Treatment of focal dystonia involving multiple muscles with a single injection of botulinum toxin A to 1 muscle: A case report

Botulinum toxin A (BTX-A) injection is effective in treating focal dystonia. However, there are no prior reports regarding the treatment of progressive focal dystonia by a single BTX-A injection that affect a distant muscle. A 19-year-old male was referred to the rehabilitation clinic with a complaint of involuntary movement in his left big toe. The involuntary movement pattern was initially observed in the abduction direction only; however, it progressed to irregular mixed patterns in the flexion and abduction directions. In needle electromyography, abnormal dystonic patterns were observed in the left abductor hallucis (AH), flexor hallucis longus, and flexor hallucis brevis muscles. These symptoms resolved with a single BTX-A injection to the AH muscle. In this case, a single BTX-A injection to 1 muscle for treating progressive focal dystonia was effective on a distant noninjected muscle.