Fasciculation score: a sensitive biomarker in amyotrophic lateral sclerosis

The aim of our study was to elucidate the characteristic of fasciculation distributions in amyotrophic lateral sclerosis (ALS) using a fasciculation score (FS) of muscle ultrasound (MUS) and to compare the diagnostic values of three MUS fasciculation parameters in patients.

Thirty ALS patients, 16 ALS mimics, and 10 healthy subjects were involved. MUS of unilateral 10 muscles in each patient and needle electromyography (EMG) of total 204 muscles were performed to detect fasciculations and spontaneous activity respectively in ALS. Control groups underwent only MUS. Fasciculation was graded semiquantitatively with FS.

Three hundred fifty muscles in ALS and 260 in controls were examined. The fasciculation detection rates, total FS, the number of muscles with fasciculation, and the total number of fasciculations in ALS were all significantly higher than those of controls (P < 0.001). ALS patients exhibited a multifocal continuous pattern of fasciculation in limbs, whereas there were few fasciculations in controls. Compared with other parameters, total FS had the largest area under the curve (AUC) (AUC = 0.899, P < 0.001) in ALS diagnosis. The detection rates of lower motor neuron (LMN) acute lesions by MUS (70.6%) and EMG (72.1%) were nearly the same, and a positive correlation between the FS and spontaneous activity grades (P < 0.001, r = 0.359) was proved.

ALS patients exhibited the multifocal continuous pattern of fasciculation in limbs. FS showed high sensitivity and specificity in differentiating ALS from non-ALS patients, and the optimal cut-off value was determined as 4. The combination of MUS and EMG can provide additional information about specific muscles.