パーキンソン病に伴う脊椎変性疾患の治療

Management of Spinal Disorders in Parkinson's Disease

Ⅰ はじめに

　パーキンソン病（Parkinson's disease：PD）は，かつて「発症後10年で寝たきりになる」と言われ，実際，L-ドパが使われる以前には発症後の平均生存期間は9.4年であり，死亡率も非PD群の約3倍であると報告された^1）．しかし，1970年代に治療薬としてL-ドパが普及し，その後，PD治療はめざましく進歩した．1986年以降の信憑性の高い発端コホート研究^2）に限れば，PDの死亡率は非PD群の約1.5倍という報告が多数である．

　発症後の生命予後が延長した一方で，PDの長期罹患に伴う合併症にどう対処するか，つまり，機能予後をいかに改善するかが新たな課題になっており，その1つが脊椎変性である．その背景には，PDの有無にかかわらず加齢性疾患を発症するということだけではなく，PD症状としての傍脊柱筋の筋緊張異常や姿勢保持障害によって，PDでは非PDとは異なる生体力学的・生理学的作用が脊椎に働いていることがあると考えられる．

　本稿では，PD患者の脊椎変性の特徴を概説し，脊椎外科の観点からみた治療の可能性と限界を考える．

　Parkinson's disease（PD）is a degenerative disorder of the central nervous system. Its cardinal features are resting tremor, rigidity, bradykinesia, and postural instability. Several years after disease onset, many patients with PD exhibit postural deformities, including camptocormia, Pisa syndrome, and dropped head syndrome, which can lead to spinal deformities. In addition, spinal degenerative disorders are frequently associated with PD and can further impact the patients' quality of life. Current evidence suggests a multifactorial etiology for postural deformities and spinal degenerative disorders in PD, which includes abnormal stress on the spine（biomechanical factors）, postural instability and impairment of postural compensation（physiological factors）, and imbalance of dopaminergic signals（pharmacological factors）. The relative contribution of these factors varies between patients and across symptoms. Consequently, neurologists have difficulty treating these axial problems. Moreover, many studies have reported poor outcomes and high complication rates of spinal surgery in patients with PD, which embarrasses spinal surgeons.

　An improved understanding of the mechanisms underlying spinal problems in PD might ultimately lead to more effective management of these disabling complications.