[Clinical analysis of the complex repetitive discharge following M wave]

In the nerve conduction study (NCS), the complex repetitive discharge (CRD) which follows M wave is occasionally observed. To understand the origin of CRD, we clinically analyzed the cases with CRD. Among the 1,580 cases examined by NCS, 13 (0.82%) cases including 6 of myotonic dystrophies (MyD), 2 of carpal tunnel syndrome and a case of multiple sclerosis, chronic inflammatory demyelinating polyradiculoneuropathy, compression fracture of a lumbar vertebra, myasthenia gravis (MG) or Isaacs' syndrome had CRD. CRD was divided into forms; one consisted of an attenuating train of the complex of muscle potentials (muscular form) and the other one formed a simple repetition of single motor unit action potential (neural form). MyD, MG, and Isaacs' syndrome showed muscular form, and the others neural form. The pathophysiology of CRD was considered from the sites of lesions of nerve terminals, neuromuscular junctions, or muscle fibers and that the neural form might result from the axonal regeneration of peripheral motor nerve fibers.