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Session: Motor Control II
Session starts: Friday 25 January, 13:00
Presentation starts: 14:15
Room: Lecture room 558

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Boudewijn Sleutjes (University Medical Centre Rotterdam)
Inger Montfoort ()
Joleen Blok ()

Abstract:
The compound muscle action potential (CMAP) scan is a rapid, non-invasive electrophysiological method from which information on pathologically enlarged motor units (MUs) and/or MU loss can be obtained. The CMAP scan is constructed by plotting recorded CMAP amplitude versus gradually increasing stimulus intensity. The presence of large consecutive differences between successive CMAP amplitudes, also called steps, is indicative of neurogenic disease [1]. Recently, we developed a novel automated method to quantify the CMAP scan pattern in a single parameter, N50. N50 expresses how many of the largest consecutive differences are needed to constitute 50% of the maximum CMAP [2]. The aim of this study is to link N50 to the underlying (patho) physiology by assessing its relation to the number of MUs present. To evaluate this relation, we compared the performance of N50 with that of motor unit number estimates (MUNE) and with a CMAP scan simulation model. Use of a simulation model has as an advantage that it has a known input against with the automated CMAP scan analysis can be compared. Thenar CMAP scans and MUNE were recorded on the same day in 51 Guillain-Barré (GBS) patients and 12 amyotrophic lateral sclerosis (ALS) patients at multiple time points during follow-up. N50 was calculated for the resulting 173 CMAP scans and compared with the MUNE data. In addition, the CMAP scan simulation model was used to generate CMAP scans from which N50 was calculated for each simulated CMAP scan. The number of stimuli was set to 500 and number of MUs was altered from 5 up to 400 MUs. The results show that in the affected muscles N50 and MUNE were highly correlated in conditions of marked MU loss (≤ 80 MUs, r = 0.73, n = 68, p < 0.001). The curve of N50 with simulated number of MUs affirms the trend found in N50 with the MUNE data. We conclude that the automated CMAP scan pattern analysis via novel parameter N50 is a quick and reasonably accurate method to detect MU loss in a range relevant to motor neuron disease. Hence, it may be used to monitor neurogenic disease progression. REFERENCES [1] J.H. Blok, A. Ruitenberg, E.M. Maathuis and G.H. Visser, “The electrophysiological muscle scan”, Muscle & Nerve, Vol. 36, pp. 436 – 446, (2007). [2] B.T.H.M. Sleutjes, I. Montfoort, E.M. Maathuis, J. Drenthen, P. van der Meer, G.H. Visser and J.H. Blok, “Automatic extract of clinical information from the CMAP scan”, 3rd Dutch BME Conference 2011, Jan. 20 - 21, 2011, Egmond aan Zee, The Netherlands