Researchers assessed the accuracy of 3 different methods to detect muscle fasciculations in spinal muscular atrophy (SMA) and found muscle ultrasound (MUS) to have the greatest accuracy in distinguishing SMA from other genetic muscle diseases, as published in Neuromuscular Disorders.

They employed physical examination, MUS, and electromyography (EMG) to detect muscular fasciculations.

“This study aimed to evaluate the diagnostic properties of the detection of muscle fasciculations for SMA diagnosis in adolescents and adults with proximal muscle weakness,” the authors wrote. “Muscle ultrasound presented the best diagnostic accuracy and physical examination combined with MUS seemed to be a good strategy for screening adolescents and adults with proximal muscle weakness for SMA.”

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The research team conducted exploratory diagnostic accuracy cross-sectional study between October 2019 and February 2021 at a single center in Brazil. The 19 participants had a genetic or pathological neuromuscular disorder including proximal or symmetrical muscle weakness. They were divided into 2 groups: later-onset SMA (n=10) and genetic muscle disease (n=9) with proximal weakness.

The results showed that all of the patients with SMA presented fasciculations on MUS, with moderate specificity when assessing any of the 6 studied muscle groups for fasciculations. The reliability of MUS between operators was good to excellent, compared with physical examination, which had only moderate inter-rater reliability.

The authors note that 42% of the participants did not agree to undergo EMG, and therefore no solid conclusions about that method can be made. Furthermore, the small sample size and its exploratory design limit the ability to draw firm conclusions.

The authors recommend further studies with larger samples and an assessment of the 3 methods of fasciculation detection prior to diagnostic confirmation in a prospective design to better validate the usefulness of these methods in later-onset SMA.


Rocha dos Santos MA, Brighente SF, Massignan A, et al. Accuracy of muscle fasciculations for the diagnosis of later-onset spinal muscle atrophy. Neuromuscul Disord. Published online July 14, 2022. doi:10.1016/j.nmd.2022.07.395