The Spectrum of Electrophysiological Abnormalities in Bell's Palsy

Abstract

ABSTRACT: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 with Bell's palsy was investigated electrophysiologically to help understand the spectrum of abnormalities that can be seen in this setting.Methods:Two hundred and twenty-four patients were surveyed, of whom 91 underwent formal neurological assessment. Of the latter, 44 were studied electrophysiologically using standard techniques. Thirty-two of the 44 patients fulfilled clinical criteria for Bell's palsy.Results:A wide range of electrophysiological changes was observed. Blink responses were the most useful test showing diagnostic sensitivity of 81% and specificity of 94% compared to the contralateral control side. Needle electromyography was additionally helpful in only one patient of six with normal conduction studies.Conclusions:There is a wide spectrum of electrophysiological abnormalities in Bell's palsy. Blink reflex latencies may be under-utilized in the assessment of the facial nerve in Bell's palsy. Facial EMG is not generally useful in routine assessment.

Annualized Incidence and Spectrum of Illness from an Outbreak Investigation of Bell’s Palsy

“…Where indicated, contralateral EMG was performed. Details of electrophysiological examinations have been published [14].…”

Prognostic factors of Bell's palsy: Multivariate analysis of electrophysiological findings

“…It is the most frequent form of peripheral palsy of the facial nerve (FN), representing about 50% to 60% of all etiologies, with a variable annual incidence of 8 to 52.8 new cases/100.000 subjects. [1][2][3] Predictability of facial nerve paralysis outcomes are of essential importance for patient counseling and are a guide for clinical management. The higher percentage and shorter time of recovery is achieved when corticosteroid therapy, [2][3][4] surgical decompression of the facial nerve, 5 and rehabilitation 6 are administered within the most favorable time frame.…”

“…Several electrophysiological tests have been used to determine FP prognosis: electroneurography (ENoG), blink reflex test (BR), and needle electromyography (EMG) are the most frequently studied. Data on the prospective predictive value of such tests are conflicting, mainly due to selection biases: etiology and degree of palsy [8][9][10][11][12] ; tests involved and ENoG cutoff value 8,10,11,13,14 ; initial timing for evaluation being between 5 to 10 days postonset 10,14,15 or otherwise 3,8,[11][12]16 ; prognostic follow-up time set at 6 to 12 months, 8,[10][11][12]17,18 or shorter. 12,15 Clinical predictors have been implemented to improve prognosis, 19,20 but these studies also are affected by biases linked to small study samples, 19 patient selection, and follow-up.…”

Facial Palsy: A Retrospective Study of 416 Cases Based on Electrodiagnostic Consultation

“…The BR reflex (R1 latency values) is less frequently used as a prognostic tool in FP [19] because it is more frequently absent than CMAPs. However, in 4 patients of our series, CMAPs were not obtained in the OOc muscle, and an R1 with increased latency was found in the same muscle.…”

“…Later, needle Electromyography (EMG) can reveal small amplitude and short duration Motor Unit Action Potentials (MUAPs), typical for ongoing reinnervation [18,19]. Finally, the Blink Reflex (BR) evaluation of the R1 latency, by stimulating the supraorbital nerve and recording from the OOc muscle, allows the entire efferent peripheral pathway of the facial nerve to be studied on the affected side [19,20]; the R1 potential is absent in the presence of a transmission block [21]. It is also very useful to rule out diffuse demyelination (e.g., autoimmune neuropathies).…”