Effectiveness of hyperbaric oxygen therapy in patients with acute and chronic cochlear disorders

Standard cochlear implants as electrochemical sensors: Intracochlear oxygen measurements in vivo

Cochlear implants are the most successful neural prostheses worldwide and routinely restore sensorineural hearing loss by direct electrical stimulation of the auditory nerve. Enhancing this standard implant by chemical sensor functionality opens up new possibilities, ranging from access to the biochemical microenvironment of the implanted electrode array to the long-term study of the electrode status. We developed an electrochemical method to turn the platinum stimulation microelectrodes of cochlear implants into electrochemical sensors. The electrodes showed excellent and stable chemical sensor properties, as demonstrated by in vitro characterizations with combined amperometric and active potentiometric dissolved oxygen and hydrogen peroxide measurements. Linear, stable and highly reproducible sensor responses within the relevant concentration ranges with negligible offset were shown. This approach was successfully applied in vivo in an animal model. Intracochlear oxygen dynamics in rats upon breathing pure oxygen were reproducibly and precisely measured in real-time from the perilymph. At the same time, correct implant placement and its functionality was verified by measurements of electrically evoked auditory brainstem responses with clearly distinguishable peaks. Acute measurements indicated no adverse influence of electrical stimulation on electrochemical measurements and vice versa. Our work is ground-breaking towards advanced implant functionality, future implant lifetime monitoring, and implant-life-long in situ investigation of electrode degradation in cochlear implant patients.

Hyperbaric oxygen therapy as salvage treatment for sudden sensorineural hearing loss: review of rationale and preliminary report

Background:

The management of sudden sensorineural hearing loss has not yet been standardised. Hyperbaric oxygen therapy influences recovery from sudden sensorineural hearing loss, but the underlying mechanism is unknown and the appropriate indications and protocols undetermined.

Materials and methods:

Nineteen patients affected by sudden sensorineural hearing loss were treated after unsuccessful medical therapy, either in an acute or chronic setting. Pure oxygen inhalation at 2.5 atmospheres absolute pressure was administered for 90 minutes, for 30 sessions. Frequency-specific and average pure tone hearing thresholds were determined before and after hyperbaric oxygen therapy. The number of hyperbaric oxygen therapy sessions, the patient's age and any therapeutic delay were considered as quantitative variables possibly influencing outcome. Stepwise multivariate analysis was performed.

Results:

Salvage hyperbaric oxygen therapy appeared to improve patients' pure tone hearing thresholds, particularly at low frequencies. Positive results were more likely with increased patient age and reduced delay in receiving hyperbaric oxygen therapy.

Conclusion:

Hyperbaric oxygen therapy has a strong scientific rationale, and improves pure tone hearing thresholds in cases of sudden sensorineural hearing loss unresponsive to medical therapy. Further research may be able to identify those patients with sudden sensorineural hearing loss for whom hyperbaric oxygen therapy would be most cost-effective.

Hyperbaric oxygen in the treatment of sudden deafness

Currently, the treatment of sudden deafness (SD) is based mainly on complete bed rest and the administration of corticosteroids. Hyperbaric oxygen therapy (HBOT) has previously been suggested as adjunctive treatment. We describe two cases of successful HBOT for SD. The first patient presented with moderate mid-frequency hearing loss without accompanying symptoms, whereas the second patient had moderate low-frequency hearing loss with persistent tinnitus and a single episode of vertigo. HBOT in addition to conventional treatment soon after diagnosis resulted in full recovery of hearing in both patients. The pathogenesis of SD may involve a reduction in cochlear blood flow and perilymph oxygenation, making early HBOT a reasonable treatment modality for this condition.

Hyperbaric oxygen and steroid therapy for idiopathic sudden sensorineural hearing loss

In our controlled retrospective analysis of medical records in tertiary care academic medical center, we aimed to investigate the therapeutic effects of hyperbaric oxygen (HBO) therapy combined with steroid administration for idiopathic sudden sensorineural hearing loss (ISSNHL) in comparison with that of steroid administration alone. Our subjects were 130 consecutive inpatients with ISSNHL (hearing levels >/=40 dB; time from the onset of hearing loss to the start of treatment </=30 days). Sixty-seven patients underwent HBO plus steroid therapy (HBO group), and 63 were given steroids alone (steroid group). Hearing recovery was evaluated by grade assessment and by the improvement in hearing compared to that in the unaffected contralateral ear. The cure rate and hearing improvement rate were not statistically different between the two groups; however, the recovery rate was significantly higher in the HBO group than in the steroid group (59.7% vs. 39.7%; P < 0.05). With regard to patients with initial hearing levels of >/=80 dB, the hearing improvement rate was significantly higher in the HBO group than in the steroid group (51.1 +/- 7.0% vs. 27.1 +/- 7.8%; P < 0.05), while in patients whose initial hearing levels were <80 dB, hearing outcomes were not statistically different between the two groups. In both the HBO and steroid groups, patients with initial hearing levels of <80 dB showed a better hearing improvement rate than those with initial hearing levels of >/=80 dB. In conclusion HBO therapy shows a significant additional effect in combination with steroid therapy for ISSNHL, particularly in patients with severe hearing loss.

General review of tinnitus: prevalence, mechanisms, effects, and management

Tinnitus is an increasing health concern across all strata of the general population. Although an abundant amount of literature has addressed the many facets of tinnitus, wide-ranging differences in professional beliefs and attitudes persist concerning its clinical management. These differences are detrimental to tinnitus patients because the management they receive is based primarily on individual opinion (which can be biased) rather than on medical consensus. It is thus vitally important for the tinnitus professional community to work together to achieve consensus. To that end, this article provides a broad-based review of what is presently known about tinnitus, including prevalence, associated factors, theories of pathophysiology, psychological effects, effects on disability and handicap, workers' compensation issues, clinical assessment, and various forms of treatment. This summary of fundamental information has relevance to both clinical and research arenas.

Habituation deficit in auditory event-related potentials in tinnitus complainers

According to Hallam's habituation theory of tinnitus, most of the suffering caused by tinnitus is due to difficulties in habituation to the perceived tinnitus sound. Thus tinnitus complainers are assumed to display a less pronounced habituation as compared to tinnitus non-complainers. In the present study, an experimental test of this theory was undertaken using event-related potentials (ERPs) as indicators of habituation to exogenously administered tone pips. In 22 patients (10 tinnitus complainers and 12 tinnitus non-complainers) and 10 healthy controls, the habituation of ERPs to series of auditory stimuli across four consecutive trials was studied. Diminuition of the N(1) and P(2) amplitudes of the ERPs was taken to measure the habituation process across the trials. Tinnitus complainers showed a less distinct habituation of the N(1)-P(2) amplitude difference (vertex potential) compared to tinnitus non-complainers. The results are in accordance with Hallam's theory and support the notion that patients with a severe tinnitus fail to properly habituate to auditory stimuli.

Alternative medications and other treatments for tinnitus: facts from fiction

Tinnitus is a significant medical problem affecting approximately 50 million Americans, 12 million of them severely. Once a thorough evaluation has been performed by a qualified otolaryngologist, and no life-threatening pathology has been identified, the opportunity for treatment exists. Treatment options are extensive and range from approved protocols to anecdotal remedies. Although tinnitus may not miraculously disappear, many therapeutic options exist that may help to make the tinnitus more manageable.

Recent advances in the pharmacological treatment of tinnitus

Tinnitus is an extremely prevalent condition that impinges on the lives of sufferers to varying degrees. In some people, it is a fairly minor irritation but, for many, the tinnitus intrudes to such a degree that it affects their ability to lead a normal life, and in some very extreme cases has resulted in suicide. Insomnia, inability to concentrate and depression are commonly reported to accompany the condition. Relief can be reliably obtained using intravenous lignocaine, which indicates that pharmacology can provide a route for effective alleviation of the condition. In this article, Julie Simpson and Ewart Davies review the potential pharmacological therapies, and emphasize that clinical research has been hampered by the absence of a reliable objective assessment of the tinnitus and by the variable nature of the complaint.