Eaton-Lambert syndrome: reflex improvement with guanidine.

A 46-year-old man with typical clinical and electrophysiologic findings of the Eaton-Lambert syndrome did not have muscle stretch or H reflexes. With guanidine treatment (42.0 mg/kg/day), all of the tested muscle stretch reflexes except the right knee and the ankle jerks were improved and the H reflex on the left calf muscle was obtained. Latency of this response was normal but amplitude was decreased. The patient's clinical status was also improved. We suggest the basic defect at the neuromuscular junction in this syndrome as the most likely explanation for hypo- and a-reflexia.