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Pure Alexia – Disconnection Mechanism — SCE Neurology MCQ

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HardCerebrovascular DiseasePure Alexia – Disconnection MechanismSCE Neurology

A 65-year-old man with a right posterior cerebral artery infarct affecting the occipitotemporal region develops an inability to read (alexia) while retaining the ability to name and write normally. He can spell words aloud but cannot read them. He also has a right homonymous hemianopia. What is the specific localisation of the reading deficit?

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Correct answer: E — Left visual cortex destruction + splenium of corpus callosum damage — disconnecting intact right visual cortex from left angular gyrus (pure alexia without agraphia)

This is a repeated concept from earlier batches but tests a different clinical presentation. The left PCA infarct destroys the left visual cortex (causing right hemianopia) AND the splenium of the corpus callosum (preventing visual information from the intact right visual cortex from reaching the left angular gyrus for reading). Writing is preserved because the left angular gyrus and motor pathways are intact. The patient can spell aloud because auditory language pathways are intact. A: Broca area damage causes expressive aphasia. C: Wernicke damage causes receptive aphasia. D: Right parietal damage causes spatial deficits. E: Frontal eye fields control saccades.

Reference: Geschwind Disconnection Syndromes; Clinical Neuroanatomy