Effects of experimental cochlear thrombosis on oxygenation and auditory function of the inner ear

Obstructive Sleep Apnea and Sensorineural Hearing Loss: A Systematic Review and Meta-analysis

OBJECTIVES

To evaluate the associations between obstructive sleep apnea (OSA) and sensorineural hearing loss (SNHL) and the effects of continuous positive airway pressure (CPAP) therapy on SNHL.

DATA SOURCES

Ovid Medline, Embase, and Scopus databases.

REVIEW METHODS

A systematic search was done for studies investigating relationships between OSA and SNHL in adults, with manual searches for additional references. The final update was done on December 22, 2021. The Risk of Bias Assessment Tool for Nonrandomized Studies was applied for quality assessments.

RESULTS

The 20 included studies had a total of 34,442 participants (66% male; mean age, 46.6 years). The OSA group had a significantly worse mean hearing threshold level (HTL) than the control group for midfrequency ranges (500, 1000, 2000 Hz; mean difference, 4.00 dB; 95% CI, 2.40-5.61) and high-frequency ranges (4000, 8000 Hz; mean difference, 6.24 dB; 95% CI, 2.99-9.49). An association between OSA and SNHL was found. When compared with controls, patients with OSA had an odds ratio of 1.52 (95% CI, 1.12-2.06) for midfrequency hearing impairment and 1.19 (95% CI, 1.05-1.34) for high-frequency hearing impairment. However, we did not find significant improvements in midfrequency HTL after CPAP therapy.

CONCLUSIONS

HTL was significantly poorer among participants with OSA (especially in severe cases) than non-OSA controls. Studies on patients with OSA with SNHL treated with CPAP did not show significant improvements in midfrequency HTL. Further studies are warranted on these issues.

Effects of Calcitonin-Gene-Related-Peptide on Auditory Nerve Activity

Calcitonin-gene-related peptide (CGRP) is a lateral olivocochlear (LOC) efferent neurotransmitter. Depression of sound-driven auditory brainstem response amplitude in CGRP-null mice suggests the potential for endogenous CGRP release to upregulate spontaneous and/or sound-driven auditory nerve (AN) activity. We chronically infused CGRP into the guinea pig cochlea and evaluated changes in AN activity as well as outer hair cell (OHC) function. The amplitude of both round window noise (a measure of ensemble spontaneous activity) and the synchronous whole-nerve response to sound (compound action potential, CAP) were enhanced. Lack of change in both onset adaptation and steady state amplitude of sound-evoked distortion product otoacoustic emission (DPOAE) responses indicated CGRP had no effect on OHCs, suggesting the origin of the observed changes was neural. Combined with results from the CGRP-null mice, these results appear to confirm that endogenous CGRP enhances auditory nerve activity when released by the LOC neurons. However, infusion of the CGRP receptor antagonist CGRP (8–37) did not reliably influence spontaneous or sound-driven AN activity, or OHC function, results that contrast with the decreased ABR amplitude measured in CGRP-null mice.

The emergence and prevalence of hearing loss in children with homozygous sickle cell disease

OBJECTIVES

Many children with sickle cell disease (SCD) experience the effect of cochlear insult due to hemolytic anemia and vaso-occlusion that accompanies the disease. As a result, hearing sensitivity eventually decreases. The purpose of this study was to investigate the emergence of hearing loss and the prevalence of such in children with homozygous SCD.

METHODS

A large pediatric database was utilized to gather audiometric outcomes in children with homozygous SCD. Children were identified by primary diagnosis ICD codes. Demographic and audiometric data was drawn to determine presence, type, degree, and laterality of hearing loss. Hearing loss was defined as an elevated audiometric threshold >15 dB HL for pure tone air conduction audiometry or >20 dB HL minimal response level for sound-field testing.

RESULTS

One hundred and twenty-eight children were identified. The prevalence of hearing loss ranged from 28.8% to 50.8% depending on the calculation method (i.e., individual vs. ear specific prevalence and any elevated threshold vs. a three-frequency pure tone average). Conductive hearing loss and bilateral loss were most prevalent. The degree of hearing loss ranged from slight to profound. The mean age of identification of sensorineural hearing loss was 9.6 years.

CONCLUSION

The prevalence of hearing loss in children with homozygous SCD is higher than in normal children. Regular hearing assessments of children with SCD is warranted and should be advocated in early infancy and as part of their ongoing care.

Resistance of Gerbil Auditory Function to Reversible Decrease in Cochlear Blood Flow

The objective was to design in gerbils a model of reversible decrease in cochlear blood flow (CBF) and analyze its influence on cochlear function. In Mongolian gerbils injected with ferromagnetic microbeads, a magnet placed near the porus acusticus allowed CBF to be manipulated. The cochlear microphonic potential (CM) from the basal cochlea was monitored by a round-window electrode. In 13 of the 20 successfully injected gerbils, stable CBF reduction was obtained for 11.5 min on average. The CM was affected only when CBF fell to less than 60% of its baseline, yet remained >40% of its initial level in about 2/3 of such cases. After CBF restoration, CM recovery was fast and usually complete. Reduced CM came with a 35- to 45-dB threshold elevation of neural responses determined by compound action potentials. This method allowing reversible changes of CBF confirms the robustness of cochlear function to decreased CBF. It can be used to study whether a hypovascularized cochlea is abnormally sensitive to stress.

The association between long working hours and hearing impairment in noise unexposed workers: data from the 5th Korea National Health and Nutrition Examination Survey (KNHANES 2010-2012)

BACKGROUND

This study is aimed at finding out the relationship between long working hours, one of major job stress elements, and hearing impairment in unexposed workers to occupational and environmental noise.

METHODS

This study was performed on 1628 regular, full-time wage workers between the age of 25-64 who indicated in the survey of having no experience of exposure to noise, normal otoscopic findings, and not suffering from diabetes based on the data from the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2010-2012). The average working hours per week was categorized into 40 h and lower group, more than 40 to 48 h group, more than 48 to 60 h group, and more than 60 h group. The groups were defined as suffering from low or high frequencies hearing impairment if the average hearing threshold for 0.5, 1, 2 kHz or 3, 4, 6 kHz in both ears exceeds 25 dB based on the pure tone audiometry. The association between average weekly working hours and hearing impairment was analyzed using logistic regression after gender stratification.

RESULTS

The prevalences of low and high frequencies hearing impairment in male workers were 4.3 and 28.6 %, respectively, which were much higher than female's prevalence of 2.7 and 11.1 %. For male workers, no significant association was found between average weekly working hours and low and high frequencies hearing impairment. For female workers, odds ratios (OR) of low and high frequencies hearing impairment were 4.22 (95 % confidence interval (CI) 1.09-16.27) and 4.49 (95 % CI 1.73-11.67), respectively, after controlling for several related factors, such as, age, Body Mass Index (BMI), socio-economic status, health-related behavioral, and occupational characteristics variables, in the final model in the group working more than 60 h compared to the group working 40 h and lower. In addition, a dose-response relationship was observed that ORs of low and high frequencies hearing impairment were increased according to increasing average weekly working hours.

CONCLUSIONS

The association between long working hours and hearing impairment in both low and high frequencies was significant in Korean female workers with a dose-response relationship. Therefore, the law to change the culture of long working hours should be enacted in order to protect the workers' health and improve the quality of life in Korean workers.

Effects of Hyperlipidemia on Noise Induced Hearing Loss (NIHL)

Likelihood of developing noise induced hearing loss (NIHL) is affected by some factors such as genes, nutrition and healthy hearing habits. We investigated this study to determine the effect of hyperlipidemia on NIHL. In a case-control study, 144 workers who exposed to continuous noise more than 85 dBA (88-89 dBA) from a textile factory in Tehran were examined. Serum Blood test results as index for dyslipidemi, were collected and audiometry tests were carried out to analyze the association of hyperlipidemian and NIHL. The mean ±SD of Cholesterol level for NIHL and control were 188.19 (28.46) and 159.00 (26.66) mg/dL respectively. Also the mean ±SD of Triglyceride level for NIHL and control were 203.75 (53.92) and 105.00 (30.50) mg/dL consecutively. After adjusting odds ratio (OR) for NIHL, only hypertriglyceridemia had association with NIHL. (aOR = 1.07; 95 % CI 1.04-1.10), and there wasn't any relation between hypercholestomia and NIHL (aOR = 1.02; 95 % CI 0.99-1.05). Workers with hypertriglyceridemia are at increased risk for NIHL. In factories with elevated noise levels, besides hearing conservation programs, attention to blood serum level of workers and healthy diet are proposed to help in preserving hearing threshold.

Risk of sudden sensorineural hearing loss in patients with psoriasis: a retrospective cohort study

SIGNIFICANCE

Psoriasis, a common immune-mediated disease, affects approximately 2% of the population worldwide. Sudden sensorineural hearing loss (SSNHL) might be a manifestation of systemic vascular involvement in autoimmune disease. However, to the best of our knowledge, there is no systematic English-language examination of the risk of SSNHL in patients with psoriasis.

OBJECTIVES

We tested the hypothesis that psoriasis is a risk factor for developing SSNHL.

METHODS

Using Taiwan's National Health Insurance Research Database, we conducted a retrospective cohort study to compare patients diagnosed with psoriasis from January 1, 2001 through December 31, 2006 (n=28,817) with gender-, age-, and comorbidities-matched controls (n=28,817). We followed each patient until the end of 2011 and evaluated the incidence of SSNHL for at least 6 years after the initial psoriasis diagnosis.

RESULTS

The incidence of SSNHL was 1.51 times higher in the psoriasis cohort than in the control cohort (7.12 vs 4.73 per 10,000 person-years). Using Cox proportional hazard regressions, the adjusted hazard ratio (AHR) was 1.51 (95% confidence interval [CI] 1.18-1.93). Comorbid hypertension was an independent risk factor for SSNHL (AHR 1.49; 95% CI 1.05-2.13). However, the incidence rate ratios (IRRs) for each comorbidity subgroup in the psoriasis and control cohorts were not significantly different.

CONCLUSIONS AND RELEVANCE

Psoriasis was significantly associated with a higher risk of developing SSNHL. We suggest that physicians advise patients with psoriasis to seek medical attention if they have hearing impairments, because they may also have a higher risk of developing SSNHL.

Hyperbaric oxygen therapy with short duration intratympanic steroid therapy for sudden hearing loss

CONCLUSION

The excellent tolerability of intratympanic (IT) steroid offers the possibility to use a high dose, which would appear to be more effective than intravenous (IV) steroid treatment, when both are associated with hyperbaric oxygen (HBO) therapy.

OBJECTIVE

The purpose of the study was to assess for the first time the efficacy of the association of IT steroid and HBO therapy in patients presenting idiopathic sudden sensorineural hearing loss (ISSNHL), comparing this protocol with another consisting of IV steroid administration and HBO therapy.

METHODS

A total of 48 patients presenting ISSNHL were recruited. Patients were divided into two categories: the severe ISSNHL group with a pure-tone average (PTA) between 70 and 90 dB, and the profound ISSNHL group with a PTA >90 dB. The first protocol consisted of 10 days of HBO therapy together with IV methylprednisolone 1 mg/kg body weight for 7 days; the second protocol consisted of HBO therapy for 10 days, associated with an IT injection of prednisolone at a dose of 62.5 mg/ml, once a day for 3 consecutive days, performed 2 h before the HBO therapy.

RESULTS

The overall success rate was superior in the group submitted to IT steroid and HBO therapy. Nevertheless, these clinical results were not statistically significant.

Sudden sensorineural hearing loss: a review of diagnosis, treatment, and prognosis

Sudden sensorineural hearing loss (SSNHL) is commonly encountered in audiologic and otolaryngologic practice. SSNHL is most commonly defined as sensorineural hearing loss of 30 dB or greater over at least three contiguous audiometric frequencies occurring within a 72-hr period. Although the differential for SSNHL is vast, for the majority of patients an etiologic factor is not identified. Treatment for SSNHL of known etiology is directed toward that agent, with poor hearing outcomes characteristic for discoverable etiologies that cause inner ear hair cell loss. Steroid therapy is the current mainstay of treatment of idiopathic SSNHL in the United States. The prognosis for hearing recovery for idiopathic SSNHL is dependent on a number of factors including the severity of hearing loss, age, presence of vertigo, and shape of the audiogram.

Prenatal cocaine exposure accelerates morphological changes and transient expression of tyrosine hydroxylase in the cochlea of developing rats

Prenatal cocaine exposure causes alterations in auditory brainstem response in children and experimental animals and has adverse effects on auditory information processing and language skills in children. These effects may result from lesions in the cochlea since this organ is particularly sensitive to chemical insults during the development. We have thus studied here the effect of prenatal cocaine exposure on the maturation of the rat cochlea using the transient non-catecholaminergic expression of tyrosine hydroxylase in spiral ganglion neurons as an index of cochlear maturation and morphometry to evaluate the maturation of primary auditory neurons and the organ of Corti. We showed that prenatal cocaine exposure accelerated the cochlear maturation. In the basal coil of cochleas from PND8 cocaine-treated pups, the Kölliker's organ had disappeared, the tunnel of Corti was opened, and the stria vascularis no longer contained undifferentiated marginal cells. The maximum expression of tyrosine hydroxylase in type I primary auditory neurons occurred at PND8 instead of PND12 in pair-fed controls. On the other hand, the prenatal cocaine exposure had no effect on the width and height of the organ of Corti, spiral ganglion volume and number and size of primary auditory neurons. In conclusion, our data suggest that prenatal cocaine exposure, though not lethal to primary auditory neurons, accelerates aspects of the cochlear sensorineural maturation. This accelerated cochlear maturation in cocaine-treated rat pups could cause auditory dysfunctions by desynchronizing the development of the whole auditory pathway.

Insights into elevated distortion product otoacoustic emissions in sickle cell disease: Comparisons of hydroxyurea-treated and non-treated young children

Distortion product otoacoustic emissions (DPOAEs) were examined in 15 normal-hearing African-American children between the ages of 6 and 14 years with homozygous sickle cell disease (SCD), who were on a regimen of hydroxyurea (HDU), a drug that reduces inflammatory processes and symptoms of SCD; a matched group of 15 African-American children with homozygous SCD not on HDU; and 15 African-American children with normal hemoglobin. DPOAEs were evoked by 13 primary tone pairs with f2 frequencies ranging from 1000 to 4500 Hz. Increased DPOAE amplitudes, believed to be a precursor of eventual hearing loss, were evident in children with SCD who were not receiving HDU. Those taking HDU had DPOAE amplitudes similar to normal controls. These findings suggest that HDU, in addition to reducing symptoms of SCD, may play a role in inhibiting or preventing cochlear pathology and hearing loss in individuals with SCD.

Cardiovascular and thrombophilic risk factors for idiopathic sudden sensorineural hearing loss

BACKGROUND

In recent years there has been a significant increase in the diagnosis of sudden sensorineural hearing loss (SSHL) in western, countries with an incidence of 20 of 100,000 people affected every year. No clear causes for this disease have been found thus far, but cochlear ischemia has been hypothesized in patients in whom an infectious episode or acoustic neurinoma have been excluded.

OBJECTIVES

The aim of this case-control study was to investigate a number of acquired and inherited thrombophilic risk factors [antithrombin, protein C and S; factor V (FV) Leiden, FII polymorphism; lupus anticoagulant (LA); anticardiolipin (aCL) antibodies; fasting homocysteine (Hcy); lipoprotein(a) (Lp(a)); plasminogen activator inhibitor-1 (PAI-1)] in addition to cardiovascular risk factors in patients with idiopathic SSHL (ISSHL).

PATIENTS AND METHODS

We investigated 155 patients (67 male/88 female; age: 55 (range 19-79 years) with a diagnosis of ISSHL within 30 days from the onset of symptoms, and 155 controls (67 male/88 female; age 54 (range 19-78 years). Fasting Hcy levels were significantly higher in patients than in controls [11.6 (6.7-60) micromol/L vs. 8.7 (5.0-24) micromol/L] as well as PAI-1 levels [19 (2-95) mg/dL vs. 14.5 (4.0-87) mg/dL]. Lupus anticoagulant was present in 13 of 155 (8.4%) patients; 20 patients (12.9%) had positivity of aCL (four IgM and 16 IgG). In no patient was a deficiency of physiological clotting inhibitors antithrombin, protein C and protein S found. No significant differences between patients and controls were observed for Lp(a) plasma levels [111 (1-1146) mg/L vs. 103 (11-695) mg/L] and for the presence of FV Leiden (4.5% vs. 4.5%) and FII variant G20210A (3.8% vs. 3.2%).

RESULTS AND CONCLUSIONS

Independent risk factors for ISSHL at the multivariate analysis (adjusted for age, sex and the traditional cardiovascular risk factors) were the positivity of aCL: OR 5.6 (95% CI 2.0-15.3); cholesterol levels within the second and third tertiles (with respect to the first tertile): T2 = OR 4.8 (95% CI 1.9-12.6)/T3 = OR 19 (95% CI 7-50.1); PAI-1 and Hcy levels within the third tertile (with respect to the first tertile): OR 20 (95% CI 7.8-78) and OR 4.0 (95% CI 2.0-8.1), respectively. These preliminary data suggest that hypercholesterolemia, hyperhomocysteinemia, elevated PAI-1 levels and anticardiolipin antibodies are associated with ISSHL, so indirectly supporting the hypothesis of a vascular occlusion in the pathogenesis of the disease.

Outer hair cell activity of the cochlea in patients with iron deficiency anemia

OBJECTIVE

Iron deficiency anemia is a common disorder, which has been reported to affect the auditory system. However, there are some conflicting points related with the pattern of hearing impairment. The aim of this study is to analyze the outer hair cell activity of the cochlea in patients with iron deficiency anemia.

METHOD

Pure-tone audiometry (PTA) (250-6000 Hz) and distortion product otoacoustic emission (DPOAE) results of 42 patients with iron deficiency anemia and 22 healthy, age and sex matched subjects for the control group were compared. Cubic DPOAEs (2f1-f2) were obtained at 65 and 55 dB sound pressure level (SPL). DP grams were plotted as a function of f2 and signal-to-noise ratio (SNR) was specified as the difference in decibels SPL between DPOAE amplitude and the ambient noise level at a given f2. In DP grams, DP amplitudes and noise levels obtained from the baseline measurements were presented as the upper and lower limits of DP amplitude and noise level that were the 10th and 90th percentiles calculated by adding and subtracting standard deviations and from mean baseline DP amplitude and noise level. Independent-samples t-test is used for comparison of the groups.

RESULTS

Pure-tone audiometry was normal in patients with iron deficiency anemia and control subjects and there was no significant difference in comparison of DPOAE in both groups and both sides and the results were between two percentiles (P > 0.05).

CONCLUSION

The results of the present study did not support a casual relationship between the iron deficiency anemia and the auditory dysfunction on the basis of DPOAE.

Platelet GPIaC807T polymorphism is associated with negative outcome of sudden hearing loss

To determine the relevance of inherited prothrombotic risk factors in sudden hearing loss, we investigated 85 patients with sudden hearing loss of >/= 60 dB for the presence of inherited prothrombotic risk factors. The FV G1691A, FII G20210A, GPIa C807T, GPIIIa PIA1/A2, PAI-1 4G/5G, t-PA Alu repeat ID, MTHFR C677T and CBS 844ins68 genotypes were investigated. Allele frequencies found in patients were compared to those of 85 healthy control subjects of the same ethnic background using Chi-squared and odds-ratio analysis. The frequency of the GPIa807T allele was significantly elevated in patients compared to controls. In addition, allele frequency and genotype distribution of GPIa was significantly elevated in the patient group without recovery after 3 months of sudden hearing loss onset. Allele frequencies of all other prothrombotic risk factors investigated here did not differ from those of the control subjects. The single-nucleotide polymorphism of GPIa C807T seems to play a role as a prognostic factor in recovery from sudden hearing loss.

Susceptibility of the hair cells of the newborn rat cochlea to hypoxia and ischemia

Hypoxia and ischemia are thought to be important pathogenetic factors in bringing about hearing loss. In order to study the effect of these determinants on the loss of inner and outer hair cells (IHCs/OHCs), we used an in vitro hypoxia and ischemia model of the newborn rat cochlea. The specimens of the organ of Corti were exposed either to hypoxia (10-20 mm Hg) or to normoxic glucose deprivation or to both (ischemia) in artificial perilymph for different exposure periods. The number of IHCs and OHCs was counted and the hair cell loss was compared to controls. Normoxic aglycemia did not cause significant hair cell loss as compared to controls. Hypoxia and ischemia led to hair cell loss in a dose-dependent manner, with the loss in the ischemia groups found to be markedly higher than that in the hypoxia groups. Hypoxia resulted in a mean loss of 8% OHC and of 14% IHC after an 8-h exposure. Ischemia increased the loss to 19% OHC and 39% IHC after the same exposure period of 8 h. Our findings suggest that IHCs are more susceptible to hypoxia/ischemia than OHCs.

Distortion product otoacoustic emissions in normal-hearing children with homozygous sickle cell disease

The purpose of this study was to investigate distortion product otoacoustic emissions (DPOAEs) in young normal-hearing children with sickle cell disease (SCD). It was hypothesized that the prevalence of DPOAEs and response amplitudes would be lower than those in children with normal hemoglobin due to suspected compromised cochlear function as a result of vaso-occlusive events characteristic of SCD. Twenty African-American children with SCD and 15 African-American children with normal hemoglobin participated. Distortion product OAEs were evoked by 13 primary tone pairs with f2 frequencies ranging from 1000 to 4500 Hz. The primary tones were presented at L1 and L2 levels of 70 and 60 dB SPL (high) and 50 and 40 dB SPL (low), respectively. The findings of this study were completely unexpected and contrary to our original hypotheses. The likelihood of detecting a DPOAE response was not related to the clinical status of the children. Distortion product OAE amplitudes were significantly larger for children with SCD (p =.01).

Laser Doppler measurements of inner ear blood flow during experimental thrombosis of cochlear blood vessels in the guinea pig

This study investigated the vascular effect of ferromagnetic obstruction of cochlear blood vessels in the guinea pig using dual-channel laser Doppler flowmetry. To improve this technique, we tested new types of magnets and iron spheres. In so doing, the cochlear temperature was lowered selectively and general hypothermia was avoided. The success of vascular impairment in the inner ear was found to depend on the experimental conditions used. Given normothermic conditions (38 degrees C body temperature), a clear reduction in cochlear blood flow (CBF) was found in only about 30% of the animals tested when an aluminium-nickel-cobalt alloy magnet and carbonyl iron spheres were used, while this ratio increased to about 80% under general hypothermia (33 degrees C). Using a stronger neodymium-iron-boron magnet and smaller-sized iron spheres, we found the success of vascular obstruction to be approximately 70% under normothermia and 100% with local hypothermia (to 33 degrees C) of the cochlea. Although the extent of vascular impairment revealed a considerable interindividual variation, the present findings demonstrate that ferromagnetic intervention in CBF with dual-channel laser Doppler flowmetry can be used to investigate the effect of quantified cochlear ischemia on inner ear physiology in the guinea pig model and test various therapeutic strategies.