Bell's palsy is the appellation commonly used to describe an acute peripheral facial palsy of unknown cause. However, the terms "Bell's palsy" and "idiopathic facial paralysis" may no longer be considered synonymous. A peripheral facial palsy is a clinical syndrome of many causes, and evaluation requires more than a superficial examination.
This review will discuss the treatment and prognosis of Bell's palsy. Other clinical aspects of this disorder are reviewed separately. (See "Bell's palsy: Pathogenesis, clinical features, and diagnosis in adults".)
PROGNOSIS AND NATURAL HISTORY
The prognosis of Bell's palsy is related to the severity of the lesion . A simple rule is that clinically incomplete lesions tend to recover. The House-Brackmann grading system (table 1) was devised both as a clinical indicator of severity and also an objective record of progress . On this scale, grades I and II have good outcomes, grades III and IV characterize moderate dysfunction, and grades V and VI portend a poor result. Other grading systems (eg, the Sunnybrook facial grading system ) are similar and sometimes favored [4-7].
Statistically, the natural history without treatment was described in a study of 1011 patients in 1982 . One-third had an incomplete paralysis, and two-thirds had complete paralysis. Overall, 85 percent showed signs of recovery within three weeks, 71 percent had complete recovery, 13 percent had slight sequelae, and 16 percent had residual weakness, synkinesis and/or contracture. Patients with incomplete lesions had a 94 percent rate of return to normal function, while only 60 percent of those with clinically complete lesions returned to normal function. Herpes zoster is associated with more severe paresis and a worse prognosis compared with "idiopathic" Bell's palsy .
The prognosis is favorable if some recovery is seen within the first 21 days of onset . A diagnosis of Bell's palsy is doubtful if some facial function - however small - has not returned within three to four months. (See "Bell's palsy: Pathogenesis, clinical features, and diagnosis in adults", section on 'Diagnosis'.)