Which of the following matches is incorrect regarding amnestic syndrome and site of lesion?
D. Medial temporal cortex is not supplied by the anterior communicating artery; it is supplied by the posterior cerebral artery. The anterior communicating artery supplies the basal forebrain and striatum. Wernicke–Korsakoff syndrome is usually associated with nutritional causes, where the thalamic nuclei (especially dorsal medial thalamus) are involved, leading to anterograde amnesia and confabulation. Herpes simplex encephalitis (HSE) is another cause of anterograde amnesia where anterior temporal lobes are often involved. Whether amnesia is predominantly verbal or non-verbal is determined by the side of lesion and the cerebral dominance. In CJD (Creutzfeldt–Jacob disease) diffuse cortical damage occurs. Amnesia of complex partial seizures is related to recurrent hippocampal damage and sclerosis.
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Which of the following is a component of the triad in Balint’s syndrome?
D. Balint’s syndrome consist of a triad of oculomotor apraxia (deficits in the orderly visuomotor scanning of the environment), optic ataxia (inaccurate manual reaching toward visual targets), and simultanagnosia. Pathologically, Balint’s syndrome is produced by bilateral parietooccipital lesions. Simultanagnosia is the inability to integrate visual information in the centre of gaze with more peripheral information. The patient gets stuck on the detail that falls in the centre of gaze without scanning the visual environment for additional information. They typically ‘miss the forest for the trees.’ This leads to a significant disturbance in object identification. A patient with Balint’s syndrome when shown a table lamp and asked to name the object may look at its circular base and call it an ash tray!
Features of Gerstmann’s syndrome include all of the following except:
C. Dysarthria is not a feature of Gerstmann’s syndrome. Full Gerstmann’s syndrome, though rarely reported, consists of left–right disorientation, finger agnosia, dysgraphia, and dyscalculia. The lesion is mostly attributed to a dominant parietal lobe dysfunction. When all the components are present the syndrome reliably localizes to the dominant angular gyrus. Gerstmann himself thought that the inability to calculate was because of the fact that children learnt to count with their fingers and the dysgraphia was due to problems with differential finger movements—both being secondary to finger agnosia. Gerstmann noted that the greatest trouble in finger agnostics was with distinguishing second, third, and fourth fingers. Screening for full Gerstmann’s syndrome should be performed on patients who show any single component.
Blindsight is a feature of which of the following focal cortical syndromes?
D. Anton’s syndrome features blindness and denial of blindness, that is the patient is blind but denies sightlessness. The syndrome is most commonly associated with bilateral lesions of the occipital cortex. Blind sight is a paradoxical syndrome seen in patients with cortical blindness. It is the ability of the person to orient towards visual stimuli while there is no conscious visual perception. This is due to the fact that 20 to 30% of fibres of the optic tract are directed to non-geniculate destinations, such as the superior colliculi and pretectal region of the brainstem. It is thought that some visual processing occurs in this non-geniculate system. This phenomenon is not demonstrable if the blindness is the result of pregeniculate lesions. Geschwind’s syndrome refers to personality changes proposed to be due to disconnection of brain areas noted in those with temporal lobe epilepsy. The Charcot–Wilbrand syndrome, or irreminiscence, is characterized by the inability to generate an internal mental image or revisualize (imagine) an object. The patients have more difficulty in generating objects through drawing than in copying model figures. It is usually secondary to bilateral parietal lobe lesions. Central achromatopsia refers to loss of colour vision due to occipital lobe lesions.
A patient is not able to perform sequential motor acts despite intact comprehension, muscle power, and ability to perform single-step commands.
He is exhibiting:
A. Ideational apraxia (IDA) is an inability to correctly sequence a series of acts that lead to a goal. Asking the patient to carry out a multistep, sequential task, such as preparing a sandwich for work, is a good test of IDA. It is most often associated with degenerative dementia and delirium. Ideomotor apraxia is probably the most common type of apraxia. Patients with ideomotor apraxia make spatial and temporal errors when performing learned, skilled movements including pantomimes, imitations, and using actual objects. When pantomiming the use of a screwdriver, patients with ideomotor apraxia may rotate their arm at the shoulder and fi x their elbow. In right-handed individuals ideomotor apraxia is almost always associated with left-hemisphere lesions. A variety of structures, including the corpus callosum, the inferior parietal lobe, and the premotor areas, may be involved. Patients with ideomotor apraxia can imitate actions of others (using tools/objects) but have difficulty pantomiming (in the absence of tools/objects). In patients with conduction apraxia, imitation is worse than pantomiming. The site of the lesion has not been localized (unlike conduction aphasia). Patients with conceptual apraxia make tool-selection errors.
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