Patients with different myotonic syndromes were evaluated for the presence of transient decrease of muscle fiber excitability. The evoked compound muscle action potential (CMAP) was recorded from the hypothenar eminence; single, supramaximal stimuli were applied to the ulnar nerve at the wrist before and after various periods of voluntary, isometric exercise of the hand muscles. A variable decline of the CMAP after exercise was present in all subjects with myotonia. The results were similar to those obtained with rapid repetitive nerve stimulation.

Five diabetic patients developed upper back or abdominal pain associated with substantial weight loss in three. Electrophysiological evidence of associated thoracoabdominal somatic neuropathy was found in all cases. Signs of a generalized neuropathy were present in two patients, and four had asymmetrical proximal leg weakness. At least two have improved spontaneously. The syndrome is closely related to diabetic amyotrophy; it is probably more common than is recognized.

Sciatic nerve damage by intragluteal injections tends to injure the peroneal nerve trunk more severely than the other components of the sciatic nerve. 2 patients with predominant or sole damage to the posterior tibial nerve trunk were observed. This distribution was documented electrophysiologically. Our cases are unusual and point to a wider spectrum of such injuries. It is also suggested that internal fibrosis of the nerve is of greatest importance as a pathogenetic mechanism in these injuries.

We investigated the diagnostic value of electromyographic (EMG) examination of the anterior abdominal wall muscles (AWMS) in thoracic radiculopathy and compared it with examination of thoracic paraspinal muscles (TPSM). Technically, examination of AWMS was much easier compared to TPSM. In eight patients with thoracic diabetic radiculopathy at the level of T7-T12, AWMS was abnormal in all and was considered to be diagnostic, whereas AWMS was normal in diabetic lumbar radiculopathy, patients with diabetes mellitus without radiculopathy, patients with unspecified gastrointestinal pain, and patients with musculoskeletal-type back pain. We conclude that EMG evaluation for possible thoracic radiculopathy should include examination of AWMS, and if abnormal, would be of great diagnostic help in patients with unspecified gastrointestinal symptoms.

Twenty-five successive patients with myotonic dystrophy were examined to determine the anatomical distribution of electrical myotonia. Proximal and distal limb muscles and orbicularis oris and masseter muscles were examined. Electrical myotonia was present in all muscles examined in only 3 patients. Moreover, of the 15 muscles examined, none showed myotonic discharges in every patient, the highest individual muscle involvement being 96%.