Muscle Ultrasound Is a Sensitive Outcome Measure in ALS

Area of Science:

• Neurology
• Biomarkers
• Medical Imaging

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease.
• Muscle ultrasound is a developing outcome measure for ALS.
• Prospective, multicenter longitudinal studies are needed to validate its use.

Purpose of the Study:

• To evaluate muscle ultrasound as an outcome measure in ALS.
• To compare the sensitivity of muscle ultrasound with clinical and neurophysiological metrics.

Main Methods:

• Prospective, two-center cohort study of adults with ALS.
• Clinical assessments included ALS Functional Rating Scale-Revised (ALSFRS-R) and MRC sum scores.
• Neurophysiological measures involved median and ulnar nerve compound motor action potential (CMAP) amplitudes.
• Muscle ultrasound of 11 muscles analyzed thickness and echogenicity using harmonized protocols.

Main Results:

• Muscle echogenicity showed the largest effect size (1.09), indicating significant ALS progression.
• ALSFRS-R declined (-0.7%/month, effect size 0.84) and CMAP amplitude decreased (-1.2%/month, effect size 0.77).
• Onset-specific muscle selection, particularly biceps brachii and gastrocnemius, enhanced ultrasound responsiveness (effect sizes 1.12 and 1.18).

Conclusions:

• Muscle ultrasound echogenicity is a sensitive structural biomarker for ALS progression.
• It demonstrates greater responsiveness than ALSFRS-R and CMAP over 3-12 months.
• Its accessibility and sensitivity support its use as an outcome measure in ALS clinical trials.