New tinnitus therapy developed

Tinnitus: US researchers developed a new therapeutic approach and switched off the ear noises

14.01.2011

Is tinnitus curable soon? US scientists have succeeded in animal experiment by the stimulation of the tenth cranial nerve (vagus nerve), the cause of annoying permanent noise in the ear off.

The Vagus Nerve Stimulation procedure, which has been used to treat epilepsy and depression, could also alleviate tinnitus symptoms, the US researchers report in the latest issue of the journal „Nature“. As part of their study, the scientists had tested the procedure on rats and achieved significant success here. „We change the brain - from a state that produces tinnitus to a state where it does not produce tinnitus“, explained Michael P. Kilgard from the University of Texas at Dallas. The expert emphasized: „We eliminate the origin of tinnitus.“

Tinnitus develops in the mind of those affected
Although the causes of tinnitus have not yet been clearly researched, damage to the sensory cells in the inner ear has been a potential trigger for years. Similar to phantom pain after amputation, tinnitus is therefore the result of sensory deprivation. „underemployed“ Neurons in the auditory cortex generate, according to the US researchers hearing sensations that exist only in the brain of those affected. Heavy noise, in particular, causes symptoms, as evidenced by the high prevalence of 40 percent among US veterans suffering from severe tinnitus after (loud) warfare, the US scientists said. Generally, tinnitus is „Noise in your own head“, which is perceived only by those affected as whistling, hissing, hissing, screaming, humming or humming. Even if the phenomenon usually only occurs for a short time and the sounds pass by again, the persistent noise becomes a constant companion for some tinnitus patients. Those affected are barely able to rest, as they are constantly plagued by an unpleasant continuous tone that is particularly noticeable at night or when it is actually quiet in the outside world.

Tinnitus is not an independent disease but a symptom
Tinnitus is not a disease on its own, but merely a symptom of damage in the auditory pathway that can be triggered by a variety of causes, said the researchers University of Texas. For example, tinnitus can be triggered by organic conditions such as noise, malformations or inflammation. In addition, mental factors in the development of tinnitus also play a role, said the US researchers. The usual treatment approaches focus so far mostly on the annoying tones to cover or teach those affected to ignore them - sometimes more, sometimes less successful, as the US scientists report. However, research has made significant progress in recent years, and physicians today understand far better why the annoying persistent noises even occur, stressed the scientists of the University of Texas.

Conversion of nerve connections due to damage in the ear canal
Thus, the US researchers assume that the cause of the phenomenon is not to be found in the ears but in the brain of those affected. Damage to the ear canal would lead to a rebuilding of the neural connections, which redistributes tasks that the injured areas can no longer perform, explained the experts. As a result, certain brain areas are subsequently overactive and in some cases produce the phantom sounds known as tinnitus. The frequency of the perceived sounds lie on just those frequencies at which no stimuli can be processed because of the damaged hearing, the US researchers continue. As part of their study, Michael Kilgard and colleagues have now, based on the findings on the development of tinnitus, a new therapeutic approach tested with the aim of the brain „to work out“. By specifically stimulating the vagus nerve with artificial signals, the remodeling of the nerve connections can be undone and a kind of re-start of the affected brain areas can be made, explained the US researchers.

New procedure for tinnitus treatment
The scientists have used the novel method of combating tinnitus for the first time in animal experiments with rats. The US researchers exposed some of the animals under general anesthesia very loud noise, whereby the rodents on the appropriate frequency developed a tinnitus. The eight animals were given a nine-kilohertz sound 300 times a day for 20 days, with the sound associated with mild electrical stimulation of the vagus nerve, Kilgard and colleagues report. By this treatment, the number of nerve cells in the auditory cortex, which responded to this frequency, compared to animals of the control group increased by 79 percent, according to the US researchers. Subsequently, in a second experiment, the scientists played the sounds of two different frequencies (four and 19 kilohertz) to the rats, but only connected the higher frequencies with the stimulation of the vagus nerve. As a result, the number of neurons that belonged to the higher tone increased by 70 percent, while the number of neurons in the range of lower frequency dropped, scientists explained.

Stimulation of the vagus nerve crucial
The results of these first experimental tinnitus tests in rats have shown that it is not the sound alone that is responsible for the appearance of the phenomenon, but that the parallel stimulation of the vagus nerve (vagus nerve) leads to the development of a corresponding tinnitus affection, the scientists explained. The decisive factor is obviously the processing of the acoustic stimuli in the cerebral cortex in the so-called auditory cortex, the US researchers continue. Since they assume that the tinnitus is triggered by an overactivity of the brain areas in the range of the corresponding frequencies, the US scientists tested in the following experimental step, whether the tinnitus in the rats can be resolved when the animals - with simultaneous stimulation of the vagus nerve - Sounds that are around the frequency of tinnitus sound around.

Treatment of tinnitus based on vagus nerve stimulation
The US scientists played the tinnitus-affected rodents 300 times a day for three weeks tones at a different frequency than the tinnitus tone, accompanied by a corresponding vagus nerve stimulation. The neurons of the auditory cortex were rebuilt in the course of treatment so that they respond to their original frequencies, said the US researchers. Also the typical physiological and behavioral reactions of the rats, which were connected with the Tinnitus, had no longer occurred and the number of nerve cells of the treated rats had returned to the normal measure, emphasized Kilgard and colleagues. The changes have remained stable for a long time after treatment, the US scientists continue. „The key is that, unlike previous treatments, we do not mask tinnitus“, stressed Michael P. Kilgard.

Review tinnitus treatment method in clinical trials
The stimulation of the vagus nerve is not a novelty in medicine, but such procedures have not been used to treat tinnitus. Vagal nerve stimulators designed for human use are pacemaker-sized devices that are implanted beneath the clavicle of the patient and send stimulation pulses to the tenth cranial nerve. The treatment of tinnitus with the newly tested in animal experiments novel method to be tested according to the US researchers next in a clinical study. However, by the time the trials move into the clinical phase, the researchers say they want to further refine the process and understand more details of the effect. It is interesting, for example, how long the treatment should last and whether not only acute tinnitus but also chronic tinnitus can be corrected. (Fp)