Three-dimensional amplitude characteristics of masseter motor units and representativeness of extracted motor unit samples. Issue 3 (March 2019)

• Record Type: Journal Article
• Authors: Lapatki, Bernd Georg; Eiglsperger, Ulrike; Schindler, Hans Jürgen; Radeke, Johanna; Holobar, Ales; van Dijk, Johannes Petrus
• Is Part Of: Clinical neurophysiology. Volume 130:Issue 3(2019:Mar.)
• Page Start: 388
• Page End: 395
• Publication Date: 2019-03
• Subjects: TMD temporomandibular disorder -- MU motor unit -- HDsEMG high-density surface electromyography -- PNR pulse-to-noise ratio -- MUAP motor unit action potential; Masseter -- Electromyography -- High-density surface EMG -- Scanning EMG -- Motor unit -- Temporomandibular disorder; Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2018.12.008
• Languages: English
• ISSNs: 1388-2457

Abstract

Highlights: High-density surface electromyography (HDsEMG) detects small and large motor units (MUs) located in the outer 70% of the masseter's cross-section. HDsEMG detects MUs from the entire muscle surface in one measurement. From a 3D point of view, HDsEMG detects the most representative MU sample. Abstract: Objective: This study aimed to characterize amplitude topographies for masseter motor units (MUs) three-dimensionally, and to assess whether high-density surface electromyography (HDsEMG) is able to detect MU samples that represent the masseter's entire MU pool. Methods: Ten healthy adult volunteers participated in the study, which combined three EMG techniques. A HDsEMG grid covering the entire masseter, and intramuscular fine-wire electrodes were used to obtain two independent MU samples for comparison. The MUs' amplitude profiles in the dimension of muscle depth were determined using scanning EMG. All data were recorded simultaneously during a low, constant contraction level controlled by 3D force feedback. Results: The median medio-lateral diameter of 4.4 mm (range: 1.2–7.9 mm) for MUs detected by HDsEMG did not differ significantly (Mann-Whitney-U test, p = 0.805) from that of 3.9 mm (0.6–8.6 mm) for MUs detected by fine-wire EMG. For individual subjects, the medio-lateral diameters of all HDsEMG-detected MUs spanned 70.5% (19.2–75.1%) of the masseter's thickness. Conclusions: HDsEMG is able to examine small and large MUs from a great masseter proportion in one single measurement. Significance: Clinical application of HDsEMG might contribute to a better understanding of neuromuscular adaptations in patients with temporomandibular disorders (TMD) and could allow for monitoring treatment effects.