This group will include 19 patients. The patients in this group will receive 20 minutes of tDCS over the bilateral cerebellar hemispheres.

This group will include 19 patients. The patients in this group will receive 20 minutes of tDCS targeting the cortical representation areas of the suprahyoid muscles in both cerebral hemispheres.

This group will include 19 patients. The patients in this group will receive 20 minutes of tDCS over the bilateral suprahyoid muscle cortical areas and 20 minutes over the bilateral cerebellar hemispheres.

This group will include 19 patients. The patients in this group received sham stimulation applied to the same area for the same duration.

Different experimental groups received tDCS stimulation at the following distinct sites: bilateral cerebellar hemispheres, bilateral cortical areas corresponding to the suprahyoid muscles, and combined bilateral cerebellar hemispheres alongside bilateral cortical areas corresponding to the suprahyoid muscles.

Stimulation parameters: 2 mA constant current, 20 minutes per session Treatment regimen: 5 sessions per week for 2 consecutive weeks

Process: A clinician-administered scale performed in three sequential parts. Part 1 examines basic clinical signs (e.g., consciousness, lip closure, voluntary cough). Part 2 involves observing the patient swallowing 5ml of water three times. If no abnormalities are detected, Part 3 requires the patient to swallow 60ml of water, noting the time and signs of aspiration.

Assessment: The total score (ranging from 18 to 46) is calculated. A higher score indicates more severe swallowing impairment.

Process: Patients will swallow barium-coated boluses of varying consistencies (liquid, semi-solid) under real-time X-ray (videofluoroscopy). The procedure is recorded for frame-by-frame analysis.

Assessment: The primary metric from VFSS will be the Penetration-Aspiration Scale (PAS ) score, which quantifies the depth and patient response to airway invasion. Additionally, the Dynamic Imaging Grade of Swallowing Toxicity (DIGEST) scale or component scores for oral and pharyngeal phase efficiency and safety may be used. A lower PAS score indicates better airway protection.

Process: Electrodes will be placed on the skin overlying the submental muscle group (suprahyoid muscles). Patients will perform swallowing tasks (e.g. saliva swallow, water swallow) while the electrical activity of these muscles is recorded.

Assessment:

1. Submental Electromyography (sEMG) Peak Amplitude (microvolts, µV): An indicator of the intensity of muscle contraction during swallowing, reflecting the degree of muscle effort.
2. sEMG Burst Duration (milliseconds, ms): The time interval from the onset of muscle activation to its return to baseline levels, reflecting the coordination and efficiency of the swallowing act.
3. sEMG Swallowing Waveform Morphology: The overall shape and pattern of the electrical activity signal during swallowing (e.g. a smooth, single-peak curve vs. a fragmented, multi-peak curve), used to assess the coordination of neuromuscular control. Changes in these parameters reflect improvements in the coordination and efficiency of the swallowing musculature.