Introduction Recovery of swallowing function in unilateral dysphagic stroke patients is associated with increased pharyngeal motor cortex excitability of the unlesioned hemisphere. “Virtual-lesioning” the human pharyngeal motor cortex transiently disrupts swallowing neurophysiological and behavioural function for up to 45 min. During this window of opportunity we trialled the effects of contralesional tDCS, a novel non-invasive brain stimulation technology, on “virtual-lesion” induced brain and behavioural changes to swallowing function.
Methods In 15 healthy volunteers (eight males, 21–61 years old) hemispheric lateralisation and cortical excitability of pharyngeal and hand motor cortex were mapped using Transcranial Magnetic Stimulation via an intraluminal catheter with electromyography and pressure sensors. Volunteers then received a “virtual-lesion” to the strongest pharyngeal projection and were randomised to either 10 min of 1.5mA Anodal tDCS (Active) or Sham to the unlesioned hemisphere on separate days. In Experiment 1, effects of tDCS on cortical excitability were compared to baseline over 60 min. In Experiment 2, swallowing behavioural measurements using a swallowing reaction time task were used to calculate a time window for challenge swallows. Swallowing behaviour was assessed for 60 min after tDCS and compared to baseline. Data were compared using repeated measures ANOVA.
Results Experiment 1; compared to sham, active tDCS abolished the inhibitory effects of the “virtual-lesion” bilaterally (p=0.017) with a maximum increase in excitability from baseline of 34% in the un-lesioned hemisphere (Abstract OC-092 figure 1). No significant changes were observed in the hand. Experiment 2; compared to sham, active tDCS significantly improved challenge swallow performance (p=0.025) with a maximal improvement of 174%.
Conclusion Contralesional tDCS reverses the neurophysiological and behavioural consequences of a “virtual-lesion” in healthy individuals and has therapeutic potential for dysphagia rehabilitation.
Competing interests None declared.
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