AUTHOR=Semeia Lorenzo , Middelmann Thomas , Baek Sangyeob , Sometti Davide , Chen Hui , Grimm Alexander , Lerche Holger , Martin Pascal , Kronlage Cornelius , Braun Christoph , Broser Philip , Siegel Markus , Breu Maria-Sophie , Marquetand Justus 

TITLE=Optically pumped magnetometers detect altered maximal muscle activity in neuromuscular disease

JOURNAL=Frontiers in Neuroscience

VOLUME=Volume 16 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2022.1010242

DOI=10.3389/fnins.2022.1010242

ISSN=1662-453X

ABSTRACT=Optically pumped magnetometers (OPM) are quantum sensors that enable the contactless, non-invasive measurement of biomagnetic muscle signals, i.e., magnetomyography (MMG). Due to the contactless recording, OPM-MMG might be preferable to standard Electromyography (EMG) for patients with neu-romuscular diseases, in particular when repetitive recordings for diagnostic and therapeutic monitoring are mandatory. OPM-MMG studies have been focusing on recording physiological muscle activity in healthy individuals, whereas research in neuromuscular patients with pathological altered muscle activity is non-existent. 
Here, we report the application of OPM-MMG in patients with neurogenic muscle damage. Specifically, we compare the muscular activity during maximal isometric contraction of the left rectus femoris muscle in three neuromuscular patients with severe (TTR amyloidosis in combination with Pompe´s disease), mild (Charcot-Marie-Tooth disease type 2), and without neurogenic damage (Myotonia Congenita). Seven healthy young participants served as control group. As expected, and confirmed by using simultaneous surface electromyography (sEMG), a time-series analysis already revealed a dispersed interference pattern during maximal contraction with high amplitudes. Furthermore, both patients with neurogenic damage showed a reduced variability of the MMG-signal, quantified as signal standard deviation of the main component of the frequency spectrum, highlighting the reduced possibility of motor unit recruitment due to the loss of motor neurons. Our results show that recording pathologically altered voluntary muscle activity with OPM-MMG is possible, paving the way for the potential use of OPM-MMG in larger studies to explore the potential benefit in clinical neurophysiology.