Introduction There is good evidence for a role of the cerebellum in swallowing physiology and we have previously shown that longer-lasting changes of human pharyngeal motor cortex can be induced by 10 Hz repetitive transcranial magnetic stimulation (rTMS) applied to the cerebellum. This study aimed to examine the therapeutic potential and cerebellar hemispheric specificity of 10 Hz cerebellar rTMS by testing its ability to reverse focal cortical suppression induced by a virtual lesion over the (dominant) pharyngeal motor cortex in healthy humans.
Method Fifteen healthy volunteers (7 males, age range 19–49 years) participated and were intubated with an intraluminal catheter for recording pharyngeal electromyography (EMG). Baseline measurements of cortical excitability assessed through motor evoked potentials (MEP) at three sites (both dominant and non-dominant pharyngeal cortices and hand motor cortex) and cerebellar excitability in each cerebellar hemisphere were obtained by single-pulse TMS. Thereafter, each subject received 1 Hz rTMS (for 10 min at an intensity of 120% of resting motor threshold) to dominant pharyngeal motor cortex to transiently suppress cortical swallowing activity. Subsequently, subjects were randomised to receive one of three cerebellar 10 Hz rTMS interventions (ipsilesional cerebellar hemisphere, contralesional cerebellar hemisphere and ipsilesional sham). Post-intervention, cortical (pharynx and hand) and cerebellar MEPs were re-measured for up to 60 min and compared to sham using repeated measures and one way ANOVA.
Results As there was no difference in the pattern of excitability between each cortical hemisphere, pharyngeal hot spots were combined and compared to sham using repeated measures ANOVA. Post hoc 1-way ANOVAs comparing each treatment to sham confirmed that rTMS to either cerebellar hemispheres significantly increased cortical excitability, which lasted up to 60 min ( p<0.05) and completely reversed the focal suppression induced by the virtual lesion. While there were no statistical hemispheric differences, contralesional cerebellar stimulation appeared to show visibly greater effects. By contrast, there were no effects directly seen on cerebellar excitability.
Conclusion Ten Hz rTMS to either cerebellar hemisphere was able to reverse the inhibition provoked in pharyngeal motor cortex after a virtual lesion. Our data suggest that 10 Hz cerebellar rTMS may have a therapeutic role in recovery from dysphagia following brain injury, with the suggestion that stimulation to the contralesional cerebellum might have more sustained effects.
Disclosure of Interest None Declared
- pharyngeal motor cortex