A patient has a lesion of the right parietal lobe (supramarginal gyrus, Brodmann area 40). The expected deficit would be:

• A Left hemispatial neglect and constructional apraxia (in the non-dominant hemisphere) ✓
• B Expressive (Broca's) aphasia with spared comprehension
• C Left homonymous hemianopia from optic radiation involvement
• D Gerstmann syndrome (finger agnosia, acalculia, agraphia, left-right confusion) — in the dominant hemisphere

Explanation

Gerstmann syndrome (finger agnosia, acalculia, agraphia, and left-right disorientation) results from dominant (left) angular gyrus (Brodmann area 39) lesions — not the supramarginal gyrus. A right (non-dominant) parietal lobe lesion affecting the supramarginal gyrus (area 40) and surrounding cortex produces left hemispatial neglect, dressing apraxia, constructional apraxia, and sensory extinction. Lesions of the right parietal cortex may also cause anosognosia (unawareness of deficits). Optic radiation lesions produce contralateral homonymous visual field defects but this is a secondary feature, not the primary deficit of a supramarginal gyrus lesion.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.