We aimed to analyze the effect of continuous dual session tDCS in patients with severe chronic subjective tinnitus without any evidence of hearing loss in terms of relief of tinnitus perception, distress, and loudness. Also, we investigated the difference in the maintenance duration of the tinnitus suppression effect of consecutive dual session tDCS compared to other groups followed up for 2 months.

The participants were randomly allocated with three different arms (control, single-session, and dual session) using block to balance the size of each group. Pure tone audiometry, speech audiometry, tinnitogram (pitch matching, loudness, minimal masking level and residual inhibition), auditory evoked potential, THI, visual analogue scale (VAS) of loudness, awareness and annoyance, and BDI were evaluated as a baseline tests. Participants who assigned to the control group underwent dual sham stimulation per day, twice a week for 1 month. Patients were received sham and true stimulation once alternately in the single session group and two true stimulation per day in the dual session group for the same period as the control group. All subjects who enrolled this study were given a conventional treatment such as tinnitus retraining therapy, sound therapy using sound generator, and medications like clonazepam, selective serotonin reuptake inhibitors for patients who wanted to take for relief of symptoms.

Inclusion Criteria:

• Individuals who have experienced subjective tinnitus for over 3 months.
• Individuals with normal hearing, defined as an average pure tone threshold of less than 25 dB between 0.5-4 kHz, and the presence of the V wave at 30 dBnHL with a difference in V wave latency of less than 0.2 ms in both ears during the ABR test.
• Individuals with severe tinnitus, as indicated by a Tinnitus Handicap Inventory (THI) score of 58 or higher, and who have been assessed for symptoms of anxiety and depressive mood using the Beck Depression Inventory (BDI) questionnaire.

Exclusion Criteria:

• Those requiring treatment for neurological disorders such as epilepsy, migraine, or intracranial masses.
• Pregnant individuals on the day of providing consent and those with metal-based electric implantable prosthetics.
• Individuals with objective or somatic tinnitus, auditory hallucinations, unwillingness to provide written consent, or unwillingness to continue the trial, and those who have participated in previous trials involving tDCS for tinnitus.