Prognostic value of EMG genioglossus involvement in amyotrophic lateral sclerosis

Objective: To evaluate the prognostic value of needle electromyography (EMG) genioglossus involvement in patients with amyotrophic lateral sclerosis (ALS) at diagnosis. Methods: We separately explored the prognostic value of clinical bulbar lower motor neuron (LMN) signs and EMG genioglossus involvement using Cox proportional hazard models adjusted for age, gender, diagnostic delay, presence of bulbar upper motor neuron (UMN) signs, EMG cervical and lumbosacral region involvement, ALSFRS-R score and C9Orf72 gene status. Then, we compared the prognostic value of EMG masseter and genioglossus abnormalities in a subset of patients in whom both muscles were analysed. Results: 103 ALS patients were included in the study. Neurophysiological genioglossus involvement was associated with a shorter survival (p = 0.002), a shorter time to moderate dysphagia (p = 0.0001) and to severe dysarthria (p = 0.012). Its prognostic value was still evident in patients without clinical bulbar LMN signs. Bulbar clinical LMN signs were only associated with an earlier onset of moderate dysphagia (p = 0.0001). EMG masseter abnormalities did not reach statistical significance with regard to all the clinical milestones. Conclusions: Genioglossus EMG at diagnosis could provide important information about ALS progression rate. The masseter muscle seems to be less involved in ALS. Significance: EMG genioglossus involvement is a prognostic factor in ALS.