VerciseTM DBSシステムによるジストニア振戦の早期治療経験

Early Experience with the VerciseTM DBS System in the Treatment of Dystonic Tremor

Ⅰ．はじめに

　脳深部刺激療法（deep brain stimulation：DBS）は，薬剤抵抗性の不随意運動，特にパーキンソン病（Parkinson disease：PD）やジストニア，振戦に対し有効で，確立された治療法である．従来は定電圧刺激のみであったが，2012年から定電流刺激もできるようになり，アドバンスモード，マルチプログラミング（interleaving stimulation），グループ設定などの調節性が向上し，充電式モデルも登場した．Vercise^TM DBS（Boston Scientific Neuromodulation）は，2015年4月に本邦で上市された新しい充電式定電流システムである．Vercise^TM DBSの特徴は，8極リード（Fig.1A）に対し電源供給源がそれぞれ独立していて，各接触子に異なる電流値を1%刻みで配分し，刺激領域をリード軸方向に連続的に移動できる技術を導入している点である（multiple independent current control：MICC）．PDや本態性振戦などに対するDBSに伴う副作用は，マルチプログラミングによるcurrent shapingや，MICCのcurrent steeringを使って刺激の強弱を作ることで回避できる^2,3,4,18)．MICCは本邦ではまだ使用症例が少なく，その繊細な刺激調節性が他機種に比してどのような優位性があるかはわかっていない．今回われわれは，Vercise^TM DBSの発売から1年間に，振戦要素の強いジストニア症例に施行した淡蒼球内節（globus pallidus internus：GPi）に対する電気刺激（GPi-DBS）の早期の使用経験について報告する．

　Six cases of dystonic tremor were treated with the Vercise^TM deep brain stimulation（DBS）system, which has the multiple independent current control（MICC）technology. The mean preoperative score of Burke-Fahn-Marsden dystonia rating scale was 16.2±9.4, which was reduced to 6.1±4.6 at 5 months postoperatively. A 65-year-old male presented an intractable dystonic tremor of the jaw, neck, and shoulders due to tardive syndrome. He experienced the successful tremor relief after unipolar DBS in the globus pallidus internus（GPi）with Vercise^TM but complained of dysarthria. Steering the current ventrally induced nausea without alleviating dysarthria, while steering the current dorsally alleviated dysarthria but a further dorsal current induced mandibular dyskinesia. The current steering with MICC enabled the simulation field in GPi with successful balance, maximizing tremor suppression, and minimizing the adverse effects. In a second case, 61-year-old male in whom cervical dystonia with rotatory tremor had been successfully treated with interleaving stimulation of GPi-DBS had needed to repeat the replacement of a non-rechargeable pulse generator in only 15-month interval. After the substitution of Vercise^TM, the interleaving stimulation of 9.5mA in total was replaced by 8.5mA with the current steering of MICC, while the patient's symptomatic control was unchanged. The microlesion effects after lead implantation are unclear and therapeutic effects are often delayed in cases of dystonia;therefore, the submaximal stimulation intensities must be frequently applied in the early phase following the implantation of DBS. A fine current steering of Vercise^TM DBS is very useful in both, the early and late phases of GPi-DBS for dystonic syndrome.