Bell's palsy is an acute, unilateral paresis or paralysis of the face in a pattern consistent with peripheral nerve dysfunction without any other detectable cause. Accompanying symptoms may include pain in or behind the ear, numbness in the affected region, hyperacusis and disturbed taste on the ipsilateral tongue. Men and women, most commonly between 10 and 40 years of age, are equally affected. There is no preference for either side of the face. The etiology is unclear, but recent isolation of herpes simplex virus-1 genome from facial nerve endoneuronal fluid in persons with Bell's palsy supports a viral cause. Most persons with this condition achieve full spontaneous recovery. Clear improvement usually begins within three weeks but may require three to six months. In one large study, 71 percent of patients with Bell's palsy recovered normal facial function, 13 percent had insignificant sequelae and 16 percent had permanently affected facial function with contracture or involuntary movements. Marson and Salinas reviewed the evidence on treatment of persons with Bell's palsy to determine the optimal way to maximize facial recovery and reduce risks of sequelae with minimal adverse effects.

A review of randomized, controlled trials using steroids showed no increase in the proportion of patients achieving good recovery. Results from one randomized controlled study revealed that prednisone was better than acyclovir in improving recovery of facial motor function, although the study was of poor quality. Results from one randomized, controlled study revealed that acyclovir was better than placebo in improving facial motor function in people taking prednisone. No serious side effects were noted in these studies.

The authors conclude that there is no strong evidence indicating that steroids provide long-term benefit in patients with Bell's palsy. Although results from one good study reported that prednisone was better than acyclovir in improving facial motor recovery and another demonstrated that acyclovir was better than placebo when added to prednisone in improving facial motor recovery, the authors do not find enough evidence to support any specific treatment for Bell's palsy.