The effect of transcranial direct current stimulation of pharyngeal motor cortex on swallowing function in patients with chronic dysphagia after stroke: A retrospective cohort study

About 11% to 13% of patients with acute dysphagia induced by stroke remain chronic dysphagia 6 months after stroke which usually leads to many severe complications and poor quality of life. To investigate the effect of transcranial direct current stimulation (tDCS) on swallowing function in the patients with chronic dysphagia after stroke. 26 post-stroke patients with chronic dysphagia who received tDCS were identified by electronic medical records between July 2016 and April 2018. Of which, 13 were treated by unilateral hemispheric anodal tDCS at affected pharyngeal motor cortex. 13 eligible patients only treated by conventional therapies but without tDCS were randomly selected by matching on date of admission (±2 weeks) of the patients receiving unilateral tDCS. The swallowing function and quality of life were evaluated before and 2 weeks after treatment. The patients in three groups were comparable. The swallowing function and quality of life of the patients in all the 3 groups had been improved over time. Comparing to the group without tDCS, both the groups with unilateral or bilateral tDCS had shorter oral transit time (1.69 ± 0.95, 0.97 ± 0.71 seconds, respectively) and higher scores of quality of life (159.76 ± 12.59, 179.69 ± 11.81, respectively) after treatment. Both unilateral and bilateral hemispheric anodal tDCS combined with conventional therapies are helpful for recovery of swallowing function in patients with chronic dysphagia induced by stroke, but bilateral anodal tDCS substantially improve more.