Differentiation Between Amyotrophic Lateral Sclerosis and Mimics: Quantitative Analysis of Fsciculation with Muscle Ultrasonography

Objective To determine the diagnostic accuracy of the intensity of fasciculation evaluated by muscle ultrasonography in the differential diagnosis of amyotrophic lateral sclerosis (ALS). Methods We prospectively ALS patients who were recruited by Peking Union Medical College Hospital from 2017 to 2020. 61 neuropathy-radiculopathy patients were recruited and 22 health controls as the control. The Medical Research Council (MRC) scale to evaluate the muscle strength. Maximal grade of fasciculations, total fasciculation score, and fasciculation grade were assessed in 16 muscle groups of patients at the first visit using ultrasonography. A receiver operating characteristic curve and the area under the curve were used to calculate the sensitivity and specificity of maximal grade of fasciculations, total fasciculation score, and fasciculation grade in differentiating between ALS and ALS mimics. Spearman correlation analysis was used to analyse the correlation of fasciculation grade with disease duration, ALSFRS score, total MRC score of all limb muscles, MRC score of the muscle, age of onset, and region of onset. Results The maximal fasciculation grade of limb muscles of 84.9% ALS patients and 9.8% neuropathy-radiculopathy patients was higher than grade 2 (χ2 = 101.3, P < 0.01). The total fasciculation score of the 16 limb muscles was 29 (15, 41) in ALS patients and 3 (0, 8) in neuropathy-radiculopathy patients [median (P25, P75)] respectively. Remarkable fasciculations were seen in muscles with a Medical Research Council (MRC) scale between 2 and 4, followed by MRC score 5, and then in those with MRC score 0 and 1. For the total fasciculation score, the sensitivity and specificity for the diagnosis of ALS were 80.6% and 93.4% (cut-off value 14). When the Medical Research Council was 4 and 5, respectively, 42.3% and 24.1% of muscles showed fasciculation grade ≥ 3 in ALS, while only 1.7% and 0 neuropathy-radiculopathy patients showed fasciculation grade ≥ 3. Conclusion A combined analysis of fasciculation intensity and MRC score of the limb muscles may be helpful for differential diagnosis of ALS.