Tinnitus suppression in patients with cochlear implants

The effect of cochlear implantation on tinnitus in patients with post lingual bilateral profound hearing loss

INTRODUCTION

In this study we investigated the effect of cochlear implantation on tinnitus in patients with post lingual bilateral profound hearing loss.

METHODS

In this retrospective study, 66 post-lingual deaf patients over 18 years old who referred for cochlear implantation and complained of tinnitus were included. Patients were divided into two groups with residual hearing (in frequency 250-500 Hz) and without residual hearing. All data including age, gender, type of implants, type of surgery, cause of the disease, and information on the THI score before cochlear implantation, one month after cochlear implantation and one year after cochlear implantation was recorded and analyzed.

RESULTS

Nine patients had residual hearing, while 57 patients did not. After one month and one year, in both groups, the mean THI score has decreased significantly (p-value = 0.001), but there was no significant difference in the mean THI score before surgery and one month and one year after surgery between two groups with and without residual hearing. There was no significant difference in tinnitus severity according to THI-grade between two groups. Also there was no significant difference in THI score and the cause of the hearing loss, type and insertion method of implantation, one month and one year after the surgery between two groups.

CONCLUSION

According to our results, the was no significant correlation between residual hearing and tinnitus score before surgery, one month and one year after the surgery.

Changes in Tinnitus Characteristics and Residual Inhibition following Cochlear Implantation: A Prospective Analysis

This study aims to explore the effect of cochlear implantation on tinnitus perception. A prospective study was conducted on 72 adult hearing-impaired patients to evaluate tinnitus perception before and after cochlear implantation, using standardized tinnitus questionnaires (the tinnitus sample case-history questionnaire, tinnitus functional index (TFI), and tinnitus handicap inventory (THI)). A large variety of demographic and hearing- and implant-related data was collected from patient hospital records to explore possible associations with the implantation effect. The prevalence of tinnitus complaints before implantation was 58.3%. The temporary induction or aggravation of tinnitus immediately after surgery was noted in 20% and 46.7% of patients, respectively. When evaluated 3 months after implantation, 60% of tinnitus patients experienced a clinically significant reduction in their complaints; most of the improvements were experienced immediately after activation of the implant. Only the scores for TFI and THI at baseline were found to be significantly correlated with a reduction in TFI scores after implantation. In 80% of tinnitus patients, the tinnitus remained suppressed for some time after taking off the device. The large subset of patients with residual inhibition supports the involvement of central pathophysiological processes in implantation effects on tinnitus, which are explored in this paper.

Experience of tinnitus in adults who have severe-to-profound hearing loss: A scoping review

Background

Tinnitus is defined as the subjective perception of sound in the absence of an external stimulus, and tinnitus disorder becomes relevant when it is associated with emotional distress, cognitive dysfunction, and/or autonomic arousal. Hearing loss is recognized as the main risk factor for the pathogenesis of tinnitus. However, clinical guidelines for tinnitus disorder provide little direction for those who have severe-to-profound hearing loss including those who are pre-lingually Deaf. The aim of this scoping review was to catalogue what is known from the existing literature regarding the experience and management of tinnitus in adults who have a severe-to-profound hearing loss.

Summary

A scoping review was conducted following the Preferred Reporting Item for Systematic Reviews and Meta-analysis extension for Scoping Reviews. Records were included if they reported an evaluation of tinnitus in adults who had severe-to-profound hearing loss. The online databases Ovid (MEDLINE, EMBASE and PsycINFO), CINAHL, ProQuest, Scopus, and Google Scholar were searched using the search terms ‘tinnitus’ (as a MESH term) and ‘deaf’ OR ‘profound hearing loss. Thirty-five records met the inclusion criteria for this review and were cataloged according to three major themes: Impact of tinnitus in deaf adults; Primary treatment of tinnitus in deaf adults; and Cochlear implant studies where tinnitus was a secondary outcome. Tinnitus symptom severity was assessed before and after intervention using tinnitus validated questionnaires in 29 records, with six further records using other assessment tools to measure tinnitus severity. Participants using cochlear implants were included in 30 studies. Medication, repetitive transcranial magnetic stimulation (rTMS), electrical promontory stimulation, and behavioral self-control therapy were each reported in single records.

Key messages

This scoping review cataloged the experience, assessment, and treatment of tinnitus in adults who have severe-to-profound hearing loss. It is shown that there is very limited research reported in this field. Although this review included many records, most focused on the provision of cochlear implants for severe-to-profound hearing loss, with assessment and measurement of tinnitus as a baseline or secondary outcome. Largely missing in the literature are empirical studies that seek firstly to understand the nature of the experience of tinnitus by people with no or little residual access to external sound.

Experience of adult cochlear implantation at a tertiary hospital

BACKGROUND

The prevalence of adult cochlear implant (CI) surgery is increasing. However, the relevant adult CI data in Taiwan are insufficient due to the relatively small number of adult implant patients. The two main factors hindering adult implantation are the high cost of the surgery itself and inadequate knowledge regarding the effectiveness of CI for hearing and suppression of tinnitus. Here, we present data regarding adult CI outcomes from a single tertiary hospital.

METHODS

A total of 116 consecutive adult CI recipients (≥18 years old) who completed at least 12 months of speech perception tests (words and sentences) between January 1999 and December 2020 were enrolled in this retrospective population-based cohort study. Thirty patients completed speech perception (words and sentences) testing as well as three questionnaires relating to quality of life, and 71 completed full tinnitus suppression studies. Subjects' pre- and post-CI questionnaires were evaluated to assess overall CI outcome.

RESULTS

For auditory evaluation, the scores of easy sentences (ES), difficult sentences (DS), and phonetically balanced (PB) word recognition tests reached a plateau at 3 months post-CI (p = 0.005, 0.001, and 0.004, respectively) in most subjects. The post-CI scores of bodily pain, mental health, and social role functioning were significantly higher than corresponding pre-CI scores on the SF-36 Health Survey-Taiwan version (p = 0.036, 0.019, and 0.002, respectively). Furthermore, the post-CI scores of basic sound perception, speech production, and advanced sound perception were significantly higher than the corresponding pre-CI scores on the Nijmegen Cochlear Implant Questionnaire (p < 0.001, 0.013, and <0.001, respectively). Self-esteem was significantly correlated with the Categories of Auditory Performance scale and Speech Intelligibility Rating scale at 3, 6, and 9 months post-CI. CI improved tinnitus in approximately 65.1% of 71 adults. Based on the Tinnitus Handicap Inventory, 66.7% of patients were in grade 3-5 before surgery. However, after CI, only 34.4% of patients remained in THI grade 3-5.

CONCLUSION

This study confirmed that CI can improve speech perception (words and sentences), physical health, mental health, social interaction, and self-esteem in adult patients with profound hearing loss. CI also significantly alleviated tinnitus. The outcomes of ES, DS, and PB tests at 3 months post-CI were non-inferior to other longer post-CI periods and could be utilized as references for recovery and evaluation of prognosis.

Review of Speech Outcomes in Cochlear Implant Recipients at a Nascent Cochlear Implant Program

Introduction: The use of cochlear implantation to rehabilitate moderate to profound sensorineural hearing loss has become more widespread; however, the adult utilization rate of cochlear implant candidates is still very less. The study aims to examine the percentage of adult patients in a heterogeneous group of cochlear implant recipients at a nascent cochlear implant program who demonstrate improvements in speech outcomes.

Methods: Speech outcome scores were assessed preoperatively and postoperatively at three, six, and 12-month intervals using consonant-nucleus-consonant (CNC) words and AzBio sentences in quiet. Mean speech outcome scores at each time point and binomial distribution tables with 95% CI were used to assess individual improvement in speech understanding.

Results: 45 patients underwent a total of 49 cochlear implantation surgeries. The mean age at surgery was 62 years. The mean preoperative CNC score in the ear to be implanted was 18%±18, while the mean postoperative CNC score at three, six, and 12 months was 35%±21, 44%±23, and 45%±25, respectively. The mean preoperative AzBio score in the ear to be implanted was 22%±26 while the mean postoperative AzBio score at three, six, and 12 months was 50%±29, 56%±27, and 63%±26, respectively. Of the implantations, 74% (32 of 43) and 69% (22 of 32) showed significant improvement at six months or one year using AzBio and CNC binomial distribution tables, respectively.

Conclusions: Findings demonstrate significant improvements in speech perception following cochlear implantation for patients not benefiting from hearing aid aural rehabilitation. The study provides realistic expectations for new and emerging programs hoping to demonstrate cochlear implant utility for improving patients’ speech outcomes.

What Makes Tinnitus Loud?

INTRODUCTION

Tinnitus loudness is a subjective measure, and it does not directly reflect either tinnitus severity or the impact on daily life. Nevertheless, loud tinnitus may be the most frequent clinical complaint of tinnitus patients. Factors contributing to the loudness of the phantom sound have rarely been studied. We evaluated both matched and self-rated loudness in a large sample of patients with tinnitus and analyzed the influencing factors among demographic, hearing, and tinnitus characteristics.

METHODS

Two hundred ninety-nine patients with chronic tinnitus were enrolled. We evaluated the matched loudness, minimal masking level (MML), and visual analog scale (VAS) loudness. Stepwise multiple regression analyses were performed for each loudness measure using independent variables of age, sex, time since tinnitus onset, tinnitus laterality, pure-tone average, tinnitus pitch, tinnitus handicap inventory (THI) score, VAS annoyance, disturbance and daily tinnitus duration, and depression score. We calculated bivariate correlations between each loudness measure and all independent variables.

RESULTS

The psychoacoustic loudness measures (matched loudness and MML) were highly correlated and were affected by the hearing deficit and tinnitus pitch (Pearson r > 0.5 for pure tone averages, and r > 0.3 for tinnitus pitch for both variables, p < 0.05), whereas the subjective measurement (VAS loudness) exhibited little to no correlation with the other two measures and was related to psycho-emotional factors such as the THI score, VAS variables, and depression (Pearson r > 0.6 for VAS annoyance, r > 0.4 for VAS daily duration and disturbance and THI score, r > 0.3 for the depression score, p < 0.05).

CONCLUSION

The matched tinnitus loudness and MML values were influenced principally by the extent of hearing loss and related factors, suggesting that rehabilitation using hearing aids could help reduce perception of tinnitus loudness. A psycho-emotional approach might more effectively lessen self-perceived loudness.

Cochlear Implantation in Meniere's Disease: A Systematic Review and Meta-Analysis

OBJECTIVES/HYPOTHESIS

Meniere's disease (MD) is a debilitating condition characterized by hearing loss, vertigo, and tinnitus. The objective of this study was to systematically investigate outcomes in MD after cochlear implantation (CoI), with and without labyrinthectomy.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

A systematic review of articles in Medline and Embase was performed to identify all studies of patients with MD who underwent CoI. This analysis evaluates outcomes of speech recognition, pure tone audiometry, vertigo, tinnitus, and quality of life.

RESULTS

Of 321 studies identified, 37 were included, involving 216 patients. Mean age at implantation was 61.4 years (range 27-85 years) with average length of follow-up at 1.7 years (range 0-9 years). Forty-four (20.4%) patients underwent labyrinthectomy. Meta-analysis demonstrated significant improvements in audiometric outcomes following CoI. There was a statistically significant improvement in Hearing in Noise Test performance, with a mean difference improvement of 44.7 (95% confidence interval [CI] [8.8, 80.6]) at 6 months and 60.1 (95% CI [35.3, 85.0]) at 12 months. The Freiburger Monosyllabic Test (FMT) and Consonant-Nucleus-Consonant (CNC) also improved significantly, with mean difference improvements of 46.2 (95% CI [30.0, 62.4]) for FMT and 19.3 (95% CI [8.1, 30.4]) for CNC. There was a statistically significant decrease in tinnitus, as measured by a mean difference reduction of 48.1 (95% CI [1.0, 95.2]) in the Tinnitus Handicap Index.

CONCLUSIONS

CoI with and without simultaneous labyrinthectomy is a viable treatment option for patients with MD, yielding high rates of tinnitus suppression and vertigo control. Post-CoI MD patients demonstrate similar postoperative speech perception outcomes to non-MD implant recipients. Laryngoscope, 131:1845-1854, 2021.

Cochlear implantation for patients with tinnitus - A systematic review

BACKGROUND

Cochlear implantation (CI) is used in patients with severe-to-profound hearing loss when hearing aids provide limited or no benefit for speech perception. Studies on this topic reported tinnitus reduction as a common side effect of the electrical activation after cochlear implantation. So far, it is unclear what the effect is when patients do receive their implant primarily because of tinnitus complaints.

OBJECTIVES

To assess the effectiveness of the electrical stimulation with a cochlear implant in patients with tinnitus as a primary complaint, by systematically reviewing the literature.

METHODS

Two independent authors identified studies, extracted data and assessed risk of bias of included studies. Original studies reporting outcomes of electrical stimulation by cochlear implantation for primarily tinnitus (defined as severe or incapacitating distress levels) were included, if they reported a follow-up of at least three months. The pre- and post-implantation tinnitus distress scores on single and/or multi-item questionnaires of the included studies were extracted.

RESULTS

In total, 4091 unique articles were retrieved. After screening titles, abstracts and full texts, we included seven prospective cohort studies (105 subjects in total, range: 10-26). All studies had considerable risks of bias. All tinnitus patients in the included studies had asymmetrical hearing loss or single-sided deafness. A statistically significant tinnitus distress improvement based on tinnitus questionnaire scores was found in every study.

CONCLUSION

Our systematic review reveals that electrical stimulation by cochlear implants in patients with a primary complaint of tinnitus has a positive impact on tinnitus distress. Nevertheless, only small sample sizes were found and studies showed considerable risks of bias.^a.

Effects of Cochlear Implantation on Tinnitus and Depression

INTRODUCTION

Tinnitus is prevalent in 66-88% of cochlear implant users. The reason for this high prevalence is that hearing impairment is the most common cause of tinnitus.

OBJECTIVE

This study aims to determine the effect of cochlear implant and to compare the severity of tinnitus and depression in adult cochlear implant users with tinnitus.

METHODS

Patients diagnosed with tinnitus filled out the Tinnitus Handicap Inventory and the Beck Depression Inventory during CI candidate evaluation. The audiological follow-up in the present study included only patients suffering from tinnitus before the cochlear implant surgery. This study included only patients who had tinnitus handicap inventory and Beck Depression Inventory clinical records pre- and postoperatively, including 23 adult cochlear implant users (13 males and 10 females) aged 18-76 years.

RESULTS AND CONCLUSION

There was a statistically significant decrease in the severity of tinnitus and depression after cochlear implant. As the participants' tinnitus level and grade decreased, their depression levels also decreased. Depression levels decreased after the use of a cochlear implant compared to before cochlear implantation. Cochlear implantation is currently used only for hearing restoration. However, cochlear implantation may be used in rehabilitation for tinnitus in patients with severe hearing loss and in tinnitus patients. In addition cochlear implantation can be a depression rehabilitation method by reducing tinnitus.

Effects of Vibrant Soundbridge on tinnitus accompanied by sensorineural hearing loss

OBJECTIVES

Tinnitus is a common symptom among patients with hearing loss, and many studies have reported successful tinnitus suppression with hearing devices. Active middle ear implantation of the Vibrant Soundbridge (VSB) is a good alternative to existing hearing devices. This study evaluated the effects of VSB implantation on tinnitus and sought to identify the main audiological factor that affects tinnitus suppression.

METHODS

The study participants were 16 adults who had tinnitus with sensorineural hearing loss, and who underwent VSB implantations. Pure-tone audiometry; word recognition test; tinnitus handicap inventory (THI); and visual analog scale (VAS) assessment of loudness, awareness, and annoyance were performed before and 12 months after surgery. Changes in hearing threshold, word recognition scores (WRS), THI scores, and VAS scores were analyzed.

RESULTS

VAS scores for loudness (mean difference: 1.9, 95% CI: 0.6, 3.1), awareness (mean difference: 1.6, 95% CI: 0.4, 2.8), and annoyance (mean difference: 1.7, 95% CI: 0.7, 2.8) showed significant improvements from baseline to 12 months after surgery. In addition, THI scores showed a significant decrease (mean difference: 13.8, 95% CI: 2.9, 24.9). The average hearing threshold level, WRS, and most comfortable level (MCL) also showed significant improvements at 12 months after surgery (mean difference: 17.3, 95% CI: 13.3, 21.3; mean difference: -7.6, 95% CI: -15.1, -0.1; mean difference: 26.3, 95% CI: 22.9, 29.6, respectively). Among the aforementioned factors, changes in MCL were best correlated with those in THI scores (mean difference: 2.55, 95% CI: 0.90, 4.21).

CONCLUSION

A VSB implant is beneficial to subjects with tinnitus accompanied by sensorineural hearing loss. The changes in THI scores best correlated with those in MCL. This improvement may represent a masking effect that contributes to tinnitus suppression in patients with VSB implants.

A Cross-Sectional Questionnaire Study of Tinnitus Awareness and Impact in a Population of Adult Cochlear Implant Users

Supplemental Digital Content is available in the text.

Objectives:

The primary aim was to identify the proportion of individuals within the adult cochlear implant population who are aware of tinnitus and those who report a negative impact from this perception, using a bespoke questionnaire designed to limit bias. A secondary aim was to use qualitative analysis of open-text responses to identify themes linked to tinnitus perception in this population.

Design:

A cross-sectional questionnaire study of a large clinical population who received an implant from Cambridge University Hospitals, United Kingdom.

Results:

Seventy-five percent of respondents reported tinnitus awareness. When impact scores for six areas of difficulty were ranked, 13% of individuals ranked tinnitus their primary concern and nearly a third ranked tinnitus in the top two positions. Tinnitus impact was not found to reduce with duration since implantation. The most common open-text responses were linked to a general improvement postimplantation and acute tinnitus alleviation specific to times when the device was in use.

Conclusions:

Tinnitus is a problem for a significant proportion of individuals with a cochlear implant. Clinicians, scientists, and cochlear implant manufacturers should be aware that management of tinnitus may be a greater priority for an implantee than difficulties linked to speech perception. Where a positive effect of implantation was reported, there was greater evidence for masking of tinnitus via the implant rather than reversal of maladaptive plasticity.

A Prospective Study of the Effect of Cochlear Implantation on Tinnitus

Previous studies have shown diverse and sometimes even contrary results concerning the effect of cochlear implantation on tinnitus and the factors that can influence this effect. The aim of this prospective questionnaire study was to determine the effects of cochlear implantation on tinnitus and explore which factors can influence the effect of cochlear implantation on tinnitus. Forty-four of the patients implanted in our hospital returned 2 questionnaire packages, i.e., one before the cochlear implantation and one 6 months after implantation. Before implantation, 66% of the patients experienced tinnitus. This study shows that cochlear implantation could help to reduce tinnitus and the tinnitus handicap in at least 28% of the patients with preoperative tinnitus. In 72% of the patients the tinnitus remained after implantation. None of the patients developed tinnitus after implantation. A shorter duration of tinnitus prior to implantation, a more fluctuating type of tinnitus, a higher tinnitus handicap prior to implantation, and a round-window surgical approach might have a positive influence on the effect of cochlear implantation on tinnitus, but further research is necessary to confirm these findings.

A Quantitative Electroencephalography Study on Cochlear Implant-Induced Cortical Changes in Single-Sided Deafness with Tinnitus

The mechanism of tinnitus suppression after cochlear implantation (CI) in single-sided deafness (SSD) is not fully understood. In this regard, by comparing pre- and post-CI quantitative electroencephalography (qEEG), we explored cortical changes relevant to tinnitus improvement. In SSD patients who underwent CI, qEEG data were collected: (1) before CI, (2) 6 months post-operatively with CI-on, and (3) 30 min after CI-off and source-localized cortical activity/functional connectivity analyses were performed. Compared to the pre-operative baseline, the CI-on condition demonstrated significantly decreased activity in the right auditory- and orbitofrontal cortices (OFC) for the delta frequency band as well as decreased connectivity between the auditory cortex/posterior cingulate cortex for the delta/beta2 bands. Meanwhile, compared to the CI-off condition, the CI-on condition displayed decreased activity in the right auditory cortices/OFC for the delta band, and in bilateral auditory cortices, left inferior frontal cortex/OFC for the gamma band. However, qEEG analyses showed no significant differences between the CI-off and baseline conditions. CI induced overall decreased cortical activity and functional connectivity. However, judging from no differences between the CI-off and baseline conditions, CI-induced cortical activity and functional connectivity changes are not by cortical plastic changes, but by dynamic peripheral reafferentation.

Developing an assessment approach for perceptual changes to tinnitus sound characteristics for adult cochlear implant recipients

OBJECTIVE

To investigate the impact of cochlear implantation on tinnitus suppression, characteristics, localization, and duration.

DESIGN

A cochlear implant (CI) recipient-focused postal questionnaire survey.

STUDY SAMPLE

The questionnaire was posted, with consent, to 100 adults who had received a unilateral CI at the RNTNEH between 1988 and 1999. All adults spoke English as their first language and were postlingually deafened. Sixty-eight adults (38 female, 29 male, one unspecified) aged 31-80 years (mean 61 years) completed and returned the questionnaire without interview.

RESULTS

With the processor 'ON', CI recipients experienced total or partial suppression of tinnitus ipsilateral to their CI in 57% of cases, and in 43% where tinnitus was perceived contralateral to the CI. The percentage of CI recipients who experienced high tone tinnitus was reduced from 60% pre-implant to 29% post-implant with the processor 'ON' while pulsatile tinnitus was reduced from 38% pre-implant to 13% post-implant. CIs were also found to reduce the tonal complexity and duration, and change the source localization of tinnitus post-implantation.

CONCLUSIONS

Perceptual changes to tinnitus can take place post-implantation. Changes can occur within the four categories explored: tinnitus suppression, characteristics, localization, and duration of awareness per day.

[Cochlear implants and tinnitus]

The cochlear implant became a very successful method of hearing rehabilitation for patients with profound sensorineural hearing loss. The benefits of the CI extend beyond the medical success and positively influence social and psychosocial areas, reflected by an improved HRQoL. Furthermore, variety of studies demonstrated that the tinnitus severity improves in 46-95 % of cases following the cochlear implantation. However, the parameters investigated in such studies are not always standardized or addressed by validated questionnaires, which explains the high outcome variation between the studies. The relationships between HRQoL and tinnitus distress before and after cochlear implantation have not been well studied. Nevertheless, it is believed that the improvement in HRQoL following CI affects particularly tinnitus.However, an existing tinnitus can also worsen or occur for the first time after the surgery. Since neither tinnitus frequency nor tinnitus loudness correlate with the tinnitus-induced distress, the measurement of HRQoL, distress factors, stress reactions and psychiatric comorbidities appears to be the meaningful assessment of positive or negative effects of CI on tinnitus.Initial studies demonstrated that also patients with unilateral hearing loss may benefit from CI supply, as shown by an improvement in HRQoL and reduction of tinnitus-induced distress. For those patients, who despite CI implantation experience severe tinnitus, there is an option of tinnitus-specific CI-fitting and tinnitus-specific therapy with psychosomatic and psychological approaches, and- in addition- a treatment of possible mental comorbidities.

Suppression of Tinnitus in Chinese Patients Receiving Regular Cochlear Implant Programming

Objective:

To assess the clinical effect of cochlear implant programming on tinnitus.

Methods:

Tinnitus patients (n = 234) were divided into 3 groups: (1) preoperative tinnitus (n = 108), (2) postoperative tinnitus occurring before implant switch-on at week 4 (n = 88), and (3) tinnitus occurring more than 1 year postoperatively (n = 44). Patients in each group were randomly allocated into a programming subgroup that received programming for 12 weeks postoperatively or after tinnitus occurrence or a control subgroup. Impedance testing and the Tinnitus Handicap Inventory (THI) were performed preoperatively and at 4, 6, 8, and 12 weeks postoperatively (groups 1 and 2) or after tinnitus occurrence (group 3). Comparisons were performed using t tests and chi-square tests.

Results:

Impedance was significantly lower in the programming subgroup than in the control subgroup in groups 1 and 2 at 8 and 12 weeks and in group 3 at 12 weeks. The THI scores decreased in both programming and control subgroups in all groups. However, this decrease was pronounced in the programming subgroup, whereas in the control subgroup, it occurred slowly over time.

Conclusion:

Cochlear implant programming decreases impedance and improves tinnitus symptoms.

Tinnitus Suppression by Intracochlear Electrical Stimulation in Single-Sided Deafness: A Prospective Clinical Trial - Part I

Cochlear implantation is a viable treatment option for tinnitus, but the underlying mechanism is yet unclear. Is the tinnitus suppression due to the reversal of the assumed maladaptive neuroplasticity or is it the shift in attention from the tinnitus to environmental sounds and therefore a reduced awareness that reduces tinnitus perception? In this prospective trial, 10 patients with single-sided deafness were fitted with a cochlear implant to investigate the effect of looped intracochlear electrical stimulation (i.e. stimulation that does not encode environmental sounds) on tinnitus, in an effort to find optimal stimulation parameters. Variables under investigation were: amplitude (perceived stimulus loudness), anatomical location inside the cochlea (electrode/electrodes), amplitude modulation, polarity (cathodic/anodic first biphasic stimulation) and stimulation rate. The results suggest that tinnitus can be reduced with looped electrical stimulation, in some cases even with inaudible stimuli. The optimal stimuli for tinnitus suppression appear to be subject specific. However, medium-to-loud stimuli suppress tinnitus significantly better than soft stimuli, which partly can be explained by the masking effect. Although the long-term effects on tinnitus would still have to be investigated and will be described in part II, intracochlear electrical stimulation seems a potential treatment option for tinnitus in this population.

Tinnitus suppression by electric stimulation of the auditory nerve

Electric stimulation of the auditory nerve via a cochlear implant (CI) has been observed to suppress tinnitus, but parameters of an effective electric stimulus remain unexplored. Here we used CI research processors to systematically vary pulse rate, electrode place, and current amplitude of electric stimuli, and measure their effects on tinnitus loudness and stimulus loudness as a function of stimulus duration. Thirteen tinnitus subjects who used CIs were tested, with nine (70%) being "Responders" who achieved greater than 30% tinnitus loudness reduction in response to at least one stimulation condition and the remaining four (30%) being "Non-Responders" who had less than 30% tinnitus loudness reduction in response to any stimulus condition tested. Despite large individual variability, several interesting observations were made between stimulation parameters, tinnitus characteristics, and tinnitus suppression. If a subject's tinnitus was suppressed by one stimulus, then it was more likely to be suppressed by another stimulus. If the tinnitus contained a "pulsating" component, then it would be more likely suppressed by a given combination of stimulus parameters than tinnitus without these components. There was also a disassociation between the subjects' clinical speech processor and our research processor in terms of their effectiveness in tinnitus suppression. Finally, an interesting dichotomy was observed between loudness adaptation to electric stimuli and their effects on tinnitus loudness, with the Responders exhibiting higher degrees of loudness adaptation than the Non-Responders. Although the mechanisms underlying these observations remain to be resolved, their clinical implications are clear. When using a CI to manage tinnitus, the clinical processor that is optimized for speech perception needs to be customized for optimal tinnitus suppression.

Adaptation and maladaptation insights from brain plasticity

Evolutionary concepts such as adaptation and maladaptation have been used by neuroscientists to explain brain properties and mechanisms. In particular, one of the most compelling characteristics of the brain, known as neuroplasticity, denotes the ability of the brain to continuously adapt its functional and structural organization to changing requirements. Although brain plasticity has evolved to favor adaptation, there are cases in which the same mechanisms underlying adaptive plasticity can turn into maladaptive changes. Here, we will consider brain plasticity and its functional and structural consequences from an evolutionary perspective, discussing cases of adaptive and maladaptive plasticity and using examples from typical and atypical development.

Changes in the tinnitus handicap questionnaire after cochlear implantation

PURPOSE

To determine (a) changes in the Tinnitus Handicap Questionnaire (THQ) for patients using cochlear implants, (b) differences between patients who receive total or partial relief, and (c) identifiable characteristics of those who report tinnitus after implantation.

METHOD

Pre- and postoperatively, 244 adults were administered the THQ when they reported tinnitus.

RESULTS

Of the 153 patients who had tinnitus preoperatively, 94 (61%) patients reported total suppression and 59 (39%) reported a partial reduction. In 91 patients who did not have tinnitus before implantation, 11 (12%) reported tinnitus postimplantation. The THQ score decreased from 41% preimplant to 30% postimplant. The largest reductions involved social handicap and hearing. Patients with a more severe hearing loss might be more likely to experience an exacerbation of their tinnitus. We were not able to clearly identify differences between patients who received total or partial relief and the characteristics of patients who reported tinnitus after implantation. Those who acquired tinnitus had the shortest duration hearing loss (5.6 years) and were the oldest (63 years). The average THQ score of patients getting tinnitus was 29%.

CONCLUSIONS

Most tinnitus patients benefit from receiving a cochlear implant.

Tinnitus and cochlear implantation

Tinnitus is a common experience, but there is very marked heterogeneity of aetiology, perception and the extent of distress among individuals who experience tinnitus. In view of this, a modern approach to tinnitus should consider homogeneous groups of individuals. This review considers tinnitus experiences in patients undergoing cochlear implantation, this being of interest because the prevalence of tinnitus in this patient group prior to surgery may shed some light on the link between cochlear dysfunction and tinnitus Second, any change in tinnitus experience as a result of electrode placement surgery or cochlear implant activation has relevance for patient counselling and informed consent. Finally, in recent tinnitus retraining therapy literature there has been the suggestion that unilateral sound therapy for tinnitus patients may set up an unhelpful asymmetry of input to the auditory system, with possible exacerbation of contralateral tinnitus. Unilateral cochlear implant use represents the most dramatic asymmetry possible and hence is a test of that hypothesis. Relevant papers (n = 32) were identified from literature databases. The standard of reporting tinnitus results was inconsistent. Tinnitus is experienced by up to 86% of adult cochlear implant candidates, but is not universal and is only troublesome in a small proportion (reported as 27% in one study). Electrode insertion may induce tinnitus in a small (up to 4%) number of patients, but this is rare. Cochlear implant device use is associated with reduction of tinnitus intensity and awareness in up to 86% of patients, and rarely with exacerbation (up to 9%). There are some indications in the literature that the more complex the simulation strategy, the larger that effect. Specifically, unilateral cochlear implant use was generally associated with reduction of contralateral tinnitus (in up to 67% of individuals) rather than exacerbation, and so the assertion that unilateral sound therapy for tinnitus is contraindicated is not proven.

Stimulation by cochlear implant in unilaterally deaf rats reverses the decrease of inhibitory transmission in the inferior colliculus

In the last decade, numerous studies have investigated synaptic transmission changes in various auditory nuclei after unilateral cochlear injury. However, few data are available concerning the potential effect of electrical stimulation of the deafferented auditory nerve on the inhibitory neurotransmission in these nuclei. We report here for the first time the effect of chronic electrical stimulation of the deafferented auditory nerve on alpha1 subunit of the glycinergic receptor (GlyRalpha1) and glutamic acid decarboxylase (GAD)67 expression in the central nucleus of inferior colliculus (CIC). Adult rats were unilaterally cochleectomized by intracochlear neomycin sulphate injection. Fifteen days later, the ipsilateral auditory nerve was chronically stimulated either 4, 8 or 22 h daily, for 5 days using intracochlear bipolar electrodes. GlyRalpha1 and GAD67 mRNA and protein were quantified in the CIC using in situ hybridization and immunohistofluorescence methods. Our data showed that as after surgical ablation, GlyRalpha1 and GAD67 expression were strongly decreased in the contralateral CIC after unilateral chemical cochleectomy. Most importantly, these postlesional down-modulations were significantly reversed by chronic electrical stimulation of the deafferented auditory nerve. This recovery, however, did not persist for more than 5 days after the cessation of the deafferented auditory nerve electrical stimulation. Thus, downregulations of GlyRalpha1 and GAD67 may be involved both in the increased excitability observed in the CIC after unilateral deafness and consequently in the tinnitus frequently observed in unilateral adult deaf patients. Electrical stimulation of the deafferented auditory nerve in patients may be a potential new approach for treating tinnitus with unilateral hearing loss.

Electrical Stimulation of the Cochlea to Reduce Tinnitus

This article reviews possible neural correlates of tinnitus, including an increase in rate, a decrease in rate, periodic activity, synchronous activity across neurons, and an edge between active and inactive neurons. We make some suggestions regarding how electrical current might alter these patterns of neural activity. For example, if tinnitus were represented with periodic neural activity, then electrical stimulation would need to disrupt this periodicity. Some cases of cochlear electrical stimulation are reviewed that show the tinnitus can be reduced or eliminated with cochlear electrical stimulation although it varies across individuals. Finally, after summarizing some key observations, we suggest some next steps to bring this into a clinical application.

Surgical emphysema: a rare complication following cochlear implantation

A case report of surgical emphysema following adult cochlear implantation. The clinical picture, investigations and management of this rare case will be discussed.

Tinnitus modifications after cochlear implantation

Tinnitus can be defined as a phantom sensation in the absence of an external sound. In our study, we evaluated the effect of cochlear implant on tinnitus evolution. Among adult, postlingually deaf patients who underwent cochlear implantation at our clinic, we selected 20 subjects with pre-implantation tinnitus (group A) and 10 subjects without pre-implantation tinnitus (group B). Pre- and post-surgery tinnitus was assessed through two questionnaires: the first one dealing with tinnitus characteristics and psychosocial impact, and the second one represented by THI, an internationally validated score of evaluation of the effects of tinnitus on patient's emotions and activities of daily living. None of the patients belonging to group B developed tinnitus after surgery. As for group A, 40% of patients declared suppression of tinnitus, 30% attenuation of tinnitus after surgery, 25% reported tinnitus was unchanged and 5% reported worsening of tinnitus. In the nine patients with bilateral tinnitus (45%), after implantation tinnitus disappeared from both sides in four patients and attenuated bilaterally in four patients. A comparison between pre- and post-implantation THI scores showed decreased score in 65% of cases, unchanged score in 30% and increased score in 5%. The beneficial effect of cochlear implant on tinnitus, reported by a majority of patients, could be due to acoustic masking, to direct electrical stimulation of the acoustic nerve, and above all to a possible cochlear implantation dependent reorganization of the central auditory pathways and associative cerebral areas. In the light of these results, the authors propose (1) to include tinnitus in the selection criteria of which ear to implant; (2) to consider implantation eligibility for patients with bilateral severe hearing loss associated with severe tinnitus; and (3) to inform patients about the small risk of post-operative tinnitus worsening.

Long-Term Evaluation of Treatment of Chronic, Therapeutically Refractory Tinnitus by Neurostimulation

OBJECTIVE

Long-term evaluation of treatment of chronic, therapeutically refractory tinnitus by means of chronic electrical stimulation of the vestibulocochlear nerve.

PATIENTS

Inclusion criteria were severe, chronic, therapeutically refractory, unilateral tinnitus and severe hearing loss at the ipsilateral site. Out of 6 patients, 4 patients were selected for long-term evaluation. Two patients were not evaluated because of premature dropout.

MATERIAL AND METHODS

A stimulation electrode was placed around the vestibulocochlear nerve through a retrosigmoid approach and connected to a subcutaneously positioned pulse generator via an extension cable. Follow-up was performed 3 months and 42.5 months after implantation. Three measures for treatment outcome were used. First, effect sizes were determined by means of the total Tinnitus Handicap Inventory (THI) score using Cohen's formula. Second, general and tinnitus-specific audiometric tests were performed in on and off conditions of the neurostimulation system. Third, recordings were noted for tinnitus severity and treatment success on a visual analogue scale.

RESULTS

All 4 patients reported successful treatment with neurostimulation. The effect size after 3 months was 0.7, indicating an average effect, while the effect size measured during long-term follow-up was 1.75, indicating a substantial effect with major clinical implications. No changes in hearing level for both ears were measured. The neurostimulation system did not change the tinnitus pitch in any of the patients, and resulted in a minimal reduction of tinnitus loudness in only 2 patients. In all 4 patients the original tinnitus sound was replaced by another, pleasantly perceived sound. The average VAS score of perceived tinnitus severity was reduced from 8 to 3.25. The average VAS score for treatment success was 7.25.

CONCLUSIONS

The long-term follow-up of neurostimulation treatment for chronic tinnitus shows promising results. Long-term results were better than those determined after a 3-month follow-up. In all patients the tinnitus was replaced by another sound, which was perceived as pleasant. Further studies are needed before accepting neurostimulation as a treatment modality for chronic, therapeutically refractory tinnitus.

Cochlear implants: cortical plasticity in congenital deprivation

Congenital auditory deprivation (deafness) leads to a dysfunctional intrinsic cortical microcircuitry. This chapter reviews these deficits with a particular emphasis on layer-specific activity within the primary auditory cortex. Evidence for a delay in activation of supragranular layers and reduction in activity in infragranular layers is discussed. Such deficits indicate the incompetence of the primary auditory cortex to not only properly process thalamic input and generate output within the infragranular layers, but also incorporate top-down modulations from higher order auditory cortex into the processing within primary auditory cortex. Such deficits are the consequence of a misguided postnatal development. Maturation of primary auditory cortex in deaf animals shows evidence of a developmental delay and further alterations in gross synaptic currents, spread of activation, and morphology of local field potentials recorded at the cortical surface. Additionally, degenerative changes can be observed. When hearing is initiated early in life (e.g., by chronic cochlear-implant stimulation), many of these deficits are counterbalanced. However, plasticity of the auditory cortex decreases with increasing age, so that a sensitive period for plastic adaptation can be demonstrated within the second to sixth months of life in the deaf cat. Potential molecular mechanisms of the existence of sensitive period are discussed. Data from animal research may be compared to electroencephalographic data obtained from cochlear-implanted congenitally deaf children. After cochlear implantation in humans, three phases of plastic adaptation can be observed: a fast one, taking place within the first few weeks after implantation, showing no sensitive period; a slower one, taking place within the first months after implantation (a sensitive period up to 4 years of age); and possibly a third, and the longest one, related to increasing activation of higher order cortical areas.

Origin of hyperactivity in the hamster dorsal cochlear nucleus following intense sound exposure

This study sought to determine whether maintenance of noise-induced dorsal cochlear nucleus (DCN) hyperactivity depends on descending projections. Twenty-two hamsters were exposed under anesthesia to a 10-kHz tone at 125-130 dB SPL for 4 hr, and another 21 unexposed animals served as controls. After approximately 4-6 weeks of recovery, surgical transections were made to isolate the DCN from its adjacent brainstem structures. Spontaneous multiunit activity was recorded from the DCN surface 30-40 min after the surgical manipulations. Spontaneous rates were derived from the recording sites of the DCN along its mediolateral axis for each animal, yielding average spontaneous rates for both control and exposed groups. Histology was performed to assess the degree of sectioning of descending fiber tract connections to the cochlear nucleus, via the acoustic striae route, subpeduncular route, trapezoid body route, and ventral route of the olivocochlear bundle connection. The results showed that complete or nearly complete transections of descending inputs did not affect significantly the magnitude of DCN hyperactivity. However, this manipulation triggered a lateral shift of the peak mean rate, suggesting that descending inputs may play a modulatory role on the profile of DCN hyperactivity. Indeed, exposed animals with transection of only the strial route of entry manifested a level of hyperactivity much higher than that observed in exposed animals in which no sections were performed. This enhancement of DCN hyperactivity was weakened by damage to the subpeduncular or trapezoid routes of input, suggesting that the dorsally located inputs may have an inhibitory effect on DCN hyperactivity.

Tinnitus: neurobiological substrates

Tinnitus is an auditory phantom sensation of ringing in the ears that is experienced when no external sound is present. It is a prevalent disorder that is frequently caused by insults to the peripheral auditory and somatosensory systems, especially in the elderly. This creates an imbalance between inhibitory and excitatory transmitter actions in the midbrain, auditory cortex and brainstem (where neural activity from somatosensory and auditory stimuli interact). This imbalance causes hyperexcitability often leading to the perception of phantom sounds. Although changes in transmitter-receptor systems have become better documented, there are currently no proven drug treatments for humans. Methods for preventing tinnitus have been demonstrated in animal studies.