Optimizing muscle selection for electromyography in amyotrophic lateral sclerosis

Introduction: We compared the yield of limb and thoracic paraspinal muscle examination for revealing lower motor neuron (LMN) dysfunction on electromyography (EMG) in amyotrophic lateral sclerosis (ALS). Methods: A retrospective review of 354 patients with clinically definite or probable ALS was performed. Seventeen limb muscles and thoracic paraspinal muscles were evaluated for the presence of both active and chronic denervation. Results: Distal limb muscles showed the highest electrodiagnostic sensitivities of LMN dysfunction in ALS regardless of onset region and diagnostic certainty at the time of diagnosis. Electrodiagnostic yield is higher in muscles from the onset limb. Noncontiguous spread of lower motor neuron degeneration is present in ALS. Optimally selected 6 upper and 5 lower extremity muscles yielded >98% of potential positive cervical or lumbosacral segments. Conclusions: An algorithmic approach to needle EMG in ALS based on pretest probability of individual muscles optimizes electrodiagnostic yield, thus possibly minimizing test duration and patient discomfort. Muscle Nerve 56: 36–44, 2017.