Evoked Electromyography and Idiopathic Facial Paralysis

Abstract

The purpose of this study was to standardize and evaluate the results of evoked electromyography (EEMG) in normal patients and in patients with acute idiopathic facial paralysis. A comparison of the amplitude of response to EEMG from one side of the face to the other in 288 normal patients yielded a great variability in results. The amplitude difference was not greater than 50%, and therefore a difference of less than 50% was considered normal. Test-retest variability of the percentage difference in amplitude in 10 subjects showed a 10% variation in seven patients and up to a 20% variation in the remaining three patients. Fifty patients with acute idiopathic facial paralysis were seen within 14 days of onset. A favorable prognosis was based on an EEMG amplitude of more than 25% of the normal side. With this criterion EEMG was accurate in predicting complete recovery in 36 (92%) of 39 patients. When EEMG was 25% of normal or less, incomplete recovery occurred in 9 (82%) of 11 patients. The response was 0% to 10% in six patients; four had a poor recovery and the remaining two had a fair recovery. The technique, interpretation of results, avoidance of pitfalls, and shortcomings of this test are discussed.