Effectiveness of botulinum toxin type A against painful limb myoclonus of spinal cord origin.

Botulinum toxin is now an established treatment for blepharospasm, hemifacial spasm, spasmodic torticollis, and spastic dysphonia. We report the effectiveness of botulinum toxin against painful limb myoclonus of spinal cord origin. The patient, a 16-year-old girl with a pulmonary vascular anomaly, Scimitar syndrome, suffered from an acute spinal cord infarct at age 11. She was left with paralysis of the right leg and bladder dysfunction. Four years after the original insult, she developed "painful cramping" and involuntary movements of the left thigh, which were unresponsive to a wide range of therapeutic trials. The movements were continuous, rhythmic, and confined to the left quadriceps muscles. Electromyographic examination revealed continuous myoclonic discharges. Treatment with botulinum toxin in the left quadriceps muscles resulted in complete cessation of pain and marked reduction in amplitude of the movements, both clinically and electromyographically. This observation indicates the efficacy of botulinum toxin in the treatment of painful spinal myoclonus.