A 34-year-old woman undergoes resection of a tumour in the left anterior temporal lobe. Postoperatively she has a right superior homonymous quadrantanopia. Which structure was injured?

• A Lingual gyrus of the occipital lobe
• B Optic radiation fibres in the parietal lobe
• C Calcarine cortex above the calcarine sulcus
• D Meyer's loop in the temporal lobe ✓

Explanation

Meyer's loop carries fibres from the ipsilateral retina that represent the contralateral superior visual field; it sweeps through the temporal lobe before reaching the occipital cortex, so temporal lobectomy produces a contralateral superior quadrantanopia ('pie in the sky'). Parietal radiation fibres carry the inferior field, producing an inferior quadrantanopia if damaged, which rules out option B.

Reference: Snell's Clinical Neuroanatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.