Prognostic Value of Elactrophysiologic Tests in Bell's Palsy

Moon, Duk Hong; Sa, Eun Hi; Yun, Young Jin; Lee, Dong Jo; Hong, Seong Uk

Abstract

Bell's palsy is a relatively common, unilateral facial paralysis of unknown etiology. The purpose of this study was to evaluate the prognostic value of several electrophysiologic tests in Bell's palsy. Blink reflex (BR), side-to-side compound muscle action potential (CMAP) amplitude comparison, and side-to-side nerve excitability test (NET) threshold differ once have been studied during the first 2 weeks in 66 patients with Bell's palsy. According to the early response of BR(Rl), the patients were divided into 3 groups: Rl< or = 13ms(17cases) ; Rl>13ms(22cases), and absent BR(27cases). There was a remarkable tendency towards a satisfactory recovery from paralysis if BR occurred during the first 2 weeks from onset(p<0.001). In patients with normal BR, 88.2% had a satisfactory recovery, when the reflex was absent a bad prognosis was given in 59.3% of the patients. According to side-to-side CMAP amplitude comparison, the patients were divided into 2 groups; CMAP amplitude comparison > or = 25% (35cases), and CMAP amplitude comparison <25% (31cases). There was a tendency towards a satisfactory recovery from paralysis if side-to-side CMAP amplitude comparison was more than 25% (p < 0,003). In patients with more than 25% of CMAP amplitude comparison, 82.9% of the patients had a satisfactory recovery, but in patients with less than 25% of CMAP amplitude comparison, 51.6% of the patients had a bad prognosis. According to side-to-side NET threshold difference, the patients were divided into 2 groups, NET threshold difference < or = 3.5mA(43cases), and NET threshold difference >3.5mA (23cases). When the threshold of electrical excitability on both sides differs 3.5mA or more an unsatisfactory recovery has strongly to expected(p<0.001). In patients with less than 3.5mA of NET threshold, 81.4% had a satisfactory recovery, but in patients with more than 3.5mA of NET threshold, 60.9% had a bad prognosis. BR, side-to-side CMAP amplitude comparison, and side-to-side NET threshold difference seem to be useful independent indices for predicting the prognosis an early stage of the paralysis.