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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
100
Real NITESGON is delivered transcutaneously via two saline-soaked sponge electrodes (35 cm² each) positioned bilaterally over the C2 dermatomes to target the greater occipital nerve. Stimulation consists of a 20 Hz sinusoidal current at 1.5 mA peak-to-peak, ramped up over 30 seconds and ramped down over 5 seconds. It is administered concurrently with the task for \~45 minutes per session, across eight sessions (2/week) over 4 weeks.
Sham NITESGON is delivered using two saline-soaked sponge electrodes (35 cm² each) positioned bilaterally over the C2 dermatomes. The sham condition mimics real stimulation sensations via a 30-second ramp-up followed by a brief ramp-down, with no sustained current thereafter. Sham is administered concurrently with the task for \~45 minutes per session, across eight sessions (2/week) over 4 weeks.
ADT is delivered using a three-interval, three-alternative forced-choice (3I-3AFC) frequency discrimination task. Standard tone frequencies are individually selected using ERB/critical-band spacing, centered one octave below each participant's dominant tinnitus pitch and extending to lower frequencies; the highest standard is kept below the tinnitus pitch region. Tones are presented binaurally via headphones, with presentation levels calibrated to individual audiometric thresholds and matched for equal SPL in both ears.
VisDT uses a three-interval, three-alternative forced-choice (3I-3AFC) paradigm with Gabor patches (sinusoidal gratings windowed by a Gaussian envelope) of fixed spatial frequency (6 cycles/degree) and fixed spatial spread; on each trial, one interval contains an orientation deviant relative to the standard. During VisDT, participants attend to the visual task while concurrent binaural tones are presented passively using a predetermined, non-adaptive schedule. Auditory tones are individually calibrated to audiometric thresholds and drawn from ERB-spaced frequencies centered one octave below the dominant tinnitus pitch and extending to lower frequencies, with the highest frequency kept below the tinnitus pitch region.
Trinity College Institute of Neuroscience (TCIN)
Dublin, Dublin, Ireland
RECRUITINGTinnitus Loudness (Visual Analogue Scale, VAS 0-100)
0-100 mm VAS anchored from "not audible" to "extremely loud"; higher scores indicate greater perceived tinnitus loudness.
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Tinnitus Functional Index (TFI, 0-100)
25-item self-report measure of tinnitus-related functional impact; total score 0-100, higher scores indicate greater impairment.
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Tinnitus Handicap Inventory (THI, 0-100)
25-item measure of tinnitus-related handicap; total score 0-100, higher scores indicate greater handicap.
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Audiometry (Extended High-Frequency Thresholds up to 13 kHz)
Air-conduction pure-tone audiometry thresholds will be measured from 250 Hz up to 13 kHz (extended high-frequency audiometry) to characterise hearing status and support calibration of stimulus sensation levels.
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Speech-in-Noise Performance (e.g., QuickSIN)
Speech perception in noise will be assessed using a standardised speech-in-noise test administered in a controlled environment.
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Patient Global Impression of Change (PGIC)
Participant-rated global change since baseline using the Patient Global Impression of Change (PGIC) scale (-3 = very much worse to +3 = very much improved; higher scores indicate greater improvement).
Time frame: End of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Quality of Life (World Health Organization Quality of Life-BREF questionnaire)
Quality of life assessed using the World Health Organization Quality of Life-BREF (WHOQOL-BREF), yielding domain scores and an overall score (0-100; higher scores indicate better quality of life).
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Adverse Events (Stimulation Side-Effects Questionnaire)
Stimulation tolerability assessed each visit using a Stimulation Side-Effects Questionnaire recording presence and severity of side effects (e.g., tingling, itching, headache) rated on a numeric severity scale (0-10; higher scores indicate worse side effects), plus event frequency.
Time frame: Up to 4 weeks (Sessions 1-8)
Tinnitus Pitch Matching
Dominant tinnitus pitch estimated by psychoacoustic pitch matching and recorded as frequency in hertz (Hz).
Time frame: Baseline, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Tinnitus Loudness Matching and Discomfort Levels
Loudness matching and discomfort levels: Tinnitus loudness matching recorded in decibels sensation level (dB SL; dB above audiometric threshold) at the matched frequency, and loudness discomfort levels recorded in decibels sensation level (dB SL; dB above threshold) at tested frequencies.
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Minimum Masking Level (MML)
Broadband noise level required to fully mask tinnitus, recorded in decibels hearing level (dB HL).
Time frame: Baseline visit, end of treatment at 4 weeks, 28 days post-treatment, and 6 months post-treatment.
Resting-State EEG Spectral Power (Eyes Closed)
Resting-state eyes-closed electroencephalography (EEG) spectral power averaged within prespecified frequency bands and electrode/network regions, reported in decibels (dB); higher values indicate greater spectral power.
Time frame: Baseline visit, end of treatment (4 weeks), 28 days post-treatment, and 6 months post-treatment.
Resting-State EEG Functional Connectivity (Eyes Closed)
Resting-state eyes-closed EEG functional connectivity within prespecified networks, quantified as phase-locking value (PLV; unitless, 0-1); higher values indicate stronger phase synchronization.
Time frame: Baseline visit, end of treatment (4 weeks), 28 days post-treatment, and 6 months post-treatment.
Auditory Oddball Task-Evoked Response Amplitude
Auditory oddball event-related potential (ERP) amplitude (e.g., P300) averaged over prespecified electrodes/time windows, reported in microvolts (µV); higher absolute amplitude indicates larger task-evoked response.
Time frame: Baseline visit, end of treatment (4 weeks), 28 days post-treatment, and 6 months post-treatment.
Auditory Oddball Task-Evoked Response Latency
Auditory oddball ERP component latency (e.g., P300 peak latency) within prespecified time windows, reported in milliseconds (ms); lower values indicate faster evoked responses.
Time frame: Baseline visit, end of treatment (4 weeks), 28 days post-treatment, and 6 months post-treatment.
Pupillometry
Task-related pupil diameter during pupillometry, summarized as mean (or peak) pupil size change from baseline, reported in millimeters (mm); larger values indicate greater pupil dilation.
Time frame: Baseline visit, end of treatment (4 weeks), 28 days post-treatment, and 6 months post-treatment.
Heart Rate
Electrocardiography (ECG)-derived heart rate, reported in beats per minute (bpm); higher values indicate faster heart rate.
Time frame: Baseline visit, end of treatment (4 weeks), 28 days post-treatment, and 6 months post-treatment.
Saliva Biomarkers
Concentration of prespecified salivary biomarkers of arousal/neuromodulatory engagement, reported in nanograms per milliliter (ng/mL) (or assay-specific units); higher values indicate higher biomarker concentration.
Time frame: Baseline visit, end of treatment (4 weeks), 28 days post-treatment, and 6 months post-treatment.
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