The spectrum of electrophysiological abnormalities in Bell's palsy

Background: As part of an investigation of a suspected "outbreak" of Bell's palsy in the Greater Toronto Area, a population-based sample of patients w ith Bell's palsy was investigated electrophysiologically to help understand the spectrum of abnormalities that can be seen in this setting. Methods: T wo hundred and twenty-four patients were surveyed, of whom 91 underwent for mal neurological assessment. Of the latter, 44 were studied electrophysiolo gically using standard techniques. Thirty-two of the 44 patients fulfilled clinical criteria for Bell's palsy. Results: A wide range of electrophysiol ogical changes was observed. Blink responses were the most useful test show ing diagnostic sensitivity of 81% and specificity of 94% compared to the co ntralateral control side. Needle electromyography was additionally helpful in only one patient of six with normal conduction studies. Conclusions: The re is a wide spectrum of electrophysiological abnormalities in Bell's palsy . Blink reflex latencies may be under-utilized in the assessment of the fac ial nerve in Bell's palsy. Facial EMG is not generally useful in routine as sessment.