Glucocorticoids and dehydroepiandrosterone sulfate ameliorate ischemia-induced injury of the cochlea

Salvage therapy for refractory sudden sensorineural hearing loss (RSSNHL): a systematic review and network meta-analysis

OBJECTIVE

Approximately 30-50% of sudden sensorineural hearing loss (SSNHL) patients show poor response to systemic steroid therapy. Additionally, the most appropriate treatment for patients with refractory sudden sensorineural hearing loss (RSSNHL) is unknown. This study aimed to explore the best treatment for RSSNHL.

DESIGN

Using a frequentist contrast-based model and PRISMA guidelines, this study compared five salvage regimes: intratympanic injection of steroids (ITS), hyperbaric oxygen (HBO) therapy, post auricle steroid injection (PSI), ITS combined with HBO therapy, and continued systemic steroids.

STUDY SAMPLE

We searched the PubMed, EMBASE, Web of Science, and Cochrane Library databases for randomised controlled trials and cohort studies comparing treatment regimens for RSSNHL.

RESULTS

Compared with the control group (no additional treatment), PSI and ITS demonstrated significant improvements. The mean hearing gain was greater after PSI (11.1 dB [95% CI, 4.4-17.9]) than after ITS (7.7 dB [95% CI, 4.8-10.7]). When a restricted definition of RSSNHL was used, the ITS + HBO therapy showed the largest difference in improvement for pure tone average compared with the control group (14.5 dB [95% CI, 4.2-25.0]).

CONCLUSIONS

The administration of either PSI or ITS leads to the greatest therapeutic effect in patients with RSSNHL. However, a consensus on the definition of RSSNHL is needed.

Long-term exposure to high-concentration dexamethasone in the inner ear via intratympanic administration

The first-line treatment for inner ear disorders is usually oral/systemic steroids. Intratympanic steroid therapy is an alternative option; however, it requires multiple office visits owing to the short residence time of steroids in the inner ear (systemic: 24 h, intratympanic: 2-3 h). Therefore, intratympanic injections of higher steroid concentrations could result in longer drug exposure, providing better treatment outcomes. This study aimed to develop a prototype for high-concentration steroids and examine their safety and feasibility in vivo. Using wild-type Institute for Cancer Research mice, high-concentration steroids (50 mg/mL dexamethasone), typical steroid concentrations (3.3 mg/mL dexamethasone), and sterile saline were administrated into the middle ear cavity via tympanic membrane injection. Auditory brainstem response analysis, vestibular function tests, and morphological analyses were performed to examine the safety and utility of High-conc Dex. One month post-injection, the frequency-averaged auditory brainstem response thresholds of high-dose dexamethasone-treated mice were not significantly different from those of low-dose dexamethasone- and saline-treated mice at all tested frequencies. Furthermore, the total points on vestibular function tests were similar between the three groups. Morphologically, no damage to the inner ear/middle ear mucosa was observed in all groups. Two months post-injection, dexamethasone could still be detected in the high-dose dexamethasone group. Altogether, our data successfully demonstrates the feasibility and safety of high-dose dexamethasone for in vivo use in the middle ear and ensure that the drug localizes to the inner ear. Further research is warranted to develop this new treatment strategy and further characterize its effects in vivo.

Combined Intratympanic and Systemic Steroid Therapy in Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSNHL) is a true otological emergency that must be diagnosed and treated immediately. This study aimed to assess the efficacy of treatment with intratympanic dexamethasone (ITD) plus oral prednisolone with that of oral prednisolone or intratympanic dexamethasone alone and to determine factor affecting treatment outcome for SSNHL. Forty-five patients with SSNHL that had been present within 2 weeks of onset of symptoms were included in this prospective case control study. Patients were allocated to three different groups. Patients in group A were treated with oral prednisolone 1 mg/kg/d full dose 14 days then tapered over next 14 days. Patients in group B were treated with ITD 0.5 ml (4 mg/ml) every 7 days for a total 4 weeks along with oral prednisolone 1 mg/kg/d in tapering dose for 4 weeks. Patients in group C were got ITD 0.5 ml (4 mg/ml) every 7 days for a total 4 weeks. Audiogram was performed before each subsequent injection and at completion of treatment course. Among all participants, 22 patients (48.89%) showed improvement in pure tone audiogram to within 50% of pre- sudden hearing loss. On comparing the results of group A, B and C, there were no statistically significant difference with each other (p value 0.185). The mean audiometric gain was 37.71 dB in recovered cases. The combination therapy of intratympanic dexamethasone and oral steroid is more effective in comparison with intratympanic or oral steroid alone in the treatment of SSNHL as the patients benefitted from the therapeutic effects of both local and systemic steroids.

Hearing loss is associated with hippocampal atrophy and high cortisol/dehydroepiandrosterone sulphate ratio in older adults

OBJECTIVES

Hearing loss (HL) has been recognised as a prodromal symptom of cognitive disorder with aging. It is still uncertain if HL leads to cognitive impairment directly or through an indirect mechanism.

DESIGN

Participants of this study underwent an auditory test, blood tests, and brain MRI. The atrophy rate of the hippocampus (HP) was calculated using voxel-based specific areas. A partial correlation analysis whilst controlling for the effect of age was performed to analyse the factors affecting hearing levels and HP atrophy rate (HP%).

STUDY SAMPLE

Thirty-six older adults with hearing impairment.

RESULTS

The group of participants with moderate or severe HL (n = 22) had higher cortisol/dehydroepiandrosterone sulphate (C/D) ratio, geriatric depression score (GDS) and HP% than the mild HL or normal hearing group (n = 14, p < 0.05). The HP% showed a significant positive correlation with the C/D ratio, GDS and the hearing level of high frequency (HF) (p < 0.05). The C/D ratio was positively correlated with the HP% and the hearing level of the HF (p < 0.05).

CONCLUSIONS

Our results suggest that the HL is associated with the atrophy of HP and high C/D ratios in older adults; however, HL may not be causally related to hippocampal atrophy.

Early Intratympanic Methylprednisolone in Sudden SNHL: A Frequency-wise Analysis

Sudden sensorineural hearing loss is a dire medical emergency which must be treated at the earliest to get better long term hearing results. Our study aims to determine the efficacy of intratympanic steroid (Methylprednisolone) on auditory outcomes in patients of sudden sensorineural hearing loss and study the relation between time of onset of hearing loss to start of therapy and frequency-wise recovery of hearing loss. A prospective cohort clinical study with 33 patients with sudden hearing loss of 30 dB or more were treated with the intratympanic injection of methylprednisolone and the effect of the drug was observed. In this study, 33 patients with sudden onset (unilateral or bilateral) of hearing loss were treated with intratympanic methylprednisolone. The duration at which the drug was administered and the age of the participants was taken into consideration. Main outcome measures included audiometry results at low, medium and high hearing loss frequencies. The specific frequency at which the hearing improvement took place was tabulated. It was observed that hearing improved significantly if the steroid is injected within the first 4 days of onset (p < 0.05) at all the frequencies. A gain of 15 dB or more was achieved in more than 78% patients after injecting methylprednisolone intratympanically. A statistically significant association was found between recovery rate and frequency of hearing loss with patients showing greater improvement at low hearing loss frequency in comparison to mid and high frequencies (p < 0.05). The drug efficacy does not change with the age of the patient.

An exploratory pilot investigation of neurosteroids and self-reported pain in female Iraq/Afghanistan-era Veterans

Female Veterans are the most rapidly growing segment of new users of the Veterans Health Administration (VHA), and a significant proportion of female Veterans receiving treatment from VHA primary care providers report persistent pain symptoms. Currently, available data characterizing the neurobiological underpinnings of pain disorders are limited. Preclinical data suggest that neurosteroids may be involved in the modulation of pain symptoms, potentially via actions at gamma-aminobutyric acid (GABA) and N-methyl-D-aspartate (NMDA) receptors. Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) are neurosteroids that modulate inhibitory GABA receptors and excitatory NMDA receptors, producing complex neuronal effects. Emerging evidence from male Iraq/Afghanistan-era Veterans suggests that reductions in neurosteroid levels are associated with increased pain symptoms and that neurosteroids may be promising biomarker candidates. The current exploratory study thus examined associations between self-reported pain symptoms in 403 female Iraq/Afghanistan-era Veterans and serum DHEAS and DHEA levels. Serum DHEAS levels were inversely correlated with low back pain in female Veterans (Spearman r = -0.103; p = 0.04). Nonparametric analyses indicate that female Veterans reporting moderate/extreme low back pain demonstrated significantly lower DHEAS levels than those reporting no/little low back pain (|Z| = 2.60; p = 0.009). These preliminary findings support a role for DHEAS in pain physiology of low back pain and the rationale for neurosteroid therapeutics in pain analgesia.

Intratympanic glucocorticosteroid therapy for idiopathic sudden hearing loss: Meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

Glucocorticoids are the standard treatment for idiopathic sudden sensorineural hearing loss (ISSNHL), but whether intratympanic or systemic therapy is superior remains controversial. Previous meta-analyses of this question have omitted key clinical trials or included observational studies.

METHODS

English-language randomized controlled trials in OvidSP, PubMed, Embase, CINAHL, and the Cochrane Library comparing intratympanic versus systemic glucocorticoid therapy for ISSNHL were meta-analyzed using RevMan 5.3. The primary outcome of interest was improvement in pure tone average (PTA) threshold.

RESULTS

Six trials involving 248 patients receiving intratympanic steroids and 236 receiving systemic steroids were meta-analyzed. PTA thresholds were similar between the 2 groups at 3 months after therapy initiation (mean difference, 0.24; 95% confidence interval [CI] -2.43 to 2.91, P = .86; I = 54%, P = .07, random-effects model). PTA thresholds were also similar at 6 months (mean difference, 4.69, 95% CI -5.84 to 15.22, P = .38), although the results showed extremely high heterogeneity (I = 98%). Sensitivity analysis indicated that a single trial containing 250 patients provided the strongest evidence for equivalence between the 2 types of therapy. Rates of recovery within 3 months (defined as PTA improvement >10 dB) were similar between the 2 types of therapy (odds ratio 0.92, 95% CI 0.59-1.43, P = .70), with no significant heterogeneity in the pooled data (I = 1%, P = .40).

CONCLUSION

Intratympanic and systemic steroids' therapies appear to show similar short-term efficacy for restoring hearing in patients with ISSNHL. Intratympanic therapy may reduce systemic side effects associated with steroid use.

The Protective Effect of Intratympanic Dexamethasone on Streptomycin Ototoxicity in Rats

The purpose of this experimental study was to investigate the protective role of intratympanically administered dexamethasone on the inner ears of rats that were exposed to streptomycin ototoxicity. Twenty-four adult Wistar albino rats were separated into 4 groups: Group 1 (only streptomycin), Group 2 (only intratympanic dexamethasone), Group 3 (streptomycin and intratympanic dexamethasone), and Group 4 (streptomycin and intratympanic saline). All rats were evaluated with distortion product otoacoustic emissions (DPOAE) tests before the start of treatment and on the day it ended. On the 45th day, after the final DPOAE tests, animals of all groups were sacrificed under general anesthesia. The differences between the amplitudes of DPOAE results were determined, and hearing results were statistically analyzed. Also, the cochleas of each rat were histopathologically evaluated under a light microscope with hematoxylin and eosin staining. In the intratympanic dexamethasone group it was observed that cochlear hair cells were mostly protected. No significant difference was seen between the DPOAE results before and after treatment (p > 0.05). On the other hand, loss was observed in the hearing functions and hair cells of the rats that received streptomycin and streptomycin plus intratympanic saline (p < 0.05). In the streptomycin plus intratympanic dexamethasone group, the cochlear hair cells were partially protected. A significant difference was observed when the DPOAE results (DP-grams) of the streptomycin plus intratypmanic dexamethasone group were compared to those of the streptomycin plus intratympanic saline group (p < 0.05). After the experimental study, ototoxic effects of the administration of streptomycin and intratympanic dexamethasone were observed on the rats’ cochlear hair cells. We conclude that intratympanic dexamethasone has protective effects against this cochlear damage in rats.

Risk of sudden sensorineural hearing loss in stroke patients: A 5-year nationwide investigation of 44,460 patients

Poststroke sudden sensorineural hearing loss (SSNHL) can hinder communication between patients and healthcare professionals, thereby restricting participation in rehabilitation programs and limiting improvements in physical performance. However, the relationship between stroke and SSNHL remains unclear. This study employed a nationwide population-based dataset to investigate the relationship between stroke and SSNHL.The Taiwan Longitudinal Health Insurance Database was used to compile data from 11,115 stroke patients and a comparison cohort of 33,345 matched nonstroke enrollees. Each patient was followed for 5 years to identify new-onset SSNHL. Stratified Cox proportional-hazard regression analysis was used to examine the association of stroke with subsequent SSNHL.Among the 44,460 patients, 66 patients (55,378 person-years) from the stroke cohort and 105 patients (166,586 person-years) from the comparison cohort were diagnosed with SSNHL. The incidence of SSNHL was approximately twice as high among stroke patients than among nonstroke patients (1.19 and 0.63/1000 person-years, respectively). Stroke patients had a 71% increased risk of SSNHL, compared with nonstroke patients (adjusted hazard ratio [HR] 1.71, 95% confidence interval [CI] 1.24-2.36). We also observed a remarkable increase in risk of SSNHL in stroke patients within 1-year of follow-up (adjusted HR 5.65, 95% CI 3.07-10.41) or under steroid therapy during hospitalization (adjusted HR 5.14, 95% CI 2.08-12.75).Patients with stroke had a higher risk of subsequent SSNHL compared with patients without stroke. In particular, stroke patients within 1-year follow-up and those undergoing steroid therapy during hospitalization should be treated with the utmost caution, considering that the risk of SSNHL increases by more than 5-fold.

Intratympanic dexamethasone injection vs methylprednisolone for the treatment of refractory sudden sensorineural hearing loss

Background:

During the past years various drugs have been used for sudden sensorineural hearing loss (SSNHL) treatment including steroids that are shown to be beneficial. Directed delivery of high doses of steroids into the inner ear is suggested for its potential and known as intratympanic steroids therapy (IST). Despite the use of dexamethasone and methylprednisolone as the traditional treatments, there are still debates about the optimal dosage, preferred drug, and the route of administration.

Materials and Methods:

We performed a randomized clinical trial study in which 50 patients suffering from SSNHL and resistant to standard therapy were employed. Each patient took 0.5 ml methylprednisolone (40 mg/mg) along with bicarbonate or dexamethasone (4 mg/mL) through direct intratympanic injection. This method was performed and scheduled once every 2 days for three times only for the dexamethasone receiving group. Hearing test was carried out and the results were analyzed according to a four-frequency (0.5, 1.0, 2.0, 3.0 kHz) pure tone average (PTA) and Siegel's criteria.

Results:

According to Siegel's criteria, three out of 25 (12%) dexamethasone receiving patients were healed in 1 and 4 (16%), 9 (32%) were respectively recovered in Siegel's criteria 2, 3, and 9 (32%) showed no recovery. In the group receiving methylprednisolone, recovery was found in 6 (24%), 8 (32%), 7 (28%) patients in the Siegel's criteria 1, 2, 3, respectively, and in 4 (16%) patients no recovery was recorded. In methylprednisolone group, hearing was significantly improved compared to the dexamethasone group (P < 0.05). The general hearing improvement rate was 84% in methylprednisolone receiving patients showing a significantly higher improvement than 64% in the dexamethasone group.

Conclusions:

Topical intratympanic treatment with methylprednisolone is safe and an effective treatment approach for those SSNHL cases that are refractory to the common therapies by Dexamethasone.

Otoprotective effect of recombinant erythropoietin in a model of newborn hypoxic-ischemic encephalopathy

OBJECTIVE

The aim of this study is to test the hypotheses that central auditory pathology as well as inner ear pathology is contributing mechanisms to observed hypoxic-ischemic encephalopathy (HIE) induced hearing loss and that recombinant erythropoietin (rhEPO) will reduce this cellular pathology and attenuate hearing loss.

METHODS

Twenty-eight 7-day Wistar albino rat pups were divided into four groups: Control group (n=8) was given only intraperitoneal saline solution. Sham group (n=5) had only a midline neck incisions without carotid ligation under general anesthesia and administration of intraperitoneal saline solution. HIE group (n=8) and rhEPO treated group (n=7) were subjected to left common carotid artery ligation followed by 2.5h hypoxia exposure to a mixture of 8% oxygen and 92% pure nitrogen. HIE group was injected with intraperitoneal saline solution, while the rhEPO treated group received rhEPO 100 U/kg within the same volume as the saline-alone solution. At the end of the seventh week of age hearing (ABRs) was evaluated in response to clicks, 6 kHz and 8 kHz tone burst stimuli. Animals were sacrificed and both temporal lobes, cochleas and brainstems of the animals were collected. Tissue samples were evaluated with light microscopy, immunohistochemical studies, including TUNEL and caspase-3 stainings, and electron microscopy.

RESULTS

Hearing thresholds were elevated in HIE animals. In rhEPO treated animals, ABR values were similar to controls. HIE caused apoptotic changes in brainstem structures as shown by light microscopy and immunohistochemical methods. Apoptotic changes also were found within the organ of Corti, spiral ganglion cells and neurons of temporal lobe by electron microscopic investigation. In rhEPO animals many of these apoptotic changes were observed, but reduced compared to untreated animals.

CONCLUSIONS

Mechanisms underlying HIE-induced hearing loss are based on apoptosis in inner ear; however central auditory pathway pathology occurs as well, likely contributing to changes in auditory processing and perception of complex signals not reflected by the ABR threshold shifts. For both clinical and basic significance 'rhRPO' is found to reduce those effects.

Intratympanic steroids as primary initial treatment of idiopathic sudden sensorineural hearing loss. The Hospital Universitario Ramón y Cajal experience and review of the literature

The objective of this study was to determine the effectiveness, dosage, safety and comfort of intratympanic steroids as primary initial treatment of idiopathic sudden sensorineural hearing loss (ISSHL). Prospective nonrandomized clinical practice study was performed in Tertiary referral center university hospital. A total of 35 consecutive patients suffering from newly diagnosed sudden sensorineural hearing loss with mean pure-tone average thresholds of 81 ± 21 dB were treated. No previous therapy had been undertaken. Intratympanic steroid injection as primary initial treatment was administered during 2 weeks on a twice a week schedule, between 2010 and 2011. Treatment was started on average within 2 days of symptoms onset. Pre and post-treatment audiometric evaluations were analyzed on follow-up as well as tolerance of the procedure and possible adverse effects. 66-85 % of patients achieved successful treatment according to the different outcome criteria used to evaluate hearing improvement (Furuhashi criteria/improvement of ≥10 dB in pure-tone average). Mean post-treatment improvement regarding pure-tone average was 34 ± 21 dB. A 48 ± 43 % improvement in speech discrimination score was observed. Patients received an average of 18 mg of methylprednisolone per injection and a total dose of 72 mg per treatment cycle. No serious adverse effects were noted. Intratympanic steroid injection is an effective, safe and well-tolerated office based-procedure for the treatment of ISSHL as primary initial treatment that can avoid the potential adverse effects of systemic steroids. A higher dose, schedule of administration as well as standardization of hearing recovery criteria still need to be established.

Effect of intratympanic dexamethasone, memantine and piracetam on cellular apoptosis due to cisplatin ototoxicity

OBJECTIVE

This study aimed to contribute to the literature on the prevention and treatment of ototoxicity due to various drugs and chemicals.

MATERIAL AND METHODS

This study compared the histological effects of intratympanic dexamethasone, memantine and piracetam on cellular apoptosis due to cisplatin ototoxicity, in 36 rats.

RESULTS

Dexamethasone and memantine had significant effects on the stria vascularis, organ of Corti and spiral ganglion (p < 0.05). Although piracetam decreased the apoptosis rate, this effect was not statistically significant (p > 0.05).

CONCLUSION

Dexamethasone and memantine were found superior to piracetam in reducing apoptosis due to cisplatin ototoxicity. Further studies of this subject are needed, incorporating electron microscopy and auditory brainstem response testing.

Intratympanic steroid treatment for idiopathic sudden sensorineural hearing loss after failure of intravenous therapy

Purpose. The aim of this study is the investigation of the effectiveness of intratympanic steroids therapy (IST) in patients with idiopathic sudden sensorineural hearing loss (ISSHL) who had not responded to intravenous treatment, evaluating the overall hearing recovery and comparing the results with different variables. Materials and Methods. Our study consisted of 55 patients with refractory ISSHL who, at the end of 10 days of therapy with intravenous steroids, had puretone 4-frequency average (PTA) of worse than 30 dB. The patients received 0.5 mL of methylprednisolone by direct intratympanic injection. The procedure was carried out up to 7 times within a 20-days period. Statistical analysis was carried out. Results. Overall 29 patients (52.7%) showed improvement in PTA, 24 (43.8%) had no change in hearing, and 2 (3.5%) worsened. There was a significant statistical correlation between hearing recovery and time to onset of symptoms, severity of hearing loss and frequency of hearing loss. Conclusions. IST is an effective and safe therapy in sudden sensorineural hearing loss cases that are refractory to standard treatment. The earlier IST, the hearing losses less than 90 dB and the involvement of the low frequencies seem to influence positively the hearing recovery.

Effects of neuroactive steroids on cochlear hair cell death induced by gentamicin

As neuroactive steroids, sex steroid hormones have non-reproductive effects. We previously reported that 17β-estradiol (βE2) had protective effects against gentamicin (GM) ototoxicity in the cochlea. In the present study, we examined whether the protective action of βE2 on GM ototoxicity is mediated by the estrogen receptor (ER) and whether other estrogens (17α-estradiol (αE2), estrone (E1), and estriol (E3)) and other neuroactive steroids, dehydroepiandrosterone (DHEA) and progesterone (P), have similar protective effects. The basal turn of the organ of Corti was dissected from Sprague-Dawley rats and cultured in a medium containing 100 μM GM for 48h. The effects of βE2 and ICI 182,780, a selective ER antagonist, were examined. In addition, the effects of other estrogens, DHEA and P were tested using this culture system. Loss of outer hair cells induced by GM exposure was compared among groups. βE2 exhibited a protective effect against GM ototoxicity, but its protective effect was antagonized by ICI 182,780. αE2, E1, and E3 also protected hair cells against gentamicin ototoxicity. DHEA showed a protective effect; however, the addition of ICI 182,780 did not affect hair cell loss. P did not have any effect on GM-induced outer hair cell death. The present findings suggest that estrogens and DHEA are protective agents against GM ototoxicity. The results of the ER antagonist study also suggest that the protective action of βE2 is mediated via ER but that of DHEA is not related to its conversion to estrogen and binding to ER. Further studies on neuroactive steroids may lead to new insights regarding cochlear protection.

Ischemia-reperfusion injury of the cochlea: pharmacological strategies for cochlear protection and implications of glutamate and reactive oxygen species

A large amount of energy produced by active aerobic metabolism is necessary for the cochlea to maintain its function. This makes the cochlea vulnerable to blockade of cochlear blood flow and interruption of the oxygen supply. Although certain forms of human idiopathic sudden sensorineural hearing loss reportedly arise from ischemic injury, the pathological mechanism of cochlear ischemia-reperfusion injury has not been fully elucidated. Recent animal studies have shed light on the mechanisms of cochlear ischemia-reperfusion injury. It will help in the understanding of the pathology of cochlear ischemia-reperfusion injury to classify this injury into ischemic injury and reperfusion injury. Excitotoxicity, mainly observed during the ischemic period, aggravates the injury of primary auditory neurons. On the other hand, oxidative damage induced by hydroxyl radicals and nitric oxide enhances cochlear reperfusion injury. This article briefly summarizes the generation mechanisms of cochlear ischemia-reperfusion injury and potential therapeutic targets that could be developed for the effective management of this injury type.

Effects of systemic administration of methylprednisolone on residual hearing in an animal model of cochlear implantation

CONCLUSION

Delivery of intramuscular injection of methylprednisolone around the implantation surgery improved the hearing threshold shift induced by cochlear implantation.

OBJECTIVES

During electroacoustic cochlear implantation surgery, the residual hearing is not preserved in about 15% of cases. In this study, we tested the effects of intramuscular administration of methylprednisolone on the hearing loss induced by cochlear implantation in a model of guinea pig cochlear implantation.

METHODS

Eleven guinea pigs with normal hearing were implanted with a 254 μm diameter silicone array through a cochleostomy, and the effects on hearing of longstanding array insertion (21 days) were assessed. Six of the implanted animals received intramuscular administration of methylprednisolone. Auditory brainstem response recordings were performed before and up to 21 days after the cochlear implantation. CT scans were performed in some animals 1 month after implantation.

RESULTS

CT scans confirmed that the array was well positioned in tested animals. From days 3 to 21, a hearing loss of about 30 dB on all frequencies was observed in the implanted nontreated group. This hearing loss remained stable during the whole follow-up period. Compared with implanted nontreated animals, the hearing threshold shift decreased by 12 dB in animals treated with methylprednisolone.

[Glucocorticoid treatment for cochlear ischemic and acoustic injuries]

The effect of glucocorticoids on sensorineural hearing loss of sudden onset remains to be controversial although glucocorticoids have been used for treatment of sudden sensorineural hearing loss. We review recent findings about the effect of glucocorticoids on cochlear ischemic and acoustic injuries obtained from animal experiments. Systemically administered glucocorticoids penetrate the blood-cochlear barrier well. Glucocorticoids ameliorated the cochlear ischemic and acoustic injuries at a relatively wide range of doses, and they protect cochlear hair cells in these types of injury. The therapeutic actions of glucocorticoids in cochlear injuries were considered to be mediated via both genomic and non-genomic pathways. Based on the results obtained in acoustic injury, therapeutic time window of glucocorticoids is considered to be short after the onset of injury. These findings obtained from animal experiments are important in considering clinical usage of glucocorticoids for the treatment of sensorineural hearing loss.

Effects of NSAIDs on the Inner Ear: Possible Involvement in Cochlear Protection

Cyclooxygenase and lipoxygenase, two important enzymes involved in arachidonic acid metabolism, are major targets of non-steroidal anti-inflammatory drugs (NSAIDs). Recent investigations suggest that arachidonic cascades and their metabolites may be involved in maintaining inner ear functions. The excessive use of aspirin may cause tinnitus in humans and impairment of the outer hair cell functions in experimental animals. On the other hand, NSAIDs reportedly exhibit protective effects against various kinds of inner ear disorder. The present review summarizes the effects of NSAIDs on cochlear pathophysiology. NSAIDs are a useful ameliorative adjunct in the management of inner ear disorders.

Preventing hearing damage using topical dexamethasone during reversible cochlear ischemia: an animal model

HYPOTHESIS

Local application of dexamethasone to the round window (RW) niche prevents cochlear damage caused by local reversible ischemia.

BACKGROUND

Cochlear ischemia induced by internal auditory artery (IAA) compression/stretching is thought to cause postoperative sensory hearing loss after attempted hearing preservation removal of acoustic neuroma tumors. Dexamethasone administered to the RW niche traveling through the membrane to the cochlear fluids may prevent ischemic damage.

MATERIALS AND METHODS

Ten young albino rabbits were used for this study. Ischemic episodes were induced by compressing the IAA. Laser Doppler cochlear blood flow was measured using a probe positioned at the RW niche. Transtympanic electrocochleography was measured at 4, 8, and 12 kHz. In 5 test ears, dexamethasone was administered topically at the RW for approximately 50 minutes before the IAA compressions, whereas in 5 control ears, saline was applied in the same way. Each ear underwent one 10-minute IAA compression with a 60-minute postischemic period of transtympanic electrocochleography monitoring.

RESULTS

In both control- and dexamethasone-treated ears, ischemic episodes measured by Laser Doppler cochlear blood flow were comparable. Fifty minutes after IAA decompression, in dexamethasone-pretreated ears, cochlear microphonic and compound action potential amplitudes at all test frequencies were 10 to 15% less reduced than those in control ears. Compound action potential latencies in dexamethasone-pretreated ears resulted in shorter latency delay than in control ears.

CONCLUSION

The RW seems to be an efficacious route for the administration of dexamethasone into the inner ear. Dexamethasone showed a protective effect on cochlear function after local ischemia. Transtympanic electrocochleography was found to be a sufficient and effective tool in monitoring hearing.

Prednisolone prevents transient ischemia-induced cochlear damage in gerbils

CONCLUSIONS

Prednisolone protects against inner ear damage, even when administered after ischemic injury in Mongolian gerbils.

OBJECTIVE

The effect of prednisolone on ischemia-induced cochlear damage was investigated in Mongolian gerbils.

MATERIALS AND METHODS

The bilateral vertebral arteries were occluded for 15 min to transiently induce cochlear ischemia, followed by an intraperitoneal injection of prednisolone (1 mg/kg) or physiological saline (control). Sequential changes in hearing were evaluated by recording the auditory brainstem response (ABR) before and at 1, 4, and 7 days after treatment. In our histologic analysis, the numbers of dead and intact inner hair cells (IHCs) were counted in specimens stained with rhodamine-phalloidin.

RESULTS

In control animals, transient ischemia increased the ABR threshold (24.2 +/- 8.6 dB) within 7 days of treatment, whereas prednisolone-treated animals exhibited a threshold of 14.2 +/- 9.2 dB. Furthermore, the percent IHC loss at the basal turn of the cochlea was 26.5 +/- 11.4% in control animals compared with 5.3 +/- 3.0% in the prednisolone-treated group.

Intratympanic injection of dexamethasone: time course of inner ear distribution and conversion to its active form

HYPOTHESIS

Intratympanically injected dexamethasone 21-phosphate is converted to its active form dexamethasone in the inner ear and follows the distribution of the glucocorticoid receptor.

BACKGROUND

Although dexamethasone is routinely delivered intratympanically for hearing loss, we know little of its inner ear pharmacokinetics. Dexamethasone 21-phosphate is the pharmaceutical compound available for injection, but it must be converted to its biologically active form (dexamethasone) to bind to the glucocorticoid receptor. Therefore, the current study was conducted to determine the time course of dexamethasone 21-phosphate movement from the middle ear into the inner ear, its conversion to dexamethasone, and the distribution of both forms relative to the glucocorticoid receptor.

METHODS

BALB/c mice were injected intratympanically with the prodrug dexamethasone 21-phosphate and inner ears collected at postinjection times ranging from 5 minutes to 7 days. Ears were immunohistochemically stained for dexamethasone 21-phosphate, dexamethasone, and the glucocorticoid receptor.

RESULTS

Both forms of dexamethasone were seen in the inner ear within 15 minutes, reaching their highest staining intensity at 1 hour. Neither drug was seen after 24 hours. The strongest staining occurred in the spiral ligament, organ of Corti, spiral ganglion, and vestibular sensory epithelia. Distribution of the drug paralleled locations of the glucocorticoid receptor except in the stria vascularis marginal cells, which stained heavily for the receptor but not the drug.

CONCLUSION

Dexamethasone rapidly travels from the middle ear into the inner ear and converts to its active form. The drug distribution follows that of the glucocorticoid receptor. However, it probably has little impact on ear tissues after 24 hours.

Glucocorticoid impact on cochlear function and systemic side effects in autoimmune C3.MRL-Faslpr and normal C3H/HeJ mice

Glucocorticoids are effective in reversing hearing loss, but their severe side effects limit long term management of many ear disorders. A clearer understanding of these side effects is critical for prolonged therapeutic control of hearing and vestibular dysfunction. Therefore, this study characterized the impact of the glucocorticoid prednisolone on cochlear dysfunction and systemic organ systems in C3.MRL-Fas(lpr) autoimmune mice and their normal C3H/HeJ parent strain. Following 3 months of treatment, autoimmune mice had better auditory thresholds and improved hematocrits, anti-nuclear antibodies, and immune complexes. Steroid treatment also lowered body and spleen weights, both of which rise with systemic autoimmune disease. Steroid treatment of the normal C3H/HeJ mice significantly elevated their blood hematocrits and lowered their body and spleen weights to abnormal levels. Thus, systemic autoimmune disease and its related hearing loss in C3.MRL-Fas(lpr) mice are steroid-responsive, but normal hemopoiesis and organ functions can be significantly compromised. This mouse model may be useful for studies of the detrimental side effects of steroid treatments for hearing loss.

Mechanisms of noise-induced hearing loss indicate multiple methods of prevention

Recent research has shown the essential role of reduced blood flow and free radical formation in the cochlea in noise-induced hearing loss (NIHL). The amount, distribution, and time course of free radical formation have been defined, including a clinically significant late formation 7-10 days following noise exposure, and one mechanism underlying noise-induced reduction in cochlear blood flow has finally been identified. These new insights have led to the formulation of new hypotheses regarding the molecular mechanisms of NIHL; and, from these, we have identified interventions that prevent NIHL, even with treatment onset delayed up to 3 days post-noise. It is essential to now assess the additive effects of agents intervening at different points in the cell death pathway to optimize treatment efficacy. Finding safe and effective interventions that attenuate NIHL will provide a compelling scientific rationale to justify human trials to eliminate this single major cause of acquired hearing loss.

Intratympanic Dexamethasone for Sudden Sensorineural Hearing Loss After Failure of Systemic Therapy

OBJECTIVE

Intratympanic steroids are increasingly used in the treatment of inner ear disorders, especially in patients with sudden sensorineural hearing loss (SNHL) who have failed systemic therapy. We reviewed our experience with intratympanic steroids in the treatment of patients with sudden SNHL to determine overall success, morbidity, and prognostic factors.

HYPOTHESIS

Intratympanic steroids have minimal morbidity and the potential to have a positive effect on hearing recovery in patients with sudden SNHL who have failed systemic therapy.

STUDY DESIGN

The authors conducted a retrospective review.

METHODS

Patients presenting with sudden SNHL defined as a rapid decline in hearing over 3 days or less affecting 3 or more frequencies by 30 dB or greater who underwent intratympanic steroids therapy (24 mg/mL dexamethasone) were reviewed. Excluded were patients with Meniere disease, retrocochlear disease, autoimmune HL, trauma, fluctuating HL, radiation-induced HL, noise-induced HL, or any other identifiable etiology for sudden HL. Patients who showed signs of fluctuation of hearing after injection were excluded. Pretreatment and posttreatment audiometric evaluations including pure-tone average (PTA) and speech reception threshold (SRT) were analyzed. Patient variables as they related to recovery were studied and included patient age, time to onset of therapy, status of the contralateral ear, presence of diabetes, severity of HL, and presence of associated symptoms (tinnitus, vertigo). A 20-dB gain in PTA or a 20% improvement in SDS was considered significant.

RESULTS

: Forty patients fit the criteria for inclusion in the study. The mean age of the patients was 54.8 years with a range from 17 to 84 years of age. Overall, 40% (n = 16) showed any improvement in PTA or SDS. Fourteen (35%) men and 26 (65%) women were included. Using the criteria of 20-dB improvement in PTA or 20% improvement in SDS for success, 27.5% (n = 11) showed improvement. The mean number of days from onset of symptoms to intratympanic therapy was 40 days with a range of 7 days to 310 days. A statistically significant difference was noted in those patients who received earlier injection (P = .0008, rank sum test). No patient receiving intratympanic dexamethasone after 36 days recovered hearing using 20-dB PTA decrease or a 20% increase in discrimination as criteria for recovery. Twelve percent (n = 5) of patients in the study had diabetes with 20% recovering after intratympanic dexamethasone (not significantly different from nondiabetics at 28.6%, Fisher exact test, P = 1.0). Comparison to other studies that used differing steroid type, concentration, dosing schedule, inclusion criteria, and criteria for success revealed, in many instances, a similar overall recovery rate.

CONCLUSIONS

Difficulty in proving efficacy of a single modality is present in all studies on SNHL secondary to multiple treatment protocols, variable rates of recovery, and a high rate of spontaneous recovery. Forty percent of patients showed some improvement in SDS or PTA after treatment failure. When criteria of 20-dB PTA or 20% is considered to define improvement, the recovery rate was 27.5%. Modest improvement is seen with the current protocol of a single intratympanic steroid injection of 24 mg/mL dexamethasone in patients who failed systemic therapy. Dramatic hearing recovery in treatment failures was rarely encountered. No patient showed significant benefit from intratympanic steroids after 36 days when using this protocol for idiopathic sudden SNHL. If patients injected after 6 weeks are excluded from the study, the improvement rate increases from 26.9% to 39.3%. Earlier intratympanic injection had a significant impact on hearing recovery, although with any therapeutic intervention for sudden SNHL, early success may be attributed to natural history. If we further exclude seven patients treated with intratympanic steroids within 2 weeks of the onset of symptoms (i.e., study only those patients treated with intratympanic dexamethasone between 2 and 6 weeks after onset of symptoms), still, 26% improved by 20 dB or 20% SDS. The recovery rates after initial systemic failure are higher than would be expected in this treatment failure group given our control group (9.1%) and literature review. These findings indicate a positive effect from steroid perfusion in this patient population.

Therapeutic efficacy of intra-cochlear administration of methylprednisolone after acoustic trauma caused by gunshot noise in guinea pigs

The therapeutic efficacy of cochlear infusion of methylprednisolone (MP) after an impulse noise trauma (170dB SPL peak) was evaluated in guinea pigs. The compound action potential threshold shifts were measured over a 14 days recovery period after the gunshot exposure. For each animal, one of the cochlea was perfused directly into the scala tympani with MP during 7 days via a mini-osmotic pump, whereas the other cochlea was not pump-implanted. The functional study of hearing was supplemented by histological analysis. Forty eight hours after the trauma, significant differences between auditory threshold shifts in the implanted and non-implanted ears were observed for frequencies above 8kHz. At day 7, the difference was significant for only one frequency and no difference was observed after 14 days recovery. Cochleograms showed that the hair cell losses were significantly lower in the MP treated ears. This work indicates that direct infusion of MP into perilymphatic space accelerates hearing recovery, reduces hair cell losses after impulse noise trauma but does not limit permanent threshold shifts.

Enhanced biosynthesis of glutathione in the spiral ganglion of the cochlea after in vivo treatment with dexamethasone in mice

Glucocorticoids have been widely used as a therapeutic drug for sudden sensorineural hearing loss. However, very little is known about the mechanism(s) underlying the protective effect of glucocorticoids against hearing loss. As an approach toward elucidating the mechanism(s), we evaluated the effects of dexamethasone (DEX) treatment on the biosynthesis of GSH in the mouse cochlea in vivo. The systemic administration of DEX led to a significant increase in the total GSH level in the cochlea 2 to 24 h later. This DEX-induced increase in GSH occurred selectively in the spiral ganglion, but not significantly in the lateral wall tissues or in the organ of Corti. Furthermore, RT-PCR analysis revealed that DEX treatment resulted in enhanced expression of gamma-glutamylcysteine synthetase (gamma-GCS), which is the rate-limiting enzyme for de novo GSH synthesis, 1 to 24 h after the treatment. In addition to enhancing GSH biosynthesis, DEX treatment was effective in reducing lipid peroxidation in the cochlea. Taken together, DEX has the ability to facilitate GSH biosynthesis through enhanced expression of gamma-GCS in the cochlear spiral ganglion.

Protective effects of glucocorticoids on ischemia-reperfusion injury of outer hair cells

OBJECTIVE

This animal study aimed to investigate effects of glucocorticoids on the functional recovery of outer hair cells (OHCs) after transient ischemia.

METHODS

Distortion-product otoacoustic emission (DPOAE) was examined before, during, and after transient cochlear ischemia of 30 minutes using albino guinea pigs.

RESULTS

DPOAE decreased to noise level during ischemia. On recirculation, DPOAE initially recovered with time until 20 minutes after the onset of reperfusion, but thereafter, the DPOAE level gradually decreased toward the noise level in the control animals. Prednisolone and methylprednisolone significantly improved the DPOAE level 60 minutes after the onset of reperfusion.

CONCLUSIONS

The present findings suggest that glucocorticoids possess protective effects against ischemia-reperfusion injury of OHCs.

Effect of Corticosteroids or Diuretics in Low-Tone Sensorineural Hearing Loss

OBJECTIVES

We retrospectively analyzed 225 patients with acute low-tone sensorineural hearing loss (ALSHL), comparing the effectiveness of corticosteroid and diuretic therapy, and also determining the factors affecting hearing recovery.

DESIGN

Retrospective clinical record review.

METHODS

Multivariate logistic regression analysis.

RESULTS

Analyses identified unfavorable factors such as aging, late initiation of treatment, and pretreatment pure-tone hearing thresholds at three lower frequencies adding up to 95 dB and more. Multivariate logistic regression analysis indicated a significantly greater improvement in hearing in patients treated with corticosteroids at high initial and total doses than in those treated with vitamin B12 and ATP without adding corticosteroids. In 145 patients treated with corticosteroids, multivariate logistic regression analysis showed a trend toward greater improvement with high initial and total doses than with low doses.

CONCLUSION

Corticosteroids should be changed from low to high doses within 7 days after onset of ALSHL, if low doses are failing.

Protective effect of calcineurin inhibitors on acoustic injury of the cochlea

This study examined the effect of immunosuppressants, cyclosporin A, FK506 and rapamycin on functional recovery of the cochlea after acoustic overexposure, in guinea pigs and mice. Thirty guinea pigs were exposed to a 2 kHz pure tone at 120 dB SPL for 10 min. The compound action potential threshold shift induced by acoustic overexposure was examined. Twenty-five mice were exposed to a 4 kHz pure tone at 128 dB SPL for 4h. Auditory brainstem response was used to examine the hearing threshold shift. In both the guinea pig and mouse experiments, cyclosporin A and FK506, intraperitonally given just before acoustic overexposure, significantly decreased the hearing threshold shift one or two weeks after acoustic overexposure. However, neither rapamycin nor the FK506 and rapamycin combined treatment groups showed improvement of the threshold shift. The present findings suggest that these two calcineurin inhibitors have a protective effect against acoustic injury of the cochlea, whereas the non-calcineurin inhibitor, rapamycin, not only has no effect against acoustic injury, but rather blocked the effect of FK506. This indicated a possible role of calcineurin against acoustic injury.

Surdités brusques idiopathiques

Idiopathic Sudden Sensorineural Hearing Loss (ISSHL) remains one of the major unsolved otologic emergencies. It is characterized by the onset of an unilateral sensorineural hearing loss developing within 24 hours, and averaging on pure tone audiogram at least 30 dB HL for three subsequent octave steps, with no marked vestibular symptoms and no identifiable cause. ISSHL is a syndrome covering several heterogeneous entities resulting from different pathogenetic mechanisms. At this time, the audiogram is the unique tool which may help clinicians to identify these entities and provide a classification based on 5 types of hearing loss. Numerous experimental and clinical studies have investigated the mechanisms by which infectious, ischemic, mechanic or immunologic insults may induce cochlear dysfunction. However, extrapolation to humans and rationale therapeutic approaches to ISSHL remain uncertain. SSHL being a diagnosis of exclusion, retrocochlear and neurologic etiologies should be eliminated. No argument allows to consider ISSHL a therapeutic emergency. More precisely, the experimental data presently available on cochlear physiology suggests that a treatment could have some chance to be effective if undertaken within minutes following the onset of ISSHL, a condition never encountered in daily practice. Conversely, it is not justifiable to impute the absence of hearing recovery to a delay in therapy. The various therapeutic strategies currently recommended are highly empirical and should be questionned in terms of cost-effectiveness, the most common being high-dose corticosteroids. New investigation tests are required for improving our approach to ISSHL.

Intratympanic treatment of hearing loss with novel and traditional agents

As knowledge of the cellular and molecular pathophysiology behind otopathologies expands, the possibility exists of preventing sensorineural hearing loss and perhaps reversing the loss. Cellular and molecular mechanisms seem to be similar in hearing loss secondary to aging, drug ototoxicity, noise, or other mechanisms. A final common pathway may hinge upon apoptosis. It is likely that anti-apoptotic factors will increasingly be realized as an important intervention strategy for sensorineural hearing loss. Furthermore, it is also possible that mounting a staged attack at the various regions in the pathway leading to cellular damage using a combination of several protective substances such as steroids, antioxidants, neurotrophic factors, anti-apoptotic compounds, and mitochondrial enhancers may prevent hearing loss and even reverse it in some situations. This article has presented some of the molecular and cellular mechanisms for hearing loss and potential ways of treating them. In theory, the delivery of these medications to the inner ear transtympanically would decrease systemic side effects and be more target specific. Because most of the studies conducted to date have been animal studies, randomized, double-blind, placebo-controlled clinical trials would be necessary before the use of these therapies becomes common practice.

Intratympanic dexamethasone with hyaluronic acid in the treatment of idiopathic sudden sensorineural hearing loss after failure of intravenous steroid and vasoactive therapy

The purpose of this prospective study was to test whether intratympanic application of dexamethasone/hyaluronic acid improves hearing outcome in patients with pantonal idiopathic sudden sensorineural hearing loss (ISSHL), in patients with sudden deafness or sudden profound SHL and in patients with predominant high-frequency ISSHL who are refractory to intravenous steroid and vasoactive therapy. The study took place in an academic tertiary referral hospital involving 21 patients with pantonal ISSHL, 10 patients with sudden deafness or sudden profound SHL and 9 patients with a high-frequency ISSHL. Intratympanic dexamethasone/hyaluronic acid was administered in the affected ear. Hearing was evaluated by means of standard pure-tone audiometry. The differences between pure-tone hearing thresholds by air conduction before intravenous therapy and before the beginning of the intratympanic therapy, as well as before and after intratympanic therapy, were calculated. Statistical analysis was performed by means of the Wilcoxon's test for paired samples. Intratympanic injection of dexamethasone/hyaluronic acid results in a significant global (pantonal) improvement in hearing in patients with pantonal ISSHL. It also effects improvement in hearing at selected frequencies (namely at 1.5 and 3 kHz) in patients with a predominant high-frequency ISSHL and at selected frequencies (namely at 0.5, 0.75 and 1 kHz) in patients with sudden deafness or sudden profound SHL. Neither systemic nor local side effects were observed. Intratympanic administration of dexamethasone/hyaluronic acid provides a safe and efficacious therapeutic option for the treatment of patients with pantonal and high-frequency ISSHL who don't respond to intravenous steroid and vasoactive therapy.