New initiatives in tinnitus research
10 July 2009
The Tinnitus Research Initiative (TRI) was founded in January 2006 as a privately funded organisation dedicated to finding a cure for tinnitus through clinical and scientific research. In June 2009, TRI held its third conference in Stresa, Italy, bringing an international group of researchers together to discuss past and present results and move the field of tinnitus research forward. Deafness Research UK attended the meeting to share ideas and to find out what has been achieved so far.
One of the key themes of the meeting was the development of treatments that use specially designed sounds to change or even reverse the brain activity that leads to tinnitus. Dr Grant Searchfield and his colleagues at the University of Auckland presented encouraging results from patients who were asked to group sounds that were similar in pitch to their own tinnitus together into one category. After three weeks of training there was both a reduction in the brain activity associated with the categorised sounds, measured using EEG, and a decrease in the level of tinnitus distress experienced by the patients. However, a study of PhaseOut treatment, by University Medical Centre, Groningen, showed that this treatment was no more effective than stimulating patients with a pure tone. PhaseOut uses a changing cyclic pattern which has been claimed to prolong tinnitus suppression. The study's findings did not support this claim.
A study at the University of Milan looked at the link between tinnitus and hearing loss. It was already known that most people with hearing loss have some degree of tinnitus but some sufferers of tinnitus appear to have normal hearing. Initial results from the study found that most of those with apparently normal hearing in fact appear to have at least mild hearing loss, especially at higher pitches that are often not tested in a standard audiogram.
Hearing aids are increasingly being used to treat tinnitus. Digital hearing aids alleviate tinnitus more effectively than analogue aids as they can selectively amplify some of the higher frequencies at which tinnitus generally occurs. Scientists at the meeting called for more research to develop digital hearing aids that can represent these frequencies more effectively and, importantly, using less battery power. It is thought that tinnitus results where the brain overcompensates for the loss of hearing at particular frequencies. Therefore, providing sufficient input at these should reduce tinnitus.
In 2007, eight patients with hearing loss and severe tinnitus were fitted with a Vibrant Soundbridge®, an implanted hearing aid that works by vibrating bones in the middle ear and is effective at higher frequencies. German researcher Dr Ebherd Biesinger found in a follow-up study two years later that, when switched on, the Vibrant Soundbridge® completely suppressed tinnitus in those patients for whom sound stimulation treatments had been found to work.
A study carried out jointly by the University of Antwerp and the University of Innsbruck followed 22 tinnitus sufferers over a period of two years. The patients had been fitted with a cochlear implant in one ear. They were all profoundly deaf in that ear and had severe tinnitus in the same ear. All 22 patients were found to experience a significant reduction in tinnitus loudness after 24 months with the cochlear implant.
There are currently no universally effective drug treatments for tinnitus. However, a presentation at the conference detailed how a new drug called neramexane is currently undergoing clinical trials at several centres internationally. Initial results from a previous, smaller trial were promising but inconclusive. The current trial will look at potential side-effects and how long any positive effects last. A review of trials using anticonvulsant drugs to treat chronic tinnitus found just one study with reliable results. The study found that gabapentin is not an effective treatment.
Finally, Professor Ana Belén Elgoyhen presented a promising target for drug development that may be effective for treating hearing loss and tinnitus. A mutation has been discovered in the hair cells of the outer ear of mice that protects the inner ear from noise-induced damage, potentially preventing both hearing loss and tinnitus. Future research will seek to develop a drug treatment that reproduces the effect of this mutation.
