Imagine hearing a constant whistling, buzzing, hissing or beeping in your ear – even at night when you want to sleep. With silence, the phantom noises become even more distressing. Approximately every fourth person is tormented by the colloquial “ringing in the ears” in the course of their life. At least that’s what they report. And here’s the problem: there has been a lack of an objective measurement method so far. Because with a few exceptions, where even outsiders can hear the beeping, only those affected perceive the noise. An objective criterion would not only be important to quantify the suffering, but also to be able to develop better therapies for tinnitus. This is the only way to measure the success of the treatment.
Scientists from the Karolinska Institute in Stockholm, among others, have now been able to show that so-called brainstem audiometry (auditory brainstem response, abbreviated ABR) is a tried and tested means of diagnosing chronic tinnitus. Similar to an EEG, electrodes are attached to the forehead area. The electrical activity in the brainstem regions of the auditory pathway is then measured while the subjects perceive sounds.
In the case of tinnitus, it is assumed that the potentials measured in this way have changed – in terms of their strength and/or the time at which they occur. However, this procedure is not new. So far, however, researchers have been at odds as to whether chronic ear noises can really be reliably detected in this way and which of the waves generated in the brainstem are useful as biomarkers: are they the electrical signals from the auditory nerve, the olive nuclei or perhaps from the inferior colliculi ?
Christopher Cedderoth’s team has now carried out the largest study to date. The researchers recruited a total of over 400 test subjects – half of them reported various degrees of tinnitus, the other half no such symptoms. Using ABR, the scientists were able to show that the brainstem potentials of those who complained of constant ringing in their ears differed from those who only heard occasional noises or none at all.