Repetitive transcranial magnetic stimulation
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive treatment involving a magnetic coil, held over the head of a patient by a mechanical arm, which uses rapidly changing magnetic fields to generate weak electric currents and excite neurons in the brain.
It is a new approach currently being researched in Germany and the USA for the treatment of tinnitus that has developed out of the use of imaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), which have recorded brain activity in tinnitus sufferers who are able to modify their tinnitus (known as somatic modulation).
As tests have shown that areas of the brain that process information from the ears are more active in tinnitus sufferers than in people without the condition, researchers are looking to see whether the use of rTMS can alter this brain activity and whether this will lead to a longer term reduction in tinnitus symptoms. Patients involved in early trials of this treatment have undergone daily sessions lasting between 20 - 40 minutes, for a period of one or two weeks.
There have been some positive results with the treatment showing some tinnitus reduction for some patients. However, the reduction in symptoms has only been for short periods of time.
One study showed that rTMS resulted in partial suppression of tinnitus for six out of 15 subjects, with the amount of suppression ranging from 19% to 86% (average 50%). The duration of tinnitus suppression for each of the six subjects was: 20 min, 30 min, 45 min, 60 min, and one and four days, respectively.
A second study tested rTMS for the treatment of tinnitus in 60 patients over a 10-day period. Results showed that there was a remarkable reduction in tinnitus after active stimulation and tinnitus improvement lasted up to three months in some patients. However when treatment was discontinued, the tinnitus returned in all cases.
Trials of the treatment have so far been small, using varying research methods, and with varying results. In order to improve the potential of rTMS as a treatment for tinnitus, it is necessary to replicate the findings in larger scale studies and to follow up the patients over the long term, as well as to understand how to optimise aspects of treatment including positioning of the magnetic coil.
Professor David McAlpine of the UCL Ear Institute says “Currently we know very little about the basis of rTMS, or why it might be effective in short-term suppression of tinnitus. It is also also unclear what might be the long term effects of using a large magnetic impulse on the brain. For someone with severe tinnitus, there may well be an effect of the treatment, but this effect may be on the whole of the brain and it could inhibit or switch off a part. In addition, although rTMS may inhibit activity in the brain which seems to be associated with tinnitus, the origins of tinnitus are not yet fully understood, so it may be a case of only treating the symptoms during the stimulation, without treating the cause. We have to be careful about interpreting what is going on.”
The treatment is not yet available in the UK and it is unlikely to become established here until there is a greater body of evidence for its effectiveness and safety.
