脳・神経刺激療法のtranslational research

Translational Research for Neurostimulation

Ⅰ．はじめに

　脳神経外科の様々な領域は，大まかには臨床の場で培われた経験に基づく知見と論理的な方法論に基づく研究の成果の2つを基盤に発展してきたといえよう．その中でも脳・神経刺激療法を中心とした定位・機能神経外科という領域は，研究が寄与する部分の特に多い分野の1つといえる．既に，脳・神経刺激療法は脳神経外科医療の中で1つの分野として確立しているが，これまでの長い歴史の中で数多くの基礎あるいは臨床研究の成果を基盤として発展してきた．そして，これからの発展もこうした研究成果なしにはあり得ないであろう．事実，この領域は，近年の電子工学技術の進歩に伴い，さらなる大きな発展が期待されている．本稿では，定位・機能神経外科領域の基盤となった主たる研究の流れを初めに概観する．さらに，神経刺激の作用機序の解明，新たな刺激部位や適応疾患拡大のための基礎ならびに臨床研究について記載し，最後に今後の展望について述べる．

　The effects of electrical stimulation on the nervous system have been known for many years. Electrical stimulation has been employed as a treatment of functional diseases of the nervous system and has been mainly developed on the basis of deep brain stimulation (DBS), motor cortex stimulation (MCS), and spinal cord stimulation (SCS). Over the past two decades, DBS has replaced lesioning techniques as a treatment for movement disorders, and DBS has been shown to be safe and efficacious. The field of application for DBS is becoming wider, currently encompassing dystonias, epilepsy, and psychiatric disease. On the other hand, MCS has been employed as a therapy for intractable pain for more than ten years. Recently, this therapy has been used as a treatment for involuntary movements and motor palsy caused by stroke. Although the effects of electrical stimulation are distinct and the therapeutic benefits are well recognized, the exact mechanisms of these therapies have not yet been fully clarified. Animal experiments, either in vitro or in vivo, show complex patterns roughly suggesting inhibitory effects. More recent data from in vitro biological research studies show that electrical stimulation affects cellular functions, particularly protein synthesis, suggesting that it could alter synaptic transmission and reorganize neural networks. Research for the understanding of the effects of electrical stimulation at the neuronal level is still in progress, and knowledge from these research will eventually improve the effectiveness of this therapy. Moreover, these basic research and preliminary clinical studies will call for the re-examination of the basic effects of electricity on living tissues because it is now clear that electrical stimulation has a wider application. In this review, we summarizes the history and rationale behind electrical neurostimulation therapy and the recent applications of this technique for various functional diseases of the nervous system.