Propriospinal myoclonus in tetraplegic patients: clinical, electrophysiological and therapeutic aspects

Propriospinal myoclonus is a rare and relatively little studied complication of spinal cord injury. We report two patients with an extension-producing myoclonus presenting with tetraplegia caused by cervical trauma. Rhythmic extension jerks of the trunk and lower limbs appeared several weeks after their injury in a context of severe spasticity. The characteristics of these jerks were determined by polymyography of 12 muscles. They lasted between 306 and 1127 ms with a frequency of 0.3 to 0.5 Hz. By comparing latencies their origin was found to be in the lumbar cord from which there was a slow (2 m s-1) upward and downward spread. Oral treatment with baclofen and sodium valproate was partially successful in one patient, but ineffective in the other. Intrathecal 75 or 100 micrograms baclofen produced a striking, complete disappearance of myoclonus prompting the implantation and successful use of a baclofen pump in one patient. These two new cases suggest the existence of a lumbar generator in which myoclonic extension jerks originate, and demonstrate a new therapeutic alternative in intrathecal baclofen for patients resistant to oral medication.