Effect of Phase-Locked Transcranial Alternating Current Stimulation on Vocal tremor

Vocal tremor can be found in 30% of patients with essential tremor, causing significant communication difficulties. To develop more efficient and safer treatments with less side effects for vocal tremor, this study investigated the potential of transcranial alternating current stimulation (tACS) that is temporally synchronized with tremor envelope. Three female patients with vocal tremor received tACS over the cerebellum during their phonation. Patients received phase-locked stimulation of both in-phase and out-phase with respect to the tremor, and the changes in voice characteristics was evaluated. The results showed that out-phase stimulation significantly reduced tremor amplitude intensity (AtrI). After the treatment, the patients' subjective ease of phonation improved. These findings suggest that tACS, especially out-phase stimulation, can be an effective treatment for vocal tremor and warrants further study.