Opinion of the technical advisory board of the German Tinnitus League e. V.
Bimodal stimulation for tinnitus treatment (Lenire)
In the meeting of the technical advisory board of the German Tinnitus League e. V. (DTL) in February 2021, the study situation on bimodal stimulation was discussed in great detail. Bimodal means "in two ways"; What is meant here is both electrical and acoustic stimulation. This method is based on animal experiments, in which it could be shown that learning effects can be improved by stimulating certain centers of the cerebral cortex. With regard to tinnitus, a learning effect is to be achieved in order to be able to ignore the tinnitus, if one simultaneously couples tones which are adjusted in a certain relation to the tinnitus with an electrical stimulation.
Such a therapy was presented a few years ago, in which the 10th cranial nerve, the vagus nerve, was stimulated in the neck, either by electrodes attached or by an electrode that was directly implanted. Here, too, the electrical stimulation was carried out for a certain time during the day and connected with the hearing of tones. With this bimodal vagus irritation, however, no really lasting successes for tinnitus treatment could be reported in the 2014 studies (Tyler et al., 2017).
A study group led by Prof. Shore from the USA pursued a different approach in 2017, which focuses on so-called somatosensory tinnitus, i.e. the form of noises in the ear that are essentially related to disorders and functional restrictions of the cervical spine or the masticatory muscles. The study group tried to stimulate another cranial nerve, the trigeminal nerve, and to couple this stimulation with acoustic stimulation. In this treatment, electrodes were stuck to the cheek and forehead; the combined treatment also resulted in short-term improvements in tinnitus, which, however, did not last long and should be more successful if the tinnitus could be influenced by dysfunction of the masticatory muscles (Marks et al., 2017). A corresponding device is used in the USA for this purpose.
A newer variant of this treatment also stimulates part of the trigeminal nerve, the tongue nerve (nervus lingualis), and pairs this with acoustic stimulation after determining the tinnitus frequency. Here, too, a device is already on the market; the first studies have now been published. In Germany, this treatment is offered by the Neuromod company under the name Lenire.
The German Tinnitus League was asked by several authorities whether they should encourage their members to participate in these studies. According to our information, the device for this treatment costs around 2,700 euros. For the studies that are now being carried out or planned, the patients participating in the study have to pay for the equipment. For ethical reasons, however, from the point of view of self-help, studies in which the participants have to pay for participation in the study should be rejected as a matter of principle.
A current study in which the devices were placed on the patient was published by Conlon and co-workers in 2020; it is currently being commented on in the media as very promising. The study on this bimodal (tongue) stimulation reports on 326 patients who were stimulated in three therapy arms without placebo control. Overall, this group was selected from 698 patients who were found to be suitable for the therapy, although from our point of view it is not clear why the other patients apart from the 326 were not taken.
Overall, the three equally large stimulation groups differed in the stimulus parameters used, i.e. the current sequences that were applied to the tongue, and also in the acoustic stimuli associated with them. The third group in particular was stimulated with tones that were not directly paired with the electrical stimulation. There is no direct assignment to the tinnitus frequency for acoustic stimulation. Treatments were carried out for a total of twelve weeks with two 30-minute applications per day.
For the study, 80 percent of the patients could be evaluated, 20 percent did not fully participate in the study and were therefore excluded from the evaluation. After the treatment, all groups had improved statistically significantly on average, the findings being measured using appropriate questionnaires, the Tinnitus Handicap Inventory (THI) and the Tinnitus Functional Index (TFI). These questionnaires provide information about the burden of tinnitus. They were checked again after twelve months and appeared to have remained stable. However, 20 percent of the participants did not improve through the stimulation (Conlon et al., 2020).
From the point of view of the technical advisory board, one criticism of the study is that it does not include the extensive diagnostics relating to the hearing function, the tinnitus frequency and volume and counseling, as to whether an explanation of the causes and consequences of the Suffered from tinnitus or not. Since this information is known to have a high therapeutic effect, it should have been mentioned in the work from the point of view of the members of the Advisory Board.
It is also difficult to assess the fact that the individual hearing loss of the patient was recorded, but not further described in the study and, as far as recognizable, it was not evaluated whether there were differences in the success of the therapy with regard to the hearing loss.
It would also be desirable to discuss why the third group, which was actually unspecific in terms of acoustic stimulation, improved in the same way as the other groups. A placebo effect could at least be suspected here.
Noteworthy and actually the main point of criticism of the study is that, according to their own statements, eight of the total of 13 authors are directly employed by the company that also sells the device. Another three authors receive consultancy fees from this company. Therefore, at least the independence of the study can be doubted.
This study was discussed in detail in the technical advisory board, regardless of the fact that it is generally very easy in Germany to bring a device onto the market that can be used for therapeutic purposes. All that is required is a so-called CE classification or a CE mark.
After discussing this study, the technical advisory board unanimously decided that the German Tinnitus League therefore does not currently actively recommend participation in the study for this device under the conditions mentioned above, nor will it call for the device to be purchased.
From the standpoint of self-help advocacy, studies should not be supported in which test subjects have to pay to participate in the study or have to purchase equipment.
Prof. Dr. Gerhard Hesse, spokesman for the technical advisory board of the German Tinnitus League e. V., Prof. Dr. Gerhard Goebel, first deputy spokesman of the technical advisory board of the German Tinnitus League e. V.
Wuppertal, May 2021
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