Genioglossus was stimulated intramuscularly to determine the effect of regional activation of the muscle on tongue movement in eight healthy adults. Stimulation at motor threshold was delivered with a needle electrode inserted to different depths in the anterior and posterior regions of genioglossus. The current amplitude that induced muscle contraction was ∼80% higher for anterior than posterior sites. Evoked tongue movements were determined from stimulus-triggered averages (150 pulses) of the outputs from an accelerometer fixed to the posterosuperior surface of the tongue. The median amplitude [95% confidence intervals] for the resultant acceleration was 0.0 m/s2 [0.0, 0.2] for anterior and 0.6 m/s2 [0.1, 2.8] for posterior sites. There was a positive relationship between acceleration amplitude and stimulation depth in the posterior of genioglossus (p < 0.001), but acceleration amplitude did not vary with stimulation depth in the anterior region (p = 0.83). This heterogeneity in acceleration responses between muscle regions may contribute to differences in collapsibility of the upper airway.
- Upper airway