Upper trapezius electromyography aids in the early diagnosis of bulbar involvement in amyotrophic lateral sclerosis

Electromyography (EMG), particularly measurements of the tongue or sternocleidomastoid, aids in the diagnosis of amyotrophic lateral sclerosis (ALS) and may be used to identify lower motor neuron lesions in the bulbar region. Abnormal trapezius EMG recordings were recently shown to be useful in diagnosing ALS. Here, we investigated the role of upper trapezius EMG in assessing bulbar involvement in ALS. Standard EMG measurements were recorded from the upper trapezius in ALS, cervical spondylotic myelopathy (CSM), and normal controls (NC). Forty-three CSM patients were examined pre-operatively and three months post-operatively. Greater spontaneous activity levels were observed in upper trapezius EMG measurements of ALS patients with a disease duration of ≤8 months (70%), compared with patients with a disease duration of >8 months (40%). Significant differences in motor unit action potential parameters were also noted between ALS and CSM or NC. Fewer spontaneous EMG recordings were detected in CSM post-operatively. Furthermore, no differences in neurogenic EMG measurements were observed in ALS between the trapezius and sternocleidomastoid muscles (p = 0.22). In conclusion, upper trapezius EMG recordings may provide valuable information for assessing the clinical and subclinical involvement of bulbar lower motor neurons in ALS patients, particularly at early disease stages.