Noninvasive Brain Stimulation Promising for Refractory Tinnitus

By David Douglas

July 20, 2020

NEW YORK (Reuters Health) - A network meta-analysis of randomized clinical trials indicates that central noninvasive brain stimulation may be of value in managing tinnitus, according to a multi-national group of researchers.

As Dr. Cheng-Ta Li, told Reuters Health by email, "Emerging evidence suggests non-invasive brain stimulation holds promise for treating refractory tinnitus."

"The latest network meta-analysis from Taiwan," he and coauthor Dr. Ping-Tao Tseng said, "reveals that cathodal transcranial direct current stimulation over left dorsolateral prefrontal cortex in combination with transcranial random noise stimulation over bilateral auditory cortex has the best efficacy and acceptability."

In a paper in JAMA Otolaryngology-Head and Neck Surgery, Drs. Li and Tseng of Taipei Veterans General Hospital, in Taiwan, and their colleagues note that somatic treatments can be effective in tinnitus with a specific origin such as loss of cochlear hair cells or ototoxic drugs. However, none has been proven to be effective in treating tinnitus without a specific cause.

Functional brain imaging studies in such patients have shown abnormal hyperactivity in the whole brain, especially in both auditory cortices. Suppressing such hyperactivity via central noninvasive brain stimulation (NIBS) has been proposed as a tinnitus-management strategy, but the results have been inconclusive.

The researchers examined the literature and identified 32 randomized controlled trials, including 1,458 unique participants. Their mean age was 49.6 years and 34.4% were women. The central NIBS method was compared with sham, waiting list, or active controls.

Compared with controls, cathodal transcranial direct current stimulation over the left dorsolateral prefrontal cortex combined with transcranial random noise stimulation over the bilateral auditory cortex was associated with the greatest improvement in tinnitus severity.

Improvement in tinnitus severity ranked more favorably for continuous theta-burst stimulation (cTBS) over both auditory cortices than cTBS over only the left auditory cortex.

Compared with strategies without priming, repetitive transcranial magnetic stimulation with priming had a superior effect. Also, say the researchers, "None of the investigated NIBS types had a significantly different dropout rate compared with that of the control group."

However, they caution that, "because some of the intervention comparisons were based on only a few RCTs, clinicians should select specific treatments with caution and avoid the one-size-fits-all treatment for all clinical conditions."

Dr. Berthold Langguth of the University of Regensburg, in Germany, a neurologist and an expert in tinnitus, noted, "An important finding is that the interventions are safe and that there is a clear trend towards efficacy of the different NIBS methods for tinnitus treatment. One has to consider that the number of available studies is still relatively small for some of the interventions. Therefore, some of the results should be interpreted with caution and need further replication. This has also been clearly stated by the authors in the discussion."

"Altogether this meta-analysis highlights the potential of non-invasive brain stimulation for tinnitus treatment and the need for further research in this area," Dr. Langguth concluded. "Considering the heterogeneity of tinnitus, one should aim at identifying predictors for the response to the various treatment, which finally could lead to an individualized treatment."

Dr. Harrison Lin of the University of California Irvine Center for Hearing Research, told Reuters Health y email, "This is an important and well-executed study that provides more evidence to support the use of interventions that treat tinnitus at the level of the brain, rather than at the ear. I agree with the authors that even more sophisticated studies are needed to definitively prove the benefit of non-invasive brain stimulation to patients with severe tinnitus symptoms."

The research did not have commercial funding.

SOURCE: JAMA Otolaryngology- Head and Neck Surgery, online July 9, 2020.