MRCS Review – Anatomy Q5

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Parietal lesions cause a contralateral inferior quadranopia.

Visual field defects

  • left homonymous hemianopia means visual field defect to the left, i.e. Lesion of right optic tract
  • homonymous quadrantanopias: PITS (Parietal-Inferior, Temporal-Superior)
  • incongruous defects = optic tract lesion; congruous defects = optic radiation lesion or occipital cortex

Homonymous hemianopia

  • Incongruous defects: lesion of optic tract
  • Congruous defects: lesion of optic radiation or occipital cortex
  • Macula sparing: lesion of occipital cortex

Homonymous quadrantanopias

  • Superior: lesion of temporal lobe
  • Inferior: lesion of parietal lobe
  • Mnemonic = PITS (Parietal-Inferior, Temporal-Superior)

Bitemporal hemianopia

  • Lesion of optic chiasm
  • Upper quadrant defect > lower quadrant defect = inferior chiasmal compression, commonly a pituitary tumour
  • Lower quadrant defect > upper quadrant defect = superior chiasmal compression, commonly a craniopharyngioma

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