Imagine hearing a constant whistling, buzzing, hissing or beeping in your ear. Especially at night, if you want to sleep. Approximately every fourth person has the colloquial "ringing in the ears" in the course of his life. At least that's what they report. And here lies the problem: With very few exceptions, where the noise is audible from the outside via a stethoscope, only those affected perceive the sounds. Therefore, there is still a lack of an objective measurement method for tinnitus.
Now, however, scientists were able to show that the brain stem audiometry-in the English "Auditory Brainst Response", ABR ABR-is a tried and tested means to diagnose chronic tinnitus. You reported this in the magazine "Journal of Clinical Investigation". As for an EEG, electrodes in the forehead area are glued on. The electrical activity in the brain stem regions of the hearing lane is then measured while the test subjects perceive tones.
In tinnitus, it is assumed that the potentials measured in this way are changed – in their strength and/or in their temporal occurrence. Although the method is not new, researchers have so far disagreed as to whether the chronic ear noises can really be reliably detected in this way. It was also unclear which of the waves generated in the brainstem were useful as biomarkers: the electrical signals from the auditory nerve, from the olive stones or perhaps from the inferior colliculi?
The team led by Christopher Cederroth has carried out the largest study on this to date. The researchers recruited a total of more than 400 subjects. Half of them reported tinnitus in various forms, the other half reported no such symptoms. Using ABR, the scientists were able to show that the brain stem potentials of those who complained of a permanent ringing in the ears differed from those who heard only occasional or no disturbing noises at all.
Tinnitus and delayed brain stem potential
Thus, the wave emanating from the inferior colliculi in the brainstem was delayed in them. Those affected by tinnitus only occasionally did not differ in this respect from the subjects without ear noises. According to the researchers, ABR is a sensitive biomarker for detecting chronic tinnitus.
To find out more about the course of the disease, Cederroth and his team also evaluated the data of 20,000 people recorded in a Swedish long-term study. As a result, people with occasional ear noises have an increased risk of developing permanent tinnitus. "We need to disseminate these results so that people who have a beeping in their ear from time to time are aware of the risks and have the chance to do something about it, " says the biologist.
There is currently no therapy with which the cause can be treated. Most treatments aim to ensure that patients learn to live with tinnitus. But hearing aids can also help in some cases. With the help of the brain stem EEG, better treatment options may be developed because the success of potential treatment can be measured.
