O124 Excitability tests with high-density surface-EMG: A novel approach to study single motor axons

• Published in: Clinical neurophysiology Vol. 128; no. 9; pp. e218 - e219
• Main Authors: Sleutjes, Boudewijn, Boskovic, Ernest, Van Schelven, Leonard, Drenthen, Judith, Kovalchuk, Maria, Lumens, Paul, den Berg, Leonard Van, Franssen, Hessel
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2017
• Subjects: Excitability testing; High-density surface-EMG; Motor unit action potentials; Single human motor axons; Excitability testing; High-density surface-EMG; Single human motor axons; Motor unit action potentials
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2017.07.135

To study excitability in single motor axons by using high-density surface-EMG. Motor unit action potentials (MUAPs) were evoked by submaximal stimulation of the median nerve at the wrist and recorded with a 9×14 surface electrode array on the thenar muscles. For excitability testing, the most specific single-channel surface-EMG signal was selected by its spatiotemporal profile. Excitability tests were successfully performed in 10 single motor axons of seven healthy subjects. The mean absolute threshold of the single MUAPs was (5–95th percentile, 1.5–8.5mA, n=10), which showed to be stable throughout the recordings. Selecting an optimal signal-channel surface-EMG mitigated interference of other MUAPs and improved signal-to-noise ratio. Excitability recordings from single axons may reveal abnormalities that are masked in recordings of compound potentials. However, current methods have limitations in reliably detecting MUAPs for the purpose of deriving excitability-variables from single axons, except in conditions with marked axon loss. Using our novel approach we have partly overcome this issue, since high-density surface-EMG aids in the identification of single MUAPs, which facilitates the application of excitability tests on single motor axons. High-density surface-EMG is suitable to reliably assess excitability in up to three axons per nerve. Our method makes it possible to assess ion-channel dysfunction in single motor axons in nerves without prominent axon loss.