ALSの超音波診断

Utility of Muscle Ultrasonography for the Diagnosis of Amyotrophic Lateral Sclerosis

神経筋疾患の診断に，超音波検査が一般的に利用されるようになりつつある。筋萎縮性側索硬化症（ALS）の診断においても，超音波検査の応用が始まっている。ALS診断で試用されている超音波の検査項目には，エコー輝度，筋の厚さ，線維束性収縮がある。現時点では手技の標準化，一般化はまだ十分とはいえない。しかし，ALSで特徴的である線維束性収縮は非侵襲的かつ容易な手技で明確に描出でき，診断に貢献できる可能性がある。ALSでは確定診断に至るまで，筋電図検査が繰り返し行われることが多い。今後，痛みのないALS診断への超音波検査の貢献が期待される。

Abstract

The diagnosis of amyotrophic lateral sclerosis (ALS) is frequently challenging, because motor neuron involvement is usually focal at disease onset and many syndromes mimic ALS. Neurological examination and needle EMG are important in the diagnosis of ALS, and patients with early-stage ALS usually undergo several EMG examinations before the diagnosis is confirmed. Ultrasonography has recently been used for the non-invasive assessment of neuromuscular disorders. This review discusses the recent advances in ultrasonography for ALS diagnosis.

Ultrasonography could help detect lower motor neuron involvement by evaluating muscle volume, echo intensity, and fasciculations. Previous reports have documented the diagnostic values of all these parameters. In particular, fasciculations are characteristic features of ALS that can be easily and reliably visualized using ultrasonography. Moreover, the combined use of ultrasonography and EMG to detect fasciculations could substantially increase the diagnostic sensitivity of Awaji criteria for ALS.

Attempts to utilize ultrasonography for ALS diagnosis have started only recently, and the technique used is yet to be standardized. However, ultrasonography has a major advantage over EMG in that it is non-invasive. Further studies are needed to understand the use of ultrasound as a novel non-invasive tool for ALS diagnosis.