Transcranial magnetic stimulation for tinnitus

Tinnitus can be described as the experience of sound in the ear or in the head. Subjective tinnitus is not heard by anyone else. The exact cause of tinnitus remains unknown. At present no particular treatment has been found effective in all patients. Recently, researchers have been able to image the brain using specialised techniques (such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET)). This has led us to believe that high spontaneous neuronal activity in the central auditory system and associated areas may responsible for the perception of tinnitus. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive means of inducing electrical currents in the brain and can decrease this neuronal activity. The purpose of this Cochrane Review was to assess the effectiveness and safety of rTMS for the treatment of tinnitus.

Our search for studies retrieved 283 articles. Of these, five trials comprising 233 tinnitus patients met our inclusion criteria and were included in the review.

The first study considered the use of 'complex waveform rTMS', the second looked at the use of high-frequency rTMS, and the other three studies considered the use of low-frequency rTMS. We found that the use of low-frequency rTMS resulted in 'partial improvement' in tinnitus severity and disability in one study, however these results were not replicated in two other studies that considered rTMS at the same frequency. Furthermore, this single positive finding should be taken in the context of the many different variables which were recorded at many different points in time by the study authors. We were able to demonstrate an improvement in tinnitus loudness in patients undergoing rTMS when we combined the results of two other studies.

rTMS is a safe treatment for patients with tinnitus in the short-term, however no data were available to verify safety in the long-term.

Authors' conclusions: 

There is very limited support for the use of low-frequency rTMS for the treatment of patients with tinnitus. When considering the impact of tinnitus on patients' quality of life, support is from a single study with a low risk of bias based on a single outcome measure at a single point in time. When considering the impact on tinnitus loudness, this is based on the analysis of pooled data with a large confidence interval.

Studies suggest that rTMS is a safe treatment for tinnitus in the short-term, however there were insufficient data to provide any support for the safety of this treatment in the long-term.

More prospective, randomised, placebo-controlled, double-blind studies with large sample sizes are needed to confirm the effectiveness of rTMS for tinnitus patients. Uniform, validated, tinnitus-specific questionnaires and measurement scales should be used in future studies.

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Background: 

Tinnitus is the perception of sound, in the ear or in the head, in the absence of any external acoustic stimulation. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive means of inducing electrical currents in the brain, and has received increasing attention in recent years for the treatment of many neuropsychiatric disorders, including tinnitus.

Objectives: 

To assess the effectiveness and safety of rTMS versus placebo in patients with tinnitus.

Search strategy: 

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the most recent search was 24 May 2011.

Selection criteria: 

Randomised controlled trials of rTMS versus sham rTMS.

Data collection and analysis: 

Two review authors reviewed the titles, abstracts and keywords of all records retrieved. Three review authors independently collected and extracted data, and assessed the risk of bias of the trials.

Main results: 

Five trials comprising of 233 participants met our inclusion criteria. Each study described the use of a different rTMS device that delivered different waveforms at different frequencies. All five trials were relatively small studies but generally they demonstrated a low risk of bias.

When considering the impact of tinnitus on patients' quality of life, the results of only one study demonstrated a statistically significant improvement in Tinnitus Handicap Inventory (THI) scores at four months follow-up (defined as a 'partial improvement' by the study authors (THI reduction of 21% to 80%)) when low-frequency rTMS was compared with a sham control treatment. However, no statistically significant improvement was demonstrated by another two studies that considered rTMS at the same frequency. Furthermore, this single positive finding should be taken in the context of the many different variables which were recorded at many different points in time by the study authors.

In accordance with our pre-specified subgroup analysis we extracted the data from one study to consider the differential effectiveness between 'lower' low-frequency rTMS (1 Hz) and 'higher' low-frequency rTMS (10 Hz, 25 Hz). In doing this we were able to demonstrate a statistically significant difference between rTMS employing a frequency of 1 Hz and the sham group when considering tinnitus severity and disability after four months follow-up ('partial' improvement). However, no statistically significant difference was demonstrated between 10 Hz and 25 Hz rTMS, and the sham control group, when considering the severity and disability of tinnitus at four months follow-up.

When considering tinnitus loudness in patients undergoing rTMS we were able to demonstrate a statistically significant reduction in tinnitus loudness when the results of two studies were pooled (risk ratio 4.17, 95% confidence interval 1.30 to 13.40). However, this finding was based on two small trials and consequently the confidence interval was particularly wide.

No serious adverse effects were reported in any of the trials.

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