Hyperbaric oxygen for idiopathic sudden sensorineural hearing loss and tinnitus.

BACKGROUND: This is an update of a Cochrane Review first published in The Cochrane Library in Issue 1, 2005 and previously updated in 2007 and 2009.Idiopathic sudden sensorineural hearing loss (ISSHL) is common and has a significant effect on quality of life. Hyperbaric oxygen therapy (HBOT) may improve oxygen supply to the inner ear and result in an improvement in hearing. OBJECTIVES: To assess the benefits and harms of HBOT for treating ISSHL and/or tinnitus. SEARCH METHODS: We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; Database of Randomised Trials in Hyperbaric Medicine (DORCTHIM); CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the most recent search was 2 May 2012, following previous searches in 2009, 2007 and 2004. SELECTION CRITERIA: Randomised studies comparing the effect on ISSHL and tinnitus of HBOT and alternative therapies. DATA COLLECTION AND ANALYSIS: Three authors evaluated the quality of trials using the 'Risk of bias' tool and extracted data from the included trials. MAIN RESULTS: Seven trials contributed to this review (392 participants). The studies were small and of generally poor quality. Pooled data from two trials did not show any significant improvement in the chance of a 50% increase in hearing threshold on pure-tone average with HBOT (risk ratio (RR) with HBOT 1.53, 95% confidence interval (CI) 0.85 to 2.78, P = 0.16), but did show a significantly increased chance of a 25% increase in pure-tone average (RR 1.39, 95% CI 1.05 to 1.84, P = 0.02). There was a 22% greater chance of improvement with HBOT, and the number needed to treat (NNT) to achieve one extra good outcome was 5 (95% CI 3 to 20). There was also an absolute improvement in average pure-tone audiometric threshold following HBOT (mean difference (MD) 15.6 dB greater with HBOT, 95% CI 1.5 to 29.8, P = 0.03). The significance of any improvement in tinnitus could not be assessed.There were no significant improvements in hearing or tinnitus reported for chronic presentation (six months) of ISSHL and/or tinnitus. AUTHORS' CONCLUSIONS: For people with acute ISSHL, the application of HBOT significantly improved hearing, but the clinical significance remains unclear. We could not assess the effect of HBOT on tinnitus by pooled analysis. In view of the modest number of patients, methodological shortcomings and poor reporting, this result should be interpreted cautiously. An appropriately powered trial is justified to define those patients (if any) who can be expected to derive most benefit from HBOT.There is no evidence of a beneficial effect of HBOT on chronic ISSHL or tinnitus and we do not recommend the use of HBOT for this purpose.

Cochlear nerve stimulation with a 3-dimensional penetrating electrode array.

HYPOTHESIS: An array of penetrating microelectrodes can be implanted into the cochlear nerve to produce stable evoked responses with important electrophysiologic advantages over conventional electrode technology. BACKGROUND: A totally implantable cochlear implant system would benefit from new electrode technology that lowers the current required for stimulation. Modern cochlear implant arrays placed in the scala tympani have an appreciable distance between the electrodes and the cochlear nerve, the site of intended stimulation. This distance can create the problem of cross-talk, limiting the number of electrodes that can represent discrete frequencies over a given length as well as significantly increasing stimulation thresholds and producing nonfocal stimulation of the fibers in the nerve. An electrode in direct contact with neurons in the cochlear nerve could reduce these problems. The Utah Electrode Array is a novel, three-dimensional, penetrating electrode array intended for direct neural stimulation with the potential ability to implant up to 200 electrodes directly into the cochlear nerve. METHODS: Arrays containing 6 to 19 electrodes were implanted acutely into six separate cat cochlear nerves for analysis. Thresholds and input/output functions were measured with electrically induced auditory brainstem responses. RESULTS: Current injections in 38 of 70 implanted electrodes produced stable brainstem responses after implantation. The median threshold was 15 microA. CONCLUSIONS: An array of penetrating electrodes can be implanted into the cochlear nerve and used to evoke brainstem responses. The responses are of low threshold and are stable. Arrays of electrodes, inserted into auditory nerve, could form the neural interfaces for the next generation of auditory prostheses.