Multiple Point Stimulation MUNE in ALS: Toward a Faster Modification.

Abstract

Multiple point stimulation is a well-established motor unit number estimate method that can be used in all EMG machines, but it is time-consuming. We investigated whether a faster modification of multiple point stimulation using five surface motor unit action potentials (sMUAP) had similar reproducibility, sensitivity, and specificity as 10. Twenty-two motor neuron disease patients and 20 healthy controls were prospectively examined by two physicians twice in the thenar muscles. A total of 168 multiple point stimulation motor unit number estimate recordings were obtained. Mean motor unit number estimate was significantly lower in patients in contrast to the controls, whether using 5 (53 ± 55 [1-170] vs. 150 ± 64 (51-325), P < 0.001] or 10 sMUAP [52 ± 51 (1-162) vs. 151 ± 50 (75-274), P < 0.001]. No significant differences (P > 0.05) were found between mean motor unit number estimate obtained from 5 or 10 sMUAP in both patients and controls. Intra-rater coefficient of variation (CV) for patients (17% vs. 15%) and controls (16% vs. 13%) and inter-rater coefficient of variation for patients (25% vs. 24%) did not differ between five and 10 sMUAP (P > 0.05), whereas interrater coefficient of variation was higher for five sMUAP in controls (21% vs. 16%, P = 0.004). An excellent intraclass correlation coefficient (≥0.78) was found, sampling either 5 or 10 sMUAP, for both groups. Receiver operating characteristic curves collecting 5 or 10 sMUAP showed excellent accuracy in distinguishing between patients and controls. The faster modification of Multiple point stimulation by sampling five sMUAP had similar reproducibility, sensitivity, and specificity as 10 and may be suggested in future research and clinical practice.