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

Rationale: 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.

Patient Concerns: 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.

Diagnoses: In needle electromyography, abnormal dystonic patterns were observed in the left abductor hallucis (AH), flexor hallucis longus, and flexor hallucis brevis muscles.

Interventions And Outcomes: These symptoms resolved with a single BTX-A injection to the AH muscle.

Lessons: In this case, a single BTX-A injection to 1 muscle for treating progressive focal dystonia was effective on a distant noninjected muscle.