Electrophysiologic study in benign human botulism type B.

Conventional electromyography (EMG) and single fiber EMG (SFEMG) were performed in a 64-year-old diabetic woman with mild type B botulism. The main clinical signs were autonomic dysfunction and cranial nerves paresis. Conventional EMG was normal, except for small changes that were consistent with mild mixed peripheral neuropathy in the lower limbs and were related to diabetes. Repetitive stimulation and results of single stimulus before and after full effort were normal. SFEMG showed increased jitter and impulse blocking in clinically normal muscles. The jitter was frequency dependent and improved at a higher innervation rate. Impulse blocking in potentials with only slightly increased jitter was found. The follow-up showed improvement of the jitter in agreement with clinical recovery. Jitter abnormalities were recorded after 16 weeks, when clinical signs of botulism had been reversed to normal. Motor unit fiber density increased progressively, and on examination at 8 weeks, some potentials showed very high jitter values. Both findings might suggest new endplate formation, perhaps due to ultraterminal sprouting development.