Botulism: electrophysiological studies.

In a patient with botulism type B, electrophysiological studies showed: (1) a pattern in the repetitive nerve stimulation test resembling that found in the Eaton-Lambert syndrome but without any significant increment at high rates of stimulation or posttetanic exhaustion phenomenon; (2) a prominent response to guanidine hydrochloride; (3) a short mean duration of motor unit potentials that reversed with recovery; (4) a mild, prolonged latency and low amplitude of the H-reflex; (5) mild peripheral nerve dysfunction; and (6) a long-lasting persistence of abnormalities beyond the time of clinical recovery. The literature reports two types of responses in the repetitive nerve stimulation test in botulism: in the severe form one obtains a low-amplitude muscle potential, a decremental response at low rates of stimulation, and an insignificant incremental response at high rates of stimulation; in the mild form a normal amplitude of muscle potential occurs together with a normal response to low rates of stimulation and a significant incremental response at high rates of stimulation.