Teaching NeuroImages: somatic muscle fasciculations detected by electrocardiography.

A routine EKG during admission for gastrostomy in a chronically hypertensive 75-year-old patient with amyotrophic lateral sclerosis (ALS) demonstrated repetitive small depolarizations (figure). The patient had no cardiac pacemaker and was not taking any medication. A study of 550 routine EKGs revealed somatic muscle fasciculation potentials in 1%, in association with a range of lower motor neuron pathology, including postpoliomyelitis and spondylosis. Such potentials were consistently detected in EKGs of those known to have neuromuscular disorders.1 Although fasciculations are a hallmark sign in ALS, they are rarely the initially reported symptom, in contrast to those with benign fasciculations. A study by Mills2 reviewed the waveforms in both. Fasciculations noted on EKG should prompt a search for the underlying cause.