Acute Bell's palsy: prognostic value of evoked electromyography, maximal stimulation, and other electrical tests

Thirty-seven patients with acute Bell's palsy who had complete unilateral facial paralysis were selected for this study. Evoked electromyography, conduction latency, electromyography, and nerve excitability testing was done by one author while the maximal stimulation test was done by another on each patient. The patients were examined within ten days of onset of facial paralysis and evaluated six months after onset to determine the degree of recovery of facial motor function. The results of the tests were correlated with the degree of recovery of facial motor function in each patient. Evoked electromyography and maximal stimulation tests were the most accurate electrical tests for predicting the course of acute facial paralysis when they were performed serially within the first ten days after onset. When the results of the maximal stimulation test were equal on the involved and uninvolved sides of the face, there was a 92 percent chance of complete recovery of facial function on the involved side. In those patients in whom the response to the maximal stimulation test was markedly reduced or absent, there was an 86 percent chance of incomplete recovery of facial function. When the response to evoked electromyography on the involved side was 30 percent or greater of that on the normal side, 84 percent of the patients had complete recovery of facial function; however, when the response was 25 percent or less of normal, there was an 88 percent chance of incomplete recovery. The results of evoked EMG and the maximal stimulation test agreed in 89 percent of cases in predicting the ultimate outcome of facial paralysis.