Alexia Without Agraphia
Alexia without agraphia is a disconnection syndrome where patients cannot read but can write. A left posterior cerebral artery occlusion is the most common cause, leading to infarction of the dominant occipital lobe that extends into the splenium of the corpus callosum. Due to this infarction, there is no visual information perceived by the dominant occipital lobe to send to the angular gyrus (the reading center).
Visual information from the non-dominant occipital lobe is unable to cross via the splenium of the corpus callosum to the angular gyrus due to its infarction. In addition to being unable to read but able to write, patients will have intact comprehension and production of oral speech and may have a right homonymous hemianopsia or right hemiachromatopsia.
Pathophysiology:
PCA Infarct (most common)
• occipital lobe involvement
→ contralateral homonymous hemianopsia
→ no visual information from the dominant occipital lobe to the angular gyrus
• splenium involvement
→ visual information from the non-dominant visual cortex cannot communicate to the angular gyrus
Clinical Presentation:
1. R. homonymous hemianopsia (often)
2. Inability to understand what is being read (alexia)
3. Able to write (without agraphia)
Moises Dominguez, MD @MoiseyWoisey
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