Date: Tuesday 2nd July, 2013
A great number of people all over the world suffer from the sometimes debilitating symptoms of tinnitus. Depending on the severity of the condition it can often lead to a reduced quality of life. Constant ringing, buzzing and even roaring noises can cause depression, anxiety and often a lack of sleep. There are therapies available to help people manage the symptoms and even hearing aids that have programs to mask the noise but, at present there is no cure.
Tinnitus can be caused by a number of things but one of the most common is exposure to loud noises, either prolonged or from a sudden blast of sound. Although portable music players and loud concerts are major culprits it tends to be people who work in certain environments that are most likely to develop the condition. Nightclub workers, construction or factory workers and even soldiers are at a significantly higher risk due to often prolonged exposure to very loud noises. As many of these professions are essential, a way needs to be found to protect people against this condition and if possible, stop any damage occurring as the preventative measures currently in place have proven ineffective in many cases.
As tinnitus cannot be cured at the moment, scientists and researchers from the Otolaryngology department at the Pittsburgh School of Medicine in the US began looking into the reason tinnitus develops in the hope of finding a way to prevent it.
It has been found that tinnitus occurs when there is hyperactivity in the auditory center of the brain known as the Dorsal Cochlear Nucleus (DCN). When these DCN cells are affected they will fire impulses even when there is no sound, leading to the phantom noises associated with tinnitus. The cause of this hyperactivity was identified as a reduction in KCNQ channel activity. Normally, potassium ions move in and out of the cells through the KCNQ channels and effectively block these unnecessary impulses. So, in order to stop the hyperactivity in the DCN cells, they needed to find a way to restore normal KCNQ channel activity.
The answer came through a drug called Retigabine. This drug is currently used for the treatment of epilepsy but the tests have produced some interesting and potentially exciting results.
In these tests, sedated mice were exposed to prolonged sessions of loud noise. The noise intensity was approximately the decibel level of an ambulance siren which is loud enough to produce the symptoms of tinnitus. Half an hour into the exposure, half of the mice were injected with the Retigabine while the others were left untreated. The mice treated with the drug were given subsequent injections twice a day for the next five days. A week after the initial exposure, tests were conducted on all the mice to determine whether any tinnitus symptoms had developed. These tests involved using different sounds and observing the reaction from the mice. They alternated periods of sound with periods of silence and then pulsed one sudden loud noise at a random interval.
A subject with normal hearing is aware of the change when the sound stops and starts so is therefore much less startled when there is a further change when the loud noise is introduced. When tinnitus symptoms are present, a subject does not hear the silence in the same way due to the phantom ringing or buzzing noises.
When scientists analysed the data from the tests, the results were incredible. They found that all of the mice who had been treated with the Ritigabine had developed no symptoms of tinnitus, reacting normally to all sounds. From the untreated group, approximately 50% of the mice exhibited symptoms of the condition which was consistent with earlier research.
Much more research and testing is needed at this time as the drug as it is now, is not specifically made for this purpose. This means that a new drug must be developed using these results which would target the exact source of tinnitus while minimising the possibility of any side effects. With further development though, in the future this could provide a solution and potentially become an effective method of preventing the onset of tinnitus for people who work in high risk professions.