Cranial Nerve Findings

Visual fields

Unilateral blindness : lesions of ipsilateral eye or nerve.
Bitemporal hemianopia : lesion to optic chiasm, usually pituitary tumour.
Homonymous hemianopia : lesion to optic tract (blindness to contralateral side of visual fields to the side of damaged optic tract).
Macular sparing : lesion to visual cortex, which sometimes spares the macular region (where the macular is represented).

Light response/accommodation

This is not normally lost in higher cortical lesions.
Afferent defect : light shines in affected eye neither and pupil constricts.
Efferent defect : affected eye does not constrict but contralateral does.
Horner's syndrome : Lesion to the sympathetic pathway causes unilateral meiosis (constriction).
Argyll-Robertson (neurosyphilis) : small constricted, accommodation reflex preserved, light reflex absent
Holmes-Adie: eye dilated (“hOlmes”)
Myotonic pupil : dilated pupil, slowly accomodating, light response absent
Unequal pupils : III nerve palsy, Argyll Robertson, Horners (SNS lesion, so small, look for ptosis & neck scars)

III

Eye points down and out.  Ptosis (levetor palpebrae superioris): due to unopposed action of VI & IV.

IV

Diplopia on descending stairs as can not look inferiorly on adduction

VI

Can not abduct eye. Diplopia on looking to affected side

VII

Can not move muscles of facial expression on affected side of face. Sparing of forehead w upper motor neuron lesion due to bilateral innervation.

VIII

Vertigo ± cochlear sx (hearing loss, tinnitus) = peripheral lesions of labyrinth.
Vertigo + diplopia = brainstem lesion.