- Function
- Stabilizes gaze: Head rotates one way → Eyes move opposite.
- Pathway: Semicircular Canal → CN VIII → Vestibular Nucleus → Contralateral PPRF/CN VI → MLF → Ipsilateral CN III.
- Clinical Testing
- Oculocephalic (“Doll’s Eyes”) Reflex:
- Assess brainstem in coma.
- Eyes move opposite to head rotation = Intact brainstem.
- Eyes fixed = Brainstem lesion.
- Caloric Stimulation (COWS):
- Describes fast phase (nystagmus).
- Cold water = Opposite.
- Warm water = Same.
- Pathology: Internuclear Ophthalmoplegia (INO)
- Lesion: MLF (Medial Longitudinal Fasciculus).
- Deficit: Ipsilateral eye cannot adduct on lateral gaze; contralateral eye has nystagmus.
- Key Feature: Convergence is preserved (bypasses MLF).
- Etiology: Multiple Sclerosis (Young/Bilateral), Stroke (Elderly/Unilateral).