A 62-year-old man undergoes resection of a large tumour in the deep temporal lobe on the right side. Postoperatively he reports difficulty seeing objects approaching from his left. Formal perimetry shows a left superior homonymous quadrantanopia. Which structure was most likely damaged?
- A Calcarine cortex below the calcarine sulcus
- B Optic radiation fibres in the parietal lobe
- C Meyer's loop in the temporal lobe ✓
- D Lateral geniculate body
Correct answer: C. Meyer's loop in the temporal lobe
Explanation
Meyer's loop consists of optic radiation fibres that sweep forward into the temporal lobe before turning back toward the occipital cortex. These fibres carry information from the contralateral superior visual quadrant, so a temporal lobe lesion gives a 'pie in the sky' contralateral superior homonymous quadrantanopia. The parietal radiations carry the inferior quadrant, which is why a dominant parietal lesion typically produces an inferior quadrantanopia instead.
Reference: Snell's Clinical Neuroanatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.