16 - Dressing and constructional apraxia

Dressing and constructional apraxia

© SPMM Course 5. Visuospatial ability  Information from the visual cortex is directed towards the temporal or parietal cortex via one of the two streams. The dorsal (‘‘where’’) stream links visual information with spatial position and orientation in the parietal lobe, whereas the ventral (‘‘what’’) stream links this information to the store of semantic knowledge in the temporal lobes.  The frontal eye fields are important in directing attention towards targets in the visual field.  Neglect and constructional apraxia are disorders of visuospatial function. Neglect o Neglect of personal and extrapersonal space is usually due lesions to the right hemisphere— usually the inferior parietal or prefrontal regions. o Left side of personal and extrapersonal space is represented only on right parietal lobe, but right personal and extrapersonal space gets bilateral representation. Hence, a left-sided lesion rarely results in neglect, but right-sided lesion can result in left-sided neglect. o Deficits can be uncovered by simultaneous bilateral sensory or visual stimulation, or having the patient bisect lines of variable length. Letter and star cancellation tasks are similar, more formal tasks. o Visual neglect may produce a failure to groom one-half of body, or eat what is placed on one side of a plate. In extreme cases, patients may have anosognosia and deny they are hemiplegic or even that the affected limb belongs to them. Dressing and constructional apraxia o Although deficits in dressing and constructional ability are termed apraxias, they are best considered as visuospatial, rather than motor impairments. o Copying three-dimensional shapes such as a wire cube, interlocking pentagons (as in MMSE), or constructing a clock-face with numbers are good tests of constructional ability and may also highlight neglect if present. o Dressing apraxia is easily tested by having the patient put on clothing that has been turned inside out.