Cranial Nerves Anatomy

Question 1

Monocular visual loss

Answer 1

optic nerve pathology

Question 2

Bitemporal heteronymous hemianopsia (bilateral temporal visual fields)

Answer 2

Optic chiasm pathology

Question 3

Homonymous hemianopsia ((vision loss in c/l eye))

Answer 3

Retrochiasmal pathology

Question 4

Papilledema

Answer 4

flattening of posterior sclera, tortuosity and elongation of intraorbital optic nerves, dilatation of perioptic SAS

Question 5

Anosmia

Answer 5

CN1 dysfunction u/l

Look for cribiform plate fx or shear forces, anterior temporal lobe injury

Question 6

Esthesioneuroblastoma

Answer 6

arises from olfactory epithelium in nasal vault

Question 7

CN3 neuropathy

Answer 7

1. Uncal herniation pushes CN3 on petroclinoid ligament
2. PCA aneurysms can compress
   - -> check for pupillary involvement (parasympathetic fibers are peripherally distributed)

Question 8

Simple CN3 neuropathy with pupillary sparing

Answer 8

presumed microvascular infarction involves vessels supplying core of nerve with relative sparing of peripheral pupillary fibers

Question 9

Oculomotor ophthalmoplegia

Answer 9

strabismus, ptosis, pupillary dilatation, downward abducted globe and paralysis of accommodation

Question 10

Simple CN4 neuropathy (isolated)

Answer 10

• trauma
• injury by free edge of tentorium cerebelli or from PCA/SCA aneurysm
• contusion of superior medullary velum

Question 11

Complex CN4 neuropathy

Answer 11

• assoc with other CN injury, CN3, CN6)
• brainstem stroke or tumor
• cavernous sinus thrombosis, tumor
• orbital tumor

Question 12

Paralysis of superior oblique muslce

Answer 12

Extorsion (outward rotation) due to unopposed action of inferior oblique muscle

-diplopia, weakness of downward gaze, neck pain fr head tilting

Question 13

Proximal V3 injury

Answer 13

motor atrophy of masticator muslces

Question 14

Distal V3 injury

Answer 14

(above mylohyoid nerve takeoff)

Affects only anterior belly of digastric and mylohyoid