What arteries are likely affected in a right-handed adult patient with a 2-day history of stroke, presenting with alexia without agraphia, characterized by an inability to read but preserved ability to write sentences?

Alexia Without Agraphia: Left Posterior Cerebral Artery Territory

This patient has alexia without agraphia caused by infarction in the left posterior cerebral artery (PCA) territory, specifically involving the left occipital lobe and splenium of the corpus callosum.

Arterial Territory and Anatomical Substrate

The left PCA supplies the critical structures damaged in this disconnection syndrome 1, 2:

• Left occipital lobe (including the visual word form area in the medial occipitotemporal gyrus)
• Splenium of the corpus callosum
• Often extends to the left fusiform gyrus and left forceps major 3

The right-hand dominance confirms left hemisphere language dominance in this patient, making the left PCA territory stroke the culprit 1.

Pathophysiology of the Reading-Writing Dissociation

The preserved writing with absent reading occurs because visual information from both hemispheres cannot reach the intact left hemisphere language areas 1, 2:

• The left occipital lobe damage destroys the visual word form area, eliminating direct visual input to left hemisphere reading centers 1
• The splenial lesion blocks visual information from the intact right occipital lobe from crossing to reach left hemisphere language areas 2
• Writing remains intact because motor output pathways from left hemisphere language areas to the hand are preserved 1

Imaging Findings to Expect

Brain MRI in this syndrome typically demonstrates 1, 2, 3:

• Acute infarct of the left occipital lobe (involving the visual word form area)
• Involvement of the splenium of the corpus callosum
• Possible extension to posterior thalamus 1
• Variable involvement of left fusiform gyrus and left forceps major 3

Recent evidence shows that 89% of left PCA stroke patients WITHOUT alexia lack involvement of these three critical regions (splenium, left forceps major, left fusiform gyrus), while patients WITH alexia have various combinations of damage to these structures 3.

Associated Deficits

Right homonymous hemianopia is the expected visual field defect 1:

• Results from left occipital lobe damage affecting the visual cortex
• Does not explain the reading deficit, as visual acuity remains grossly normal 1, 2

Clinical Pitfall to Avoid

Do not assume atypical hemispheric dominance explains unexpected reading patterns 4. While exceptionally rare cases of right-handed individuals with right hemisphere language dominance exist, the standard left PCA territory involvement in a right-handed patient is the overwhelmingly likely explanation 1, 2.

Rehabilitation Considerations

Speech-language pathology evaluation should occur as early as possible, as treatment outcomes are superior when begun in the acute stage 5. The goals include facilitating recovery of reading abilities, developing compensatory strategies, and providing assistive communication supports ranging from low-tech to high-tech devices 5.