Proposed protocol for fasciculations detection by muscle ultrasound in amyotrophic lateral sclerosis

Abstract

Objective: To investigate potential diagnostic value of fasciculations among amyotrophic lateral sclerosis (ALS) patients and determine the most optimal protocol based on selection of a combination of muscles with highest yield in clinical practice.

Methods: The cross-sectional study comprised 149 ALS and 54 non-ALS patients, all underwent muscular ultrasound (MUS) on muscle groups in four body regions to find potential indicators for ALS diagnosis. Fasciculations intensity was divided into five grades based on firing frequency and number in the involved muscle groups. The fasciculations diagnostic score was defined according to the indicators with high specificity for ALS.

Results: Detection rate of fasciculations was highest in the lumbosacral (970/1622, 59.8%) and cervical (841/1516, 55.5%) muscle groups, followed by the thoracic muscles (148/548, 34.3%), and bulbar muscle groups (102/652, 15.6%) among ALS patients (p<0.05). The detection of fasciculations in bulbar and thoracic muscle groups and detection of high-grade fasciculations in cervical and lumbosacral muscle groups were highly specific among ALS patients. Through detailed screening, a total of 13 muscle groups were involved in the fasciculations diagnostic score. Receiver operating characteristic (ROC) analysis showed that the area under curve (AUC) was 0.961 (95%CI 0.927-0.996). The optimal cut-off value was 1 point with 95.8% of sensitivity and 88.9% of specificity.

Conclusions: A practical protocol was feasible with optimal diagnostic yield in suspected ALS to help detect fasciculations. This could complement routine clinical evaluation and electrodiagnostic work-up and be performed as a practical bedside test with little patient burden and low cost.