[A case of myokymia with abnormal F responses].

We reported a case of myokymia with abnormal F response. A 60-year-old male with chronic alcoholism was admitted to our hospital with complaint of muscle cramp in both legs just after drinking. Neurological examination revealed muscle pain and weakness of the legs, absence of bilateral Achilles tendon reflexes and prominent myokymia in his right quadriceps femoris and left calf muscles. The electrophysiological examination showed reduced conduction velocity, high amplitude, increased number of phases and long duration of F responses suggesting increased excitability of motoneuron pool. The epidural nerve block brought about a disappearance of the myokymia and an improvement of the abnormal features of F response. The myokymia gradually tended to be milder in the clinical course. The relationship between the myokymia and the abnormal F responses indicated that the increased excitability of spinal motoneurons might play an important role on the generation of myokymia of this patient.