Electrophysiologic Pattern of Facial Muscle Involvement in Bell's Palsy

Abstract

Introduction: Idiopathic Bell's Palsy is the commonest cause of Facial nerve palsy accounting for 45% to 71% of all causes of Facial Palsy. Electrophysiological evaluation comprises of Nerve conduction studies(NCS), Blink response and Electromyography(EMG) Methods: This was a prospective cross-sectional study done among 50 consecutive patients with Bell's Palsy who were evaluated and diagnosed within 1 week after onset of symptoms. Patients with facial palsy with a normal MRI and normal hematological and biochemical parameters were labelled as Bell's Palsy and were subjected to an NCS. Latency and CMAP recordings were obtained from Orbicularis Oculi, Nasalis and Orbicularis Oris. Results: Fifty patients were included in this study (27 male and 23 female). Most patients belonged to the age group of 41 - 60 years. One-Half(25) of the included patients had palsy of the Facial nerve on the right side and the others on the Left side. Forty-one(82%) of included patients had electrophysiological involvement of the orbicularis oculi as dened by a decrease in CMAP of more than 50% compared to the normal side. Similarly, 41(82%) patients had electrophysiological abnormality of the Nasalis muscle and 26(52%) patients had decreased CMAP of the Orbicularis Oris Muscle. The most frequent electrophysiologic pattern observed in this study in the rst week was involvement of all 3 muscles studied i.e., Orbicularis Oculi, Nasalis and Orbicularis Oris. Conclusion: In the rst week of illness, electrophysiological abnormality was most frequently seen in Orbicularis Oculi and Nasalis muscles. Follow-up electrophysiological studies are required to know the pattern of progression