Other Causes of Facial Palsy
Lyme disease commonly involves the facial nerve, as indicated in Chap. 31. The mechanism is uncertain but there is, so far, no evidence of direct spirochetal infection of the nerve. The diagnosis is likely when there has been a tick bite with well-documented erythema migrans or arthritis. Several of our Lyme-infected patients have had almost simultaneous facial palsy and mild distal sensory polyneuropathy. HIV infection is another well-known infectious cause of facial palsy. The facial palsy of both Lyme and HIV infections is associated with a pleocytosis in the spinal fluid, for which reason serologic and CSF examination may be useful if there is suspicion of either process. Rarely, chicken pox in children may be followed in 1 to 2 weeks by facial paralysis. Tuberculous infection of the mastoid and middle ear or of the petrous bone is a cause of facial paralysis in parts of the world where this infection is particularly common. Facial palsy may occur during or soon after infectious mononucleosis and was observed occasionally in poliomyelitis. The facial nerve is also frequently involved in leprosy. Bilateral involvement of the facial nerve is commented on below. The nerve is often involved in sarcoidosis, where the lesion is probably in the meninges as discussed in the following section.
The Ramsay Hunt syndrome, caused by herpes zoster of the geniculate ganglion, consists of a facial palsy associated with a vesicular eruption in the external auditory canal, other parts of the cranial integument, and mucous membrane of the oropharynx. This infection may be initially indistinguishable from Bell’s palsy as the vesicles may not become apparent for days. Often the eighth cranial nerve is affected as well, causing nausea, vertigo, and deafness. Murakami and colleagues (1998) showed that the virus can be detected even before the emergence of typical vesicles by collecting exudate from the skin of the pinna on a Schirmer strip (otherwise used to quantitate tearing) and applying polymerase chain reaction (PCR) techniques. In this way, in a matter of a few hours, they documented VZV infection in 71 percent of patients with Ramsay Hunt syndrome without vesicles. Currently, treatment with acyclovir, valacyclovir, or famciclovir is recommended. The randomized trial by Whitley et al and review by Sweeney and Gilden are recommended to the interested reader.
Tumors of the parotid gland or ones that invade the temporal bone (carotid body, cholesteatoma, and dermoid) or granulomatosis including the earlier mentioned sarcoidosis, or pachymeningitis at the base of the brain may produce a facial palsy; the onset is insidious and the course progressive. Fracture of the temporal bone (usually with damage to the middle or internal ear), otitis media, and middle ear surgery are uncommon causes. The orientation of the petrous fracture determines the prognosis (see discussion in Chap. 34). Acoustic neuromas, neurofibromas, glomus jugulare tumors, and aneurysmal dilatations of the vertebral or basilar artery may involve the facial nerve. Pontine lesions, most often vascular or neoplastic, cause facial palsy, usually in conjunction with other neurologic signs. Weakness of only a portion of the facial musculature, associated with numbness in the same region, may be the result of perineural tumor invasion by squamous cell or other skin cancers (see further on under “Multiple Cranial Nerve Palsies”). An autosomal dominant syndrome of facial palsy, multiple truncal café-au-lait spots and mild developmental delay was described by Johnson and colleagues.