E. Lee Murray, MD

SINGLE CRANIAL NEUROPATHIES

Single cranial neuropathies are much more common than multiple cranial neuropathies but both are discussed here. The most common single cranial neuropathies are facial, abducens, oculomotor, and optic. Chapter 33 discuss ocular motor and other cranial nerve deficits in detail.

•CN 1: Olfactory

FEATURES: Loss of smell

ETIOLOGY: Trauma, degenerative disease, chemicals, aging, some brain tumors (e.g., meningioma), malnutrition

•CN 2: Ocular

FEATURES: Disturbance of vision due to prechiasmatic lesion

ETIOLOGY: Trauma; demyelination; orbital tumors; pituitary tumors; papilledema from any cause; ischemia including temporal arteritis, retinal artery ischemia; retinal vein thrombosis; infectious optic neuropathy (e.g., cat-scratch disease); optic glioma; toxic optic neuropathy (e.g., methanol, INH, and many others)

•CN 3: Oculomotor

FEATURES: Diplopia, ptosis, mydriasis

ETIOLOGY: Oculomotor nerve ischemia from diabetes or other vascular risk factors, aneurysmal compression, brainstem ischemia in multiple locations, cavernous sinus lesions of any type, intraorbital mass or inflammation, increased intracranial pressure from any reason, pineal tumor

•CN 4: Trochlear

FEATURES: Vertical diplopia, greatest with downward gaze and gaze to the opposite side

ETIOLOGY: Congenital, brainstem tumors, hydrocephalus, demyelinating disease, aneurysm especially superior cerebellar artery, intracranial hypertension from any cause, orbital tumor or inflammatory lesions

•CN 5: Trigeminal

FEATURES: Sensory loss in one or more of the trigeminal distributions: V1, V2, or V3

ETIOLOGY: Trigeminal neuralgia, tumor, trauma

•CN 6: Abducens

FEATURES: Diplopia, lateral rectus paresis

ETIOLOGY: Nerve infarction, especially with diabetes; increased intracranial pressure

•CN 7: Facial

FEATURES: Lower motoneuron facial weakness

ETIOLOGY: Bell palsy, sarcoidosis, Lyme disease; often idiopathic

•CN 8: Vestibulocochlear

FEATURES: Hearing loss, tinnitus, and/or vertigo

ETIOLOGY: Acoustic neuroma, cerebellopontine angle tumors, chronic meningitis either infectious or neoplastic, infarction,

•CN 9: Glossopharyngeal

FEATURES: Dysphagia, dysarthria, loss of taste from the posterior tongue (likely unnoticed)

ETIOLOGY: Stroke, tumor, skull-based lesions

•CN 10: Vagus

FEATURES: Dysphagia, dysarthria

ETIOLOGY: Stroke, tumors, meningitis

•CN 11: Accessory

FEATURES: Trapezius weakness, scapular winging

ETIOLOGY: Trauma, intraoperative damage

•CN 12: Hypoglossal

FEATURES: Paralysis of the tongue, deviation to the side of the lesion with protrusion

ETIOLOGY: Infarction, tumor

Although we consider cranial neuropathies as isolated entities, there are many disorders that affect multiple cranial nerves.

MULTIPLE CRANIAL NEUROPATHIES

Multiple cranial neuropathies can develop for a variety of reasons, but among the most common are neoplastic meningitis, vasculitis, and diabetes. Intrinsic lesions of the brainstem can present with multiple cranial neuropathies, but there are usually other signs of parenchymal brainstem dysfunction, including gait ataxia, unilateral or bilateral limb weakness and/or incoordination, or mental status change. Cavernous sinus lesions can result in CN 3, 4, 6, and CN 5 V1 lesions, and, sometimes, Horner syndrome.

Mononeuropathy multiplex from any cause can produce multiple cranial neuropathies although peripheral nerves are commonly affected. Causes can be neoplastic, autoimmune, vasculitis, amyloid, infectious, multifocal tumor infiltration (e.g., lymphoma), or paraneoplastic.

Disorders with multiple cranial neuropathies include:

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