Effect and neurophysiological mechanisms of transcutaneous auricular vagus nerve stimulation (taVNS) in misophonia: a single centre double-blinded randomised sham-controlled trial
Misophonia
After enrolling in the study, participants are invited to come to their first on-site visit, where they will complete baseline assessments before they are randomly allocated to receive either active taVNS or sham stimulation with the tVNS R device (tVNS Technologies GmbH). Random allocation sequencing is generated within SPSS (RV.UNIFORM(0,1)) by an independent research assistant not involved in any other aspect of the study. The randomisation order will be kept in numbered sealed envelopes such that participants get their assignment to the condition according to the order they enter the study. The tVNS R device has a stimulation unit and an ear electrode which delivers a low-voltage electrical signal to the ear. Stimulation is applied to the left ear, with active stimulation applied to the cymba concha (rich vagus nerve branch distributions) and sham stimulation to the superior scapha (no vagus nerve distribution). Electrical stimulation consists of a 25Hz wave delivered in 28s-on 32s-off bursts. Active and sham devices are identical, with the only difference being the stimulation location. An unblinded researcher (EMWK) will be setting the stimulation parameters for each participant and providing device training for at-home administration according to the randomisation schedule. The device is explained to the participant and then fitted by the EMWK to set stimulation intensity. Participants are instructed on how to use the device independently (both oral and written instructions for how to apply stimulation at home are provided). For maximum efficacy, stimulation intensity is adjusted and set to individual thresholds. We will ensure participant tolerance of stimulation by setting individual stimulation thresholds during device training. Current will be introduced at the lowest intensity (0.1mA) and gradually increased to a level at which the participant just begins to report discomfort (maximum intensity is 5mA). The device will then be adjusted to an intensity
1. Moderate to severe misophonia symptoms (scores >20 on the revised Amsterdam Misophonia Scale and scores >75 on the Sussex Misophonia Scale) 2. Not currently receiving active treatment for misophonia or planning to during the study 3. Aged between 18-40 years 4. Native English Speaker 5. Right-handed 6. No history of brain injury or neurological conditions 7. Normal or corrected to normal vision 8. Normal hearing (except for hyperacusis, tinnitus, or misophonia) 9. Owning and being willing to use a personal smartphone for tolerability questionnaires and stimulation reminders to be sent via a study app.
1. Are or could be pregnant 2. Have active implants (e.g., cochlear or other metallic implant, implanted vagal nerve stimulator, cardiac pacemaker) 3. Have a cerebral shunt (e.g., for the treatment of hydrocephalus) 4. Have wounds or skin diseases at or near the ear 5. Have a history or family history of heart problems (e.g., cardiac arrhythmias) 6. Have a history of seizures or epilepsy 7. Any other contraindications to an MRI scan