シャルコー・マリー・トゥース病の超音波診断

Ultrasound Diagnosis of Charcot-Marie-Tooth Disease

近年，高解像度プローブの開発により神経や筋の詳細な超音波イメージングが可能となった。これを受けて，超音波検査は，神経内科領域でも，末梢神経疾患の診断の補助として，欧米を中心に広く用いられるようになってきている。本稿では，神経根の観察も含めた末梢神経の超音波検査の基本的な実施方法を述べるとともに，シャルコー・マリー・トゥース病患者の，遺伝子異常で分類したサブタイプごとの神経超音波検査所見について概説する。

Abstract

Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous group of diseases with over 45 different causative gene mutations identified. Nerve conduction studies are important for the classification and diagnosis of CMT, whereas ultrasound (US) is increasingly used to assess the peripheral nerves of patients with CMT, as a complement to neurophysiological studies. Recent ultrasound assessment reports of peripheral nerves in CMT are summarized here. An ultrasound finding of CMT1A, which is the most common demyelinating subtype of CMT, is characterized by uniform enlargement of peripheral nerves and nerve roots. Patients with CMT1B (MPZ mutation) also have larger nerves than normal subjects do. Peripheral nerves of patients with CMT2, which is an axonal type of CMT, are slightly larger than those of normal subjects. Focal enlargement of nerves at entrapment sites is a characteristic US finding of hereditary neuropathy with liability to pressure palsy. US findings of CMT are thus subtype-specific. Therefore, the assessment of nerve US may become a useful supporting tool for the diagnosis of CMT subtypes.