An electroencephalography-based database to study the effects of acoustic therapies in the treatment of tinnitus

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Tinnitus is a multifactorial and heterogeneous condition that is strongly associated with hearing loss (HL), age, gender, marital status, education, and even employment. In addition, many tinnitus sufferers (approximately 65%) eventually suffer from sleep disorders, emotional and cognitive distress (e.g., stress, anxiety, or depression), or other psychological conditions1. In fact, around 70% of tinnitus cases are preceded by a mental disorder. Patients with very distressing tinnitus may also have cardiovascular, endocrine, or metabolic diseases2.

Tinnitus is a heterogeneous disease with no effective standard treatment. A recent study3 Based on a survey of 5,017 tinnitus sufferers conducted by the Tinnitus Hub web platform, seven of the 25 most commonly used treatments were sound-based therapies. From the most commonly used to the least used therapies, these were: 1St own sound stimulation, 6th masker, 11th Tinnitus Retraining Therapy (TRT), 18th Notch music, 19th sound cure, 20th acoustic neuromodulation and 21St neuromonic. As can be seen, almost a third of the currently available treatments for tinnitus depend on the effect of sound on bodily function. It is well known that noise induces physiological, cognitive and psychological changes4. However, it is still unknown how noise-based treatment can alleviate or alleviate tinnitus and what therapy is the appropriate therapy for each clinical case due to its heterogeneous nature.

Electroencephalographic (EEG) monitoring has been proposed to measure the sound effect of acoustic therapies on tinnitus. in the5the authors presented an overview of computational methods for analyzing EEG signals to assess the sound effects of acoustic therapies at the cortical level. In the past two years, the following acoustic therapies were evaluated: (1) neuromodulation, (2) auditory residual inhibition, (3) binaural beats therapy (BBT), and (4) auditory discrimination therapy (ADT). In the first case6, neuromodulation therapy was applied for 75 days, and EEG monitoring was performed every two weeks. It was found that the level of EEG connectivity decreased significantly. In the second case, residual auditory inhibition did not significantly reduce tinnitus loudness, and this finding was supported by EEG evidence as band power increased in magnitude in alpha and gamma7. Similarly, alpha band power in auditory ranges increased during residual auditory inhibition in the study conducted in8th. In the third case, BBT reduced stress (23% of patients) and tinnitus perception (15% of patients) and slightly reduced EEG synchronicity over the right frontal lobe9. In the latter case, the degree of EEG synchrony due to auditory processing decreased due to the attentional redirection achieved by ADT10.

As indicated by previous studies, EEG analysis is a helpful tool for assessing the sound effects of acoustic therapies, alongside psychoacoustic and clinical assessments. Therefore, the present database provides demographic, clinical, psychometric, and EEG information from 89 tinnitus patients who were randomly treated with one of five acoustic therapies for eight weeks. These were (1) relaxation music (placebo), (2) tinnitus retraining therapy (TRT), (3) ADT, (4) enriched acoustic environment (EAE), and (5) BBT. TRT tries to reduce tinnitus by reducing the loudness perception of the unreal sound11:12. ADT intends to draw the patient’s attention to therapy by presenting a composite sound of standard and deviant pulses in a randomized manner, thereby reducing tinnitus perception13. EAE intends to prevent HL and subsequent plastic changes in the tonotopic cortical map after acoustic trauma. EAE is based on a series of random frequency tones with an amplitude proportional to the HL reported on the patient’s audiometry14. BBT consists of two pure tones presented at each ear with a frequency difference corresponding to the oscillating EEG target band. Use of this therapy has reported a reduction in stress levels by decreasing activation of areas in the sympathetic systemfifteen, which in turn reduces the perception of tinnitus. In addition to the 89 tinnitus patients, 14 healthy volunteers were recruited, exposed to relaxing music (like the control group) and subjected to the same experimental procedure as tinnitus patients.

In total, the database contains four types of information sources from 103 participants. See Table 1. First, iemographic information refers to place of residence, gender, age (over 18 years) and nationality. Second, cclinical history includes HL level and frequency, laterality and intensity of tinnitus perception. Finally, psychometric and EEG monitoring of acoustic therapies is also included. It is important to note that the initial cohort consisted of 108 participants, of whom 103 entered the study and 71 of whom completed the experimental procedure. See fig. 1.

Table 1 Total number of participants and their corresponding study group.
Fig. 1

Flowchart based on the Consolidated Standards of Reporting Trials. A total of 108 participants were recruited, 103 of whom accepted to participate in the study and 71 of whom completed the experimental procedure.

Psychometric Monitoring was based on the Spanish version of the Hospital Anxiety and Depression Stress (HADS) and the Tinnitus Handicap Inventory (THI), which provided the psychoacoustic effects of acoustic therapies. On the one hand, the HADS questionnaire assesses the impact of tinnitus on anxiety and depression16. On the other hand, the THI questionnaire measures the level of tinnitus perception; emotional, physical and social response to tinnitus; and tinnitus intrusiveness at audition17. Further details on the questionnaire-based monitoring of this study protocol can be found in18.

EEG information gives an insight into neuroplastic changes (if any) of acoustic therapies. The available EEG data sets enable signal analysis in three modes: spontaneous, evoked and induced EEG activity. In most previous studies, only spontaneous activity was analyzed, meaning the participants were either at rest or listening to their acoustic therapy. However, EEG signals provide deeper neural information when related to specific motor, emotional, sensory, perceptual, and/or cognitive events. This relates to evoked and induced EEG activity. Traditional patterns for evoked and induced EEG activity are event-related potentials and event-related (de-)synchronization, which can be estimated from the present database. Spontaneous activity analysis helps evaluate the type of ongoing activity. In contrast, analysis of evoked and induced activity enables the study of brain responses when individuals perceive the sound, pay attention to the stimulus, make a decision, and act accordingly. In short, both bottom-up and top-down mechanisms associated with neuroplastic changes due to acoustic rehabilitation can be studied using the present database.

The present database was created according to a protocol previously approved by the Ethics Committee of the National School of Medicine of the Tecnologico de Monterrey and described and published in19, and registered under the test number: ISRCTN14553550. The database is available at20.

The study protocol was performed as follows. All participants were informed of the experimental procedure and signed an informed consent form in which they consented to the publication of their collected data and the results of their follow-up examinations. Most of the patients were recruited from the National Rehabilitation Institute and they were also informed that their chief physician was also following up the study. Chief physicians provided patient histories and demographic information.

All patients who agreed to participate in the study were assigned to one of five groups: (1) TRT, (2) EAE, (3) ADT, (4) BBT, and (5) placebo. Patients without severe HL were randomized to placebo and EAE groups. On the other hand, patients with a well-identified tinnitus pitch were enrolled in TRT or ADT groups. Patients with tinnitus below 1 kHz were assigned to BBT. The control group (healthy volunteers) were asked to use the same relaxation music as the placebo group. On average, 17 volunteers were used per group (see Table 1). Note that each acoustic therapy was adjusted for HL level, tinnitus frequency, and tinnitus intensity, apart from the relaxing music, which was used as a placebo.

All participants (both with and without tinnitus) were instructed to use the appropriate acoustic therapy for one hour a day, any time of the day, for eight weeks. Therapy was monitored four times during the two months: the first (session 1), the third (session 2), the fifth (session 3) and the eighth (session 4) weeks after the start of therapy. At each monitoring session, the THI and HADS questionnaires were applied and an EEG recording was performed as shown in Fig. 2. From Fig. 1 it can be seen that only 71 of the 103 participants completed the experimental procedure. Although the repository contains 103 files, not all of them are complete. This information is given in the Excel file found in20.

Fig. 2
figure 2

study design. The present database contains (1) demographic information, (2) clinical history, and (3) psychometric and (4) EEG monitoring of 103 volunteers, 89 of whom suffered from tinnitus and the remainder were controls.

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