Cranial nerve lesions

CN Causes of lesion Signs
1 trauma, RTI, meningitis, frontal lobe tumour ∆ smell, anosmia
2 Demyelination - Multiple sclerosis; secondary syphilis, ethambutol, neuromyelitis optica Acuity, colour vision, pupillary reflexes (RAPD)
3 ❡ DM, hypertension, giant cell arteritis; compression from posterior communicating artery aneurysm, ↑ ICP pupil “down and out” ± absent pupillary reflexes
4 trauma to orbit. Rare. cavernous sinus thrombosis pupil "down and inwards" ⇒ vertical diplopia
5 MS, Wernicke's, pontine stroke pontine stroke: small fixed pupils ± quadriparesis. loss of facial sensation
6 Trigeminal neuralgia, herpes zoster, nasopharyngeal cancer, acoustic neuroma** failure of abduction “horizontal conjugate gaze palsy”
7 Bell's palsy (LMN), Ramsay Hunt syndrome, Lyme. UMN: stroke, tumour unilat sagging of mouth, drooling, speech difficulty. Forehead sparing = UMN lesion
8 Noise damage, Paget's, Méniere's, acoustic neuroma, drugs
9 neck/basal skull trauma, brainstem lesions, neck tumours, jugular foramen lesion palatal asymmetry, impaired swallow (NB: Gag reflex: afferent = IX; efferent = X), taste
10 palatal deviation away from lesion
11 trapezius, SCM weakness
12 syringomelia, polio, stroke, bulbar palsy, TB tongue deviation towards LMN lesion; wasting, fasciculations