上肢局所性ジストニアに対する経頭蓋直流電気刺激（transcranial direct current stimulation：tDCS）と指節関節固定スプリント併用の試み

Transcranial Direct Current Stimulation combined with Finger Splinting for Focal Hand Dystonia

要旨：上肢局所性ジストニア患者においては，大脳皮質興奮性の増大が認められ，皮質興奮性を低下させる低頻度反復経頭蓋磁気刺激（rTMS）が，症状の改善に有効であることが知られている．より簡便な経頭蓋直流電流刺激（tDCS）も皮質興奮性の修飾をもたらすことが報告されており，局所性ジストニアの治療に有効な可能性がある．さらに装具を用いた上肢運動の抑制により，局所性ジストニアが軽減することも報告されている．そこで，われわれは，上肢局所性ジストニアに対して，tDCSと装具の併用療法を施行した．Cathodal tDCSは刺激強度1mA，刺激持続時間10分間，1日1回，5日間連続して施行し，その後，右母指と右示指の指節関節固定装具を装着させた．5日間連続のtDCSの後には，書字動作時の長母指屈筋と第一背側骨間筋の過剰な筋活動が減少し，刺激間隔20ms，100msにおける相反性抑制ならびに皮質内抑制の出現を認めた．さらにスプリントの装着により，その効果は3カ月後にも維持されていた．tDCSとスプリントの併用療法は，局所性ジストニアの治療に有効である可能性が示唆された．

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.