Novel ‘infraslow pink noise’ stimulation found to be safe and feasible in chronic tinnitus

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Dirk De Ridder

A novel brain stimulation technique called high-definition transcranial infraslow pink noise stimulation (HD-tIPNS) was recently evaluated in a placebo-controlled pilot study, and found to be both safe and feasible in the treatment of chronic tinnitus.

However, writing in the journal Neuromodulation: Technology at the Neural Interface, Dirk De Ridder (University of Otago, Dunedin, New Zealand) et al report that electroencephalography (EEG) changes observed in the study were “unsupported by clinical benefit”. As such, they state that “further research is essential to evaluate the potential of this multifocal network stimulation approach”.

“Tinnitus has been linked to activity and connectivity changes in the auditory cortex (AC), parahippocampus (PHC), and posterior cingulate cortex (PCC),” the authors write, introducing the premise for their study. “Although previous studies have targeted these areas individually, no study has yet modulated them simultaneously. Furthermore, novel stimulation designs may be superior to traditional alternating or direct current stimulation.”

On this basis, De Ridder and colleagues investigated the feasibility and safety of HD-tIPNS for treating chronic tinnitus targeting the AC, PHC, and PCC via a pilot study with a double-blind, randomised, placebo-controlled, parallel-arm design. A total of 20 chronic tinnitus patients received 12 sessions—three per week for four weeks—of either HD-tIPNS or ‘acti-sham’ stimulation, with clinical outcomes being collected at baseline, three days and 10 days after treatment.

Primary outcomes included feasibility, safety, and resting-state EEG measures, while secondary outcomes included tinnitus and quality-of-life metrics assessed using questionnaires. According to the authors, participants were “rapidly recruited” and adhered to the study protocol with “minimal difficulty”. This, coupled with a dropout rate of 13% and the fact the treatment approach was “acceptable” to participants, supports the feasibility of the protocol, they add.

De Ridder et al relay that there were no long-term adverse events observed, with only mild side-effects like headaches and dizziness being reported, indicating the safety of this form of stimulation. In addition, tinnitus measures were similar between HD-tIPNS and acti-sham stimulation.

Resting-state EEG analyses also revealed decreased beta-1 activity in the PCC 10 days after acti-sham treatment, and the HD-tIPNS group demonstrated decreased beta-1 activity in the inferior parietal lobule three days after treatment. Finally, De Ridder and colleagues report finding an increase in functional connectivity in the beta-1 frequency between the left and right PHC in the HD-tIPNS group—compared to the acti-sham group—three days after treatment.


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