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.

Abbreviations: prob. lab. sup., probable laboratory supported ALS, PMA, progressive muscular atrophy, PNP, polyneuropathy, fasc., fasciculations, MNM, mononeuropathia multiplex, HSP, hereditary spastic paresis, PLS, primary lateral sclerosis, benign cramp fasc., benign cramp fasciculation syndrome, PSP, progressive supranuclear palsy, cerebral vasc., cerebral vascular lesions

Keywords: Amyotrophic lateral sclerosis, Diagnosis, Muscle ultrasound, STARD