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Alexia without agraphia — MRCPsych Paper A MCQ

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HardNeuroanatomyAlexia without agraphiaMRCPsych Paper A

A 64-year-old right-handed man develops a right homonymous hemianopia following a left posterior cerebral artery infarction. Speech, auditory comprehension, naming, repetition and writing to dictation remain intact. He cannot read printed words or what he has just written, although he can recognise non-verbal visual objects. Which mechanism best accounts for this deficit?

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Correct answer: E — Disconnection of visual cortices from dominant temporoparietal language areas

Explanation lettering: C = shown as B · B = shown as C

This is **alexia without agraphia (pure alexia)**, a visual–language disconnection syndrome. A dominant left occipital lesion causes the right homonymous hemianopia, while splenial or related posterior white-matter involvement prevents visual information processed by the intact right visual cortex from reaching dominant temporoparietal language areas. The language and writing networks remain functional, explaining preserved speech and writing, including writing that the patient cannot subsequently read. Destruction of the dominant angular gyrus (B) would usually also impair writing, producing alexia with agraphia. A non-dominant inferior parietal lesion (D) is associated with visuospatial neglect or constructional impairment. Bilateral hippocampal circuit damage (C) causes severe anterograde amnesia. Frontal eye field–pontine disconnection (A) produces a gaze palsy rather than selective loss of reading.

Reference: Jauregui R, Greenberg J, Kuball P, et al. Alexia without agraphia: from infarctions to malignancies. Practical Neurology. 2025;25(3):246. https://pn.bmj.com/content/25/3/246