Effects of intermittent theta burst stimulation on cognitive and swallowing function in patients with MCI and dysphagia risk: a randomized controlled trial

Background: Mild cognitive impairment (MCI) is a high-risk factor for dementia and dysphagia; therefore, early intervention is vital. The effectiveness of intermittent theta burst stimulation (iTBS) targeting the right dorsal lateral prefrontal cortex (rDLPFC) remains unclear.

Methods: Thirty-six participants with MCI were randomly allocated to receive real (n = 18) or sham (n = 18) iTBS. Global cognitive function was assessed using the Montreal Cognitive Assessment (MoCA), and executive function was evaluated with the Trail Making Test (TMT), Digital span test (DST) and Stroop color word test (SCWT). Quantitative swallowing measurements were obtained using temporal and kinetic parameters based on the videofluoroscopic swallowing study (VFSS). Resting-state functional magnetic imaging (fMRI) was performed to observe brain plasticity, functional connectivity (FC) values were calculated. All assessments were completed at baseline and two weeks after treatment. Participants received 10 sessions of daily robotic navigated iTBS.

Results: The MoCA score and the SCWT duration of the real group improved significantly compared with that of the sham group. Temporal parameters of VFSS included 5-ml oral transit time (OTT), 5-ml soft palate elevation time (SET) and 10-ml OTT showed a decreasing trend. However, there was significant improvement in 10-ml OTT when choosing patients with OTT exceeding 1000 ms. FC value between the left middle frontal gyrus and the rDLPFC increased significantly in real stimulation group (p < 0.05 with false discovery rate corrected). We found that baseline FC scores were negatively correlated with the SCWT task duration (r = -0.554, p = 0.017) and with the 10-ml OTT (rho = -0.442, p = 0.027) across all participants. Among those in the iTBS group with a pre-10-ml OTT greater than 1000 ms, we observed a positive correlation between changes in MoCA scores and changes in FC values (r = 0.789, p = 0.035). Furthermore, changes in MoCA scores were positively correlated with changes in 10-ml OTT (r = 0.648, p = 0.031), as determined by Pearson analysis.

Conclusions: Navigated iTBS over the rDLPFC has the potential to improve global cognition, response inhibition ability, and certain aspects of swallowing function for patients with MCI at high risk for dysphagia. Changes in FC between right and left DLPFC may underlie the neural mechanisms responsible for the effectiveness of iTBS targeting the right DLPFC.