Diagnostic value of EMG of sternocleidomastoid and trapezius in assessing bulbar lower motor neuron involvement in amyotrophic lateral sclerosis patients

Abstract

The diagnostic value of needle electromyography (EMG) of sternocleidomastoid (SCM) and trapezius (TRA) in assessing bulbar lower motor neuron involvement (LMN) remained controversial. 203 sporadic amyotrophic lateral sclerosis (ALS) patients were enrolled to assess the correlation between EMG abnormalities in SCM and TRA and bulbar LMN involvement. Additionally, difference analysis and diagnostic consistency analysis of EMG abnormalities in GEN (genioglossus), SCM, and TRA were compared. Finally, separate effects of EMG abnormalities in GEN, SCM, and TRA on diagnostic gradings were examined according to the Awaji-Shima criteria. 22 (18.2 %) and 65 (53.7 %) patients without bulbar LMN involvement showed EMG abnormalities in SCM and TRA. In contrast, 19 (23.2 %) and 11 (13.4 %) patients with bulbar LMN involvement showed normal EMG results in SCM and TRA. Multivariate logistic regression analyses showed that both EMG abnormalities in SCM and TRA were correlated with bulbar LMN involvement (P < 0.001). SCM showed electrophysiological characteristics similar to GEN when compared to TRA. However, TRA (67.0 %) showed significantly higher rates of EMG abnormalities than SCM (41.9 %) and GEN (40.4 %) in the whole study population. Reclassified diagnostic gradings showed no significant difference when evaluating EMG abnormalities in individual muscles to indicate bulbar LMN involvement (P = 0.072). EMG abnormalities in SCM and TRA could not fully represent bulbar LMN involvement but were correlated with it. It’s advisable to prioritise TRA as a better option when a patient cannot tolerate an EMG examination in the GEN. To enhance the diagnostic evaluation, an EMG examination of GEN could be served as the last choice.