Objective. To evaluate an automated method that extracts motor unit (MU) information from the CMAP scan, a high-detail stimulus-response curve recorded with surface EMG. Discontinuities in the CMAP scan are hypothesized to result from MU loss and reinnervation. Methods: We introduce the parameter D50 to quantify CMAP scan discontinuities. D50 was compared with a previously developed manual score in 253 CMAP scans and with a simultaneously obtained motor unit number estimate (MUNE) in 173 CMAP scans. The effect of MU loss on D50 was determined with a simulation model. Results: We found a high agreement (sensitivity=86.8%, specificity=96.6%) between D50 and the manual score. D50 and MUNE were significantly correlated below 80 MUs (r=0.65, n=68, p<. 0.001), but not when MUNE was larger than 120 MUs (r=0.23, n=59, p=0.08). Conclusions: Discontinuities in the CMAP scan as expressed by a decreased D50 are related to significant MU loss. The determination of D50 is objective, quantitative, and less time-consuming than both manual scoring and many existing MUNE methods. Significance: D50 is potentially useful to monitor neurogenic disorders and moderate to severe MU loss.

CMAP scan, Motor unit, Neurogenic disorders, Surface EMG
dx.doi.org/10.1016/j.clinph.2013.07.016, hdl.handle.net/1765/63514
Clinical Neurophysiology
Department of Neuroscience

Sleutjes, B.T.H.M, Montfoort, I, Maathuis, E.M, Drenthen, J, van Doorn, P.A, Visser, G.H, & Blok, J.H. (2014). CMAP scan discontinuities: Automated detection and relation to motor unit loss. Clinical Neurophysiology, 125(2), 388–395. doi:10.1016/j.clinph.2013.07.016