Muscle ultrasonography: a diagnostic tool for amyotrophic lateral sclerosis

Abstract

Objective: In a prospective study we tested whether muscle ultrasonography can differentiate between amyotrophic lateral sclerosis (ALS) and mimics. Furthermore, we assessed the ability of ultrasonography to identify subclinical lower motor neuron involvement.

Methods: In 59 patients, suspected for adult onset motor neuron disease, ultrasound scans were made of 12 different muscle groups. Echo intensity was determined and each muscle was screened for fasciculations. Ultrasonography was considered diagnostic for ALS when echo intensity was 1.5 SD above normal in at least two muscles and fasciculations were present in at least four muscles.

Results: Ultrasonography differentiated between ALS and mimics with 96% sensitivity and 84% specificity. In the 27 ALS patients, ultrasonography detected 15 regions with lower motor neuron involvement that were negative using either clinical examination or needle EMG.

Conclusions: Muscle ultrasound can differentiate between amyotrophic lateral sclerosis and mimics with high sensitivity and specificity, and is a sensitive tool to screen for regional lower motor neuron involvement.

Significance: Muscle ultrasonography is a promising tool in the diagnostic work up of ALS.