Tongue Surface Electromyography Detects Reduced Motor Unit Recruitment in Oropharyngeal Cancer Survivors With Hypoglossal Neuropathy

This proof-of-concept case-control study examined the feasibility of tongue high-density surface electromyography (HDS-EMG) to detect hypoglossal neuropathy. We analyzed tongue HDS-EMG for N = 2 participants. Subjects were graded through clinical tongue functional measures and gold-standard needle EMG. We collected HDS-EMG in three tongue tasks: relaxation, protrusion, and isometric maximum effort. The HDS-EMG was decomposed into motor unit spike train estimates. Muscle relaxation HDS-EMG contained spikes consistent with fasciculation potential morphology. During tongue protrusion, a case of confirmed CN XII neuropathy exhibited an elevated motor unit (MU) discharge rate and fewer MUs (45.71 peaks/s, 3 estimated MUs) compared to the control (11.63 peaks/s, 11 estimated MUs). During isometric contraction, the case exhibited an average discharge rate of 3.96 peaks/s on 3 MU estimates, whereas the control had a discharge rate of 2.58 peaks/s on 5 MU estimates. Non-invasive tongue HDS-EMG appears to show potential sensitivity for detecting reduced MU recruitment in hypoglossal neuropathy.