Q32 - Disorders Of Optic Chiasm

Question 1

Chiasmal anatomy and relation to pathologies

Answer 1

• general symptoms of optic nerve disorders are ipsilateral (same side) decrease in visual acuity.
• optic chiasm lie on stellar diaphragm. Pituitary gland lies inferiorly, int carotid lies laterally and hypothalamus+Ant lobe lies superiorly.
  1) Inferior nasal field can be affected by pituitary tumors
  2) superior nasal field can be affected by craniopharyngomas
  3) temporal field can be affected by ex aneurysms

Question 2

Pituitary adenomas

Answer 2

• can via mass effect cause compression of inferior nasal fields, leading to bitemporal superior quadrantopia (loss of both temporal superior quadrants) -> bitemporal hemianopia (loss of vision in both temporal visual fields).

Question 3

Craniopharyngomas

Answer 3

• Slow growing tumors developing from pouch of rathke, growing along stem of pituitary gland -> compress superior nasal fibers -> bitemporal inferior quadrantopia -> bitemporal hemianopia.

Question 4

Aneurysms

Answer 4

• causes lateral compression, mainly affecting temporal fibers -> unilateral nasal hemianopia -> binasal hemianopia (compression of contralateral side).

Question 5

Meningiomas

Answer 5

• Can affect different parts of chiasm depending on point of origin. Ex from Sella turcica -> compress optic nerve or chiasm -> ipsilateral central scotoma + contralateral defects of superior temporal quadrant.