Bimodal Electrical-Sound Stimulation and Auditory Training for Chronic Tonal Tinnitus

Non-Invasively Re-Training the Tinnitus Brain Using Bimodal Electrical-Sound Stimulation (NITESGON-ADT): Protocol for a Prospective, Double-Blind, Randomised Controlled Trial

This study tests whether pairing non-invasive stimulation of the greater occipital nerve (NITESGON) with an attentionally demanding auditory frequency discrimination training task reduces tinnitus loudness and tinnitus-related distress. One hundred adults with chronic tonal tinnitus will be randomised to one of four groups in a 2×2 factorial design: real versus sham NITESGON and active versus passive listening during auditory stimulation. Participants complete eight sessions across four weeks, with outcomes assessed at baseline, end of treatment, 28 days post-treatment, and 6 months post-treatment.

This is a single-centre, prospective, double-blind, placebo-controlled, 2×2 factorial randomised controlled trial conducted at Trinity College Dublin. The intervention combines transcutaneous electrical stimulation targeting the greater occipital nerve (NITESGON) with auditory stimulation delivered during a structured training paradigm. The two between-subjects factors are stimulation condition (real NITESGON vs sham NITESGON) and listening condition (active listening: auditory frequency discrimination training vs passive listening: visual distractor task while auditory stimuli are presented). One hundred adults with chronic tonal tinnitus will be randomised 1:1:1:1 to one of four arms. Participants complete eight sessions (two per week for four weeks). Primary outcomes-tinnitus loudness (VAS 0-100), tinnitus-related functional impact (TFI 0-100), and tinnitus handicap (THI 0-100)-and secondary outcomes are assessed at baseline (T0), end of treatment (T1), 28 days after treatment completion (T2), and 6 months after treatment completion (T3). Secondary outcomes include tinnitus psychoacoustics, extended high-frequency audiometry, speech-in-noise performance, EEG (resting-state and auditory oddball), autonomic/biomarker measures (pupillometry, heart rate, saliva), patient global impression of change, quality of life, and safety/blinding assessments.

Inclusion Criteria:

• Adults aged 18-80 years
• Continuous subjective tinnitus for >3 months and ≤5 years
• Predominantly tonal tinnitus (unilateral or bilateral)
• Screening THI score 28-76
• Minimum Masking Level (MML) 20-80 dB HL
• No prior tinnitus neuromodulation treatment
• Able to comply with eight sessions over four weeks and follow-up assessments

Exclusion Criteria:

• Objective tinnitus or predominantly somatic tinnitus
• Pulsatile tinnitus
• Evidence of conductive hearing loss (abnormal otoscopy or tympanometry)
• Pure-tone audiometry exclusions: >40 dB HL at any frequency 250 Hz-1 kHz OR >80 dB HL at any frequency 2-8 kHz in either ear
• Hearing aid use initiated within the past 90 days
• Active implantable medical device (e.g., pacemaker, DBS, cochlear implant)
• LDL <30 dB SL at 500 Hz in either ear
• Diagnosis of temporomandibular joint disorder or occipital neuralgia
• Severe anxiety (STAI >120/160)
• Cognitive impairment (MMSE <25)
• Severe depressive symptoms (BDI ≥30)
• Diagnosis of Menière's disease
• Current pregnancy
• Involvement in medicolegal cases
• History of auditory hallucinations
• Current prescription of central nervous system drugs likely to alter neuromodulatory function (e.g., noradrenergic, dopaminergic, serotonergic, benzodiazepine, cholinergic, or other psychoactive medications)
• Currently enrolled in another interventional study