Analysis of Vestibular Evoked Myogenic Potentials and Electrocochleography in Noise Induced Hearing Loss.

OBJECTIVE: Our objective was to analyze the electrocochleography (ECoG) and cervical vestibular evoked myogenic potential (cVEMP) results of patients with noise-induced hearing loss (NIHL). MATERIALS AND METHODS: The study included 20 patients with NIHL. Pure-tone audiometry, tympanic membrane ECoG, and cVEMP were performed on all patients. The patients were divided into two groups based on averaged thresholds at 4, 6, and 8 kHz; whereby, group 1 comprised patients who had a threshold higher than 68.3 dB HL, whereas group 2 comprised patients with a threshold lower than 68.3 dB HL. RESULTS: Group 2 had a significantly higher number of patients with abnormal cVEMP values (63% versus 28%) (p=0.028). There was no significant difference in the incidence of ECoG abnormality between the groups (p>0.05), but there was a significant difference in the incidence of recognizable ECoG potentials between the groups (p<0.05). When only patients with vertigo/dizziness were considered, the group with vertigo and a lower degree of hearing loss (group 2) showed a higher incidence of abnormal cVEMP (p<0.05). CONCLUSION: Although the anatomical proximity of the sacculus to the cochlea leads to the consideration of a common involvement of these structures in NIHL, our results did not support the idea of a common and proportional involvement of the vestibular and auditory systems. Our study shows that saccular involvement is disproportionate to auditory involvement in NIHL.

Effects of hyperbaric oxygen and dexamethasone on proinflammatory cytokines of rat cochlea in noise-induced hearing loss.

HYPOTHESIS: To investigate effects of dexamethasone and hyperbaric oxygen therapy (HBOT) on proinflammatory cytokines and hearing levels in the noise-exposed cochlea of rats. BACKGROUND: There is an arising concern about negative effects of early initiation of HBOT on hearing in noise-induced hearing loss. Furthermore, effects of HBOT and dexamethasone on cochlear cytokines are not fully elucidated. METHODS: Twenty-six rats were divided into 3 groups: control, noise, and treatment groups. Five rats served as control group. White noise at 115 dB sound pressure level was applied to the noise group of 4 rats for 10 days. This group was assigned to a positive control group as it was equivalent to treatment groups. The treatment group of 17 rats underwent the same noise exposure, and then, they were divided into 3 groups based on treatment protocol: 5 and 6 rats received HBOT at the third hour and 24th hour after the noise, respectively, and 6 rats received dexamethasone. Auditory brain stem response threshold was measured in all groups before being assigned to the groups, after the noise exposure and right before being killed. Cytokine levels at the cochlear soft tissues were measured using enzyme-linked immunoassay. RESULTS: Final thresholds (10 dB and 5 dB nHL-normal hearing level) of HBOT-24th hour and dexamethasone groups were significantly better than that of untreated noise group (22.5 dB nHL) (p < 0.05). There was no significant difference between HBOT-24th hour group (10 dB nHL) and dexamethasone group (5 dB nHL) (p > 0.05). IL-6 and IL-1ß of HBOT-third hour group (2.30 ng/mg and 185.43 pg/mg) were significantly higher than those of the noise group (0.91 ng/mg and 131.40 pg/mg), dexamethasone group (1.19 ng/mg and 112.29 pg/mg) and HBOT-24th hour group (1.34 ng/mg and 106.69 pg/mg) (p < 0.05). There was no significant difference in IL-6 and IL-1ß of HBOT-24th hour group, dexamethasone group, noise group, and control group (p > 0.05). There was no significant difference in TNF-α of the 3 treatment groups, noise group, and control group (p > 0.05). CONCLUSION: The results showed that the most effective method in the treatment of noise-induced hearing loss was early initiation of dexamethasone therapy. There could be negative effects of HBOT on hearing if it is commenced early after the noise (first 3 h). HBOT treatment, which was started at the 24th hour, was found to be an effective method.

Middle ear barotrauma with hyperbaric oxygen therapy: incidence and the predictive value of the nine-step inflation/deflation test and otoscopy.

We conducted a prospective study to determine the incidence of middle ear barotrauma in patients who were undergoing hyperbaric oxygen therapy (HBOT). We also investigated the value of the nine-step inflation/deflation test and otoscopic findings before and immediately after the initial HBOT session in predicting barotrauma in an attempt to establish some criteria for prophylaxis. The study was conducted on 36 ears of 18 adults who had no history of eustachian tube dysfunction. Patients were being treated with HBOT for sudden hearing loss, wound-healing complications, or complications of diabetes. After 7 days of HBOT, barotrauma was seen in 12 of the 18 patients (66.7%) and in 18 of the 36 ears (50.0%). The nine-step inflation/deflation tests, which were performed before and immediately after the initial HBOT session, were not predictive of barotrauma (p = 0.095 before and p = 0.099 after). However, otoscopic findings obtained immediately after the first session of HBOT were predictive of barotrauma, with a sensitivity and specificity of 83 and 100%, respectively. We conclude that patients with even minor positive pathologic findings on otoscopy immediately following HBOT are at increased risk of middle ear barotrauma if HBOT is to be continued without prophylaxis.

Transcutaneous electrical stimulation of subjective tinnitus. A placebo-controlled, randomized and comparative analysis.

AIM: The effect of the transcutaneous application of the electrical stimulus on tinnitus perception has been reviewed in a placebo-controlled, randomized and comparative analysis to eventually determine the outcome of the therapeutic role of the therapy. METHOD: There are 42 patients who were randomized into 2 groups according to their order of admission. Group A consists of 31 patients who were subjected to transcutaneous electrical stimulation 3 times a week for 1 month. Group B includes 11 patients who had electrical stimulus attachment but where no stimulus was given (placebo group). The stimulator is a custom-made device which generates direct and alternative current in 10-200 Hz frequency. An alternative low-frequency (not >100 Hz) pulsed current was used for tinnitus therapy through a preauricular skin electrode. The amplitude of stimulus ranged between 50 and 2,000 mA. The pulse frequency was 30 Hz. Each session lasted for 25 min for both groups. Statistical analysis was performed. RESULT: The rate of improvement following the therapy was 42.8% (18/42) in the electrical therapy group and 28.5% (4/14) in the placebo group. CONCLUSION: Electrical suppression of the tinnitus does not offer a promising outcome for patients with tinnitus in the presented study.

Identification and characterization of choline transporter-like protein 2, an inner ear glycoprotein of 68 and 72 kDa that is the target of antibody-induced hearing loss.

The Kresge Hearing Research Institute-3 (KHRI-3) antibody binds to a guinea pig inner ear supporting cell antigen (IESCA) and causes hearing loss. To gain insight into the mechanism of antibody-induced hearing loss, we used antibody immunoaffinity purification to isolate the IESCA, which was then sequenced by mass spectroscopy, revealing 10 guinea pig peptides identical to sequences in human choline transporter-like protein 2 (CTL2). Full-length CTL2 cDNA sequenced from guinea pig inner ear has 85.9% identity with the human cDNA. Consistent with its expression on the surface of supporting cells in the inner ear, CTL2 contains 10 predicted membrane-spanning regions with multiple N-glycosylation sites. The 68 and 72 kDa molecular forms of inner ear CTL2 are distinguished by sialic acid modification of the carbohydrate. The KHRI-3 antibody binds to an N-linked carbohydrate on CTL2 and presumably damages the organ of Corti by blocking the transporter function of this molecule. CTL2 mRNA and protein are abundantly expressed in human inner ear. Sera from patients with autoimmune hearing loss bind to guinea pig inner ear with the same pattern as CTL2 antibodies. Thus, CTL2 is a possible target of autoimmune hearing loss in humans.

The role of zinc in management of tinnitus.

OBJECTIVE: Several therapeutic modalities have been tried in patients with tinnitus. These trials have given rise to unsatisfactory results in most of the patients since the etiology and pathophysiology of tinnitus is unclear. Significant correlation between tinnitus and decreased zinc level and also reduction in severity of tinnitus after zinc therapy has been reported in some clinical studies. The aim of this study is to find out the prevalence of hypozincemia in patients suffering from tinnitus of various origins (presbyacusis, acoustic trauma and ototoxicity) at young and elderly population and to investigate the effect of zinc therapy upon the severity of tinnitus. METHODS: Forty consecutive patients with severe tinnitus were included in this study between April 1998 and May 2000. There were 32 men (80%) and eight women (20%) with an age ranging between 19 and 67 (mean 40.6 years). Eleven patients were over the age of 50. The zinc level was measured in non-diluted serum by flame atomic absorption spectrophotometry (normal values; 50-120 microg/dl) from fasting blood samples. All the patients were given zinc pills 220 mg each, once a day and 2 h before lunch for 2 months. The patients were required to fulfill a tinnitus scoring scale and a handicap questionnaire before and after treatment. The Wilcoxon rank sum test and McNemar test were used for the statistical analysis. RESULTS: Six patients were hypozincemic and seven patients had decreased serum zinc levels. No significant change has been observed in frequency and severity of tinnitus measured by audiologic tests after zinc therapy. Twenty-three (57.5%) of these patients reported some relief of tinnitus in the tinnitus scoring scale but the rate of improvement was minor (P>0.05). Decrease in severity of tinnitus after zinc therapy in elder group was better than the younger ones. CONCLUSION: Our study could not confirm the high incidence of hypozincemia in patients with tinnitus as reported previously. Zinc therapy for 8 weeks presented no promising effect on tinnitus in three groups of patients and the difference between the rate of improvement in severity of tinnitus after zinc intake in patients with normal and low serum zinc level was not significant. Zinc supplement provided relief of tinnitus in some of the elder people who apparently had dietary zinc deficiency.