Mycoplasma pneumoniae is a small bacterium that lacks a cell wall and commonly causes upper respiratory tract infections and pneumoniae. The overall incidence of infection in the United States has been estimated at 1.7 cases/1000 people/year (38) with 6.8% of all pneumonia caused by this pathogen (39). Symptoms include fever, cough, malaise, and headache, but as many as 25% of patients are asymptomatic. Extrapulmonary manifestations do occur, with neurologic sequelae estimated in 0.1% of all cases (39). Neurologic findings are variable and include psychosis, meningitis, transverse myelitis, ataxia, peripheral neuropathies, and cranial neuropathies. Facial nerve involvement, alone or in conjunction with other neurologic sequelae, is considered rare but has been reported by several authors (40-42). Bilateral facial paralysis has also been associated with mycoplasm infections (43,44).
The mechanism of neurologic injury is uncertain, but many theories have been put forward; these include antigen-antibody reactions, microembolisms, thrombus formation, neurotoxins, and direct viral invasion of the tissue (43).
Diagnosis is often difficult and made clinically. Viral serum titers are difficult to perform, expensive, and time consuming. A fourfold rise in the specific antimycoplasma antibody is considered definitive, with titers of 1:64 or greater highly suggestive of infection. Isolation of M. pneumoniae from the sputum is also considered diagnostic. Cold agglutinins have been used but have a low sensitivity, at only 66%, with frequent false positives from other viral infections (43). Recent advances with PCR may allow for more definitive diagnosis.
Treatment is with tetracycline or erythromycin, as the organism is entirely resistant to penicillin since it lacks a cell wall. Facial nerve decompression has not been studied or discussed in the current world literature.
The prognosis is usually good, with most patients demonstrating return of the affected neurologic function within five months (43). The prognosis and time course of facial nerve involvement is thought to be similar to that of Bell's palsy.
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