AAEM case report #5: Amyotrophic lateral sclerosis

A 40-year-old man presented with a gradual onset of gait unsteadiness and weakness in the arms. The stretch reflexes were normal in the upper extremities but hyperactive in the lower extremities with bilateral Babinski signs. A myelogram revealed a partial obstruction at C-5-6. Two prior electromyograms, 7 and 5 months prior to admission, reportedly showed positive waves only in two peroneal supplied muscles. Repeat electromyographic testing demonstrated normal nerve conduction velocities and needle electrode abnormalities in upper and lower extremities as well as thoracic paraspinal muscles allowing a diagnosis of amyotrophic lateral sclerosis (ALS). The importance of electromyographic testing in clinically nonaffected areas is stressed as well as its role in patients presenting with upper motor neuron signs. It is the task of the clinical electromyographer to consider other entities in the differential diagnosis, such as a multifocal motor neuropathy with conduction blocks and design the tests accordingly. The role of electromyography in the prediction of the course of ALS by assessing the degree of reinnervation is discussed. This will become increasingly important in the design of treatment trials.