孤発性脊髄小脳変性症の分類を再考する

The Nomenclature and Classification of Sporadic Spinocerebellar Degeneration

脊髄小脳変性症は，既知の原因による二次性のものを除いた小脳性運動失調を主症状とする疾患の総称である。遺伝性と孤発性に大別され，いずれも純粋小脳型と多系統障害型に分類される。しかし，国際的に統一された分類法が存在しないため，特に孤発性脊髄小脳変性症において本邦と諸外国で用いられている疾患名の指す概念に相違が生じている。本稿では疾患概念の変遷を概説し，孤発性脊髄小脳変性症の分類と疾患名を再考する。

Abstract

Spinocerebellar degeneration (SCD) is a neurodegenerative disease characterized by progressive cerebellar ataxia. SCD has a wide range of clinical, pathological, and genetic features, including whether the disease is sporadic or hereditary, and whether it manifests as purely cerebellar or affects multiple systems. Therefore, the classification of SCD has been complicated and has changed over time. Recent advances in genetic testing have shed light on the classification of hereditary SCD. In contrast, the classification of sporadic SCD remains chaotic and there exist nomenclature discrepancies in sporadic SCD between Japanese and English literature. Sporadic SCD is usually divided into multiple system atrophy and cortical cerebellar atrophy in Japanese literature, but the latter nomenclature seems to be uncommon in English literature. The aim of this review is to reconsider the nomenclature and classification of sporadic SCD. At this time, sporadic adult-onset ataxia of unknown etiology is an acceptable term to describe a case of sporadic SCD that does not fit the multiple system atrophy classification.