High-definition Transcranial Electrical Stimulation for Upper Extremity Rehabilitation

Pre- and 3-month change in motor function of the upper limbs assessed by Fugl-Meyer Assessment of Upper Extremity (FMA-UE),Pre- and 3-month change in motor function of the upper limbs assessed by Action Research Arm Test (ARAT)

Upper limb hemiparesis is the most common sequelae in patients, severely impacting their
 independence and quality of life. Transcranial electrical stimulation (tCES) is a
 non-invasive and safe treatment, which uses a low direct current or alternating current to
 change the excitability of the cerebral cortex. It can induces long-term potentiation-like or
 long-term depression-like effects, thereby modulating the cortical excitability. In recent
 years, researchers have developed high-definition (HD) devices, which integrate high
 definition ring electrode configurations and incorporate direct current with theta burst
 stimulation waveforms. Diverging from traditional transcranial direct current stimulation
 (tDCS), which applies weak currents (0.5-2 mA) through two large sponge electrodes (25~35
 cm^2) externally to the scalp for widespread non-specific cortical stimulation, HD-tES
 employs an array of small-area electrodes (1 cm^2) to control current distribution over
 localized cortical regions, thereby enhancing spatial accuracy. However, there is a lack of
 studies validating the optimal waveform for HD-tES, as well as clinical evidence in subacute
 stroke populations. The optimal unilateral versus bilateral stimulation modes and their
 neurological mechanisms for stroke rehabilitation also remain uncertain.