Cerebellar Transcranial Direct Current Stimulation for Dysphagia After Supratentorial Stroke

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:

• Submental Electromyography (sEMG) Peak Amplitude (microvolts, µV): An indicator of the intensity of muscle contraction during swallowing, reflecting the degree of muscle effort.
• 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.
• 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.

Process: Using a 3.0T MRI scanner, high-resolution T1-weighted anatomical images and resting-state fMRI (rs-fMRI) data will be acquired. During rs-fMRI, patients will remain awake, relaxed, and with their eyes open, without performing any specific task.

Assessment: Analysis will focus on changes in functional connectivity (FC) within the swallowing network, particularly between the cerebellum, primary sensorimotor cortex, and brainstem. Regional changes in the amplitude of low-frequency fluctuations (ALFF) or cerebral blood flow (CBF) will also be examined to identify alterations in local neural activity.

Process: A single-voxel MRS sequence will be performed. Voxels will be placed in key regions of interest (ROIs), including the bilateral swallowing motor cortex and the cerebellar hemispheres.

Assessment: The concentrations of key neurometabolites-N-acetylaspartate (NAA, a marker of neuronal integrity), Choline (Cho, related to membrane turnover), Creatine (Cr, an energy reference), Gamma-Aminobutyric Acid (GABA, the primary inhibitory neurotransmitter), and Glutamate (Glu, the primary excitatory neurotransmitter)-will be quantified. Changes in ratios (e.g., NAA/Cr) or absolute concentrations will indicate neuroplastic and neurochemical changes.

Process: A 32-channel digital EEG system will record brain electrical activity for at least 10 minutes in a resting state (eyes closed). Data will be carefully inspected to remove artifacts.

Assessment: The power spectral density of key frequency bands (Delta, Theta, Alpha, Beta) will be analyzed. Primary QEEG metrics will include the Brain Symmetry Index (BSI) to assess interhemispheric balance and the Delta + Theta/Alpha+Beta Ratio (DTABR), which serves as an indicator of overall brain arousal and cortical inefficiency. A decrease in DTABR suggests a shift towards a more alert and efficient brain state.