerebral artery. Patients have contralateral loss of sensation with burning or aching pain triggered by light cutaneous stimulation. D. Thirst Subfornical organ (SFO) and organum vasculosum of the lamina terminalis (OVLT) are circumventricular organs playing a crucial role in the perception of thirst. The hypothalamic paraventricular nucleus is also involved in the regulation of thirst. Angiotensin II acts as a neurotransmitter to propagate thirst signals to hypothalamus. Hypotension also stimulates thirst through pathways originating from the baroreceptors on aorta and carotid. Anti diuretic hormone (ADH) increases water reabsorption at renal tubules and thus helps maintain body’s fluid balance. The syndrome of inappropriate secretion of ADH (SIADH) may result from damage to paraventricular and supraoptic hypothalamic nuclei, or due to the use of drugs such as carbamazepine or chlorpromazine. Some tumours such as carcinoma of lung can also produce excess ADH. Low sodium and reduced osmolarity is noted in the presence of normal renal excretion of sodium and high urine osmolality. E. Abnormalities in physiological drives Disorder Clinical features Kluver-Bucy syndrome Bilateral lesions of amygdala and hippocampus results in placidity with decreased aggressive behaviour. Prominent oral exploratory behaviour and hypersexuality. Hypermetamorphosis (objects are repeatedly examined as if they were novel) is also seen. LaurenceMoon-Biedl Syndrome Obesity and hypogonadism along with low IQ, retinitis pigmentosa, and polydactyly. Diabetes insipidus is also seen. Autosomal recessive with genetic locus at 11q13 in most cases. No hypothalamic lesions have been found. Prader-Willi Syndrome Hypotonia, obesity with hyperphagia, hypogenitalism, mental retardation, short stature, impaired glucose tolerance. Abnormal control of body temperature and daytime hypersomnolence is related to hypothalamic disturbances. A reduction in oxytocin neurons and satiety neurons is noted. Associated with paternal deletion (genomic imprinting) at 15q11-q13 Kleine-Levin Syndrome Compulsive eating behaviour with hyperphagia, hypersomnolence, hyperactivity, hypersexuality and exhibitionism. A hypothalamic abnormality sometimes preceded by a viral illness; often resolves by the third decade of life. Psychogenic polydipsia Excessive water consumption in the absence of hypovolemia or hypernatremia. May lead to water intoxication and serious electrolyte imbalance.