Article

Neuromuscular electrical stimulation (NMES) of the muscles underlying
the pharynx and faucial pillars affects the excitability of corticobulbar
projections in a frequency- and duration-specific manner. The anterior
hyomandibular (submental) muscles are primary targets for the clinical
application of NMES to improve disordered swallowing, but the optimal NMES
parameters for this application are unknown. OBJECTIVE: To determine the
influence of NMES parameters on the excitability of corticobulbar projections to
the submental musculature. METHODS: Transcranial magnetic stimulation (TMS) was
used in event-related protocols, triggered by either volitional contraction of
the submental muscles or pharyngeal swallowing, to assess corticobulbar
excitability prior to, immediately following, and 30, 60, and 90 minutes
post-NMES in 25 healthy volunteers. In the first 2 experiments, 4 stimulus
frequencies (5, 20, 40, and 80 Hz) and 3 NMES dosages, manipulated through
stimulus train durations or number of repetitions, were evaluated. The optimal
excitatory NMES triggered by volitional swallowing (event-related NMES) was then
replicated in a new sample and contrasted with non-event-related NMES (either
discrete events or continuously for 1 hour). RESULTS: It was found that 80Hz NMES
increased motor-evoked potential (MEP) amplitude at 30 minutes and 60 minutes
poststimulation only after 60 repetitions of 4-s event-related NMES trains.
Non-event-related and continuous NMES did not affect MEP amplitudes. No changes
in MEP onset latencies were observed. CONCLUSIONS: Changes in corticobulbar
excitability induced by NMES of the submental muscle group are frequency and dose
dependent and only occur after NMES triggered by volitional swallowing.
Underlying neural mechanisms are discussed.

Langue : ANGLAIS