Transcranial Direct Current Stimulation combined with Finger Splinting for Focal Hand Dystonia / The Japanese Journal of Rehabilitation Medicine

ABSTRACT

Patients with focal hand dystonia demonstrate abnormally increased corticospinal excitability, which has been reported to be ameliorated, at least for a short term, with low frequency repetitive transcranial magnetic stimulation (rTMS). Transcranial direct current stimulation (tDCS), which is less costly and easier to apply than rTMS, is also known to modulate cortical excitability. Especially with cathodal tDCS, cortical excitability can be reduced. On the other hand, upper extremity splinting is also known to reduce dystonic symptoms by inhibiting abnormal movement. We therefore combined cathodal tDCS with finger splinting to treat focal hand dystonia in a 34-year-old man with traumatic brain injury who showed involuntary movement of his right fingers during writing and chopsticks use. After 5 days of cathodal tDCS sessions (1mA, 10min), he was encouraged to use interphalangeal joint splints for his thumb and index finger during these activities. We assessed computer-rated handwriting, reciprocal inhibition and intracortical inhibition before, 24 hours and 3 months after the 5-day tDCS sessions. Before the treatment, his flexor pollicis longus (FPL) and first dorsal interosseous (FDI) muscles showed 4Hz rhythmic hyperactivity during writing, and reciprocal inhibition at interstimulus intervals (ISI) of 20 and 100 ms were lost. Paired pulse TMS also revealed disinhibited short interval intracortical inhibition (SICI) at an ISI of 2 and 3 ms. The 5-day tDCS sessions reduced FPL and FDI EMG activities, and SICI and RI at 20 and 100 ms were also restored. Wearing the finger splints, these improvements were maintained at the 3-month follow-up. This case report is the first to demonstrate the possible long-term effects of tDCS combined with splinting for focal hand dystonia. It is supposed that splinting after tDCS plays an important role in making the tDCS aftereffects last longer.