Effect of intratympanic steroid injection on hearing loss and tinnitus in sudden sensorineural hearing loss

Introduction

Sudden sensorineural hearing loss (SSNHL) is defined as a rapid loss of more than 30 decibels (dB) of sensorineural hearing across three or more consecutive frequencies within a three-day period (1). To prevent irreversible auditory damage, prompt medical intervention is crucial (2). The incidence of SSNHL ranges from 2 to 30 cases per 100,000 adults annually, with no clear gender predilection. It most commonly affects individuals in their fifth or sixth decade of life (3).

The World Health Organization (WHO) classifies hearing loss into four categories based on severity. Slight hearing impairment: 26–39 dB. Moderate hearing impairment: 40–59 dB. Severe hearing impairment: 60–79 dB. Profound hearing impairment: ≥80 dB (4).

In addition to hearing loss, SSNHL may also induce tinnitus, believed to result from central neural alterations at higher auditory processing levels (5). Various standardized inventories are available to classify the severity of tinnitus (6).

Although the exact pathophysiology of SSNHL in humans remains unclear, potential contributing factors include viral infections, vascular compromise, autoimmune disorders, trauma, congenital inner ear malformations, smoking, severe stress, and central nervous system disorders such as acoustic tumors (7,8). Despite reports that 32% to 65% of patients may recover spontaneously, early treatment remains critically important (9).

However, treatment strategies for SSNHL are nearly as varied as its suspected etiologies. Proposed therapeutic agents include anti-inflammatory drugs, antimicrobials, vasodilators, vasoactive substances, hyperbaric oxygen, and other interventions (10). Among these, systemic corticosteroids are the most commonly used for idiopathic SSNHL, despite the significant risk of adverse effects and contraindications associated with long-term use. As a result, local steroid delivery—particularly intratympanic steroid (ITS) therapy—has gained increasing popularity over the last decade in otologic practice (11).

While the precise mechanism of steroid action in the inner ear is not fully understood, it is hypothesized that they improve hearing by reducing inflammation and oedema in the cochlea, with reported efficacy rates ranging from 49% to 89% (12). Despite their systemic bioavailability, the use of oral steroids is still debated due to their side effect profile. In contrast, ITS offers a promising alternative by achieving high steroid concentrations in the inner ear through diffusion via the round window membrane, while minimizing systemic exposure (13).

ITSs can be administered either as a primary therapy or as a salvage option following unsuccessful systemic treatment (14). When used as salvage therapy, ITS is generally recommended within two to six weeks of symptom onset (2). A key advantage of intratympanic administration over systemic delivery is that cochlear perilymph concentrations are approximately 100 times higher with the former. Despite this, intratympanic injections are not without potential risks, including tympanic membrane perforation and increased susceptibility to infection; however, reported complications remain relatively rare (15,16).

The true efficacy of steroids in treating idiopathic sudden sensorineural hearing loss (ISSHL) is still under investigation. Therefore, the objective of this study is to evaluate the effectiveness of ITS injections, particularly in improving hearing loss and tinnitus. Although ITS is commonly used as salvage therapy after systemic treatment failure, there is limited data on its role as a primary treatment or in combination therapy. This study explores outcomes in both treatment scenarios.

Methods

Study design

A prospective observational cohort study was conducted at the Department of Otorhinolaryngology Head and Neck Surgery, Faruk Medical City (FMC) Hospital, and the first authors private clinic from January 1st, 2020, to September 30, 2022, of patients diagnosed with SSNHL. All patients provided written informed consent. The evaluation of sudden hearing loss was conducted in accordance with the criteria established by the American Academy of Otolaryngology Head and Neck Surgery (AAO-HNS) (17). The diagnostic criteria for the disease were determined by clinical examination (Rinne and Weber tests) and by pure tone audiometry (PTA); through the PTA, the level of sensorineural hearing loss was classified through the WHO classification (4). The patients also performed a Tinnitus Handicap Inventory (THI) test both before receiving treatment and on the final follow-up visit (18). Residency status was classified as either urban or rural based on national and regional definitions. Urban residence referred to living in a city or town with population size and infrastructure consistent with official national classifications, while rural residence denoted living in non-urban settings such as villages or remote areas, as documented in the patient’s demographic information. The diagnosis of diabetes mellitus and hypertension was established according to the WHO criteria (19,20). This study is reported according to the STROBE reporting guidelines (available at https://www.theajo.com/article/view/10.21037/ajo-25-7/rc). Furthermore, the study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the University of Sulaimani, College of Medicine. Ethical code: 140 Date: 22/6/2021 Meeting Number: 15. Patient confidentiality was maintained by anonymizing data, and individual consent was waived for this retrospective analysis.

Eligibility criteria

Inclusion criteria: (I) adult patients (≥16 years) diagnosed with SSNHL; (II) SSNHL patients who have or have not received prior treatment; (III) SSNHL patients with or without other systemic diseases.

Exclusion criteria: MRI-confirmed central causes or prior ear surgeries.

The intervention

In patients with no prior drug use, ITS injections were used as primary treatment whereas for other patients that could not take systemic steroids (due to systemic diseases) and those with previously failed therapies, it was used as a salvage treatment. Nevertheless, all patients received ITS injections.

Patients received six intratympanic injections of steroids in 6 consecutive days.

The patients were placed in a supine position with their head turned to the healthy side. All the procedures were performed under a microscopic view. The ear canal was anesthetized by putting a cotton pledget soaked in 10% lidocaine and left in the ear canal for 10 minutes. Then, a 2 mL dexamethasone ampoule (8 mg in 2 mL) was injected using a 2 mL syringe attached to a 22-gauge spinal needle. In general, 1 mL of dexamethasone was enough to fill the tympanic cavity which was injected into the lower posteroinferior quadrant of the tympanic membrane in the supine position. After injection, the patients remained in a position with their treated ear upwards for about 15 minutes to facilitate passage of steroids across the round window membrane and they were also instructed to refrain from swallowing or talking. Some patients remained in this position for up to 30 minutes due to symptoms such as dizziness and vertigo.

Oral prednisolone 20 mg were provided in patients who did not have any contraindications (diabetes and hypertension), and they were given in a tapering manner of three times a day for three days, two times a day for three days, and finally, once a day for three days. In addition, oral betahistine 16 mg tablets were prescribed to all patients, once a day for a month.

Patients were monitored clinically and audiologically for three months, with weekly reviews. A weekly follow-up was carried out. The patients had four different outcomes, according to the Siegel’s Classification Criteria (21).

• Complete recovery, final PTA is less than 25 dB;
• Partial recovery, PTA gain is more than 15 dB and final PTA is between 25 and 45 dB;
• Slight recovery, PTA gain is more than 15 dB and final PTA is more than 45 dB;
• No improvement, PTA gain is less than 15 dB.

According to the literature, improvement is assessed by comparing results to pre-SSNHL PTAs, and complete (full) recovery is within 10 dB of initial PTA, however, in this study, as none of the patients had prior PTAs, the results of the treated ear were compared to the “normal” contralateral ear, this has also been done by other clinicians in the literature (22).

All patients included in this study were required to complete the THI questionnaire both prior to receiving treatment for SSNHL and at their final follow-up visit. The THI is a validated, self-reported questionnaire consisting of 25 items designed to assess the functional, emotional, and huge impact of tinnitus on a patient’s daily life. It provides a quantitative measure of tinnitus-related handicap and is widely used in both clinical and research settings to monitor treatment outcomes (18). The THI was displayed as THI improvement, and the treatment was effective in reducing tinnitus when the THI score reduced by 10 or more (23).

Data administration and statistical analysis

Preliminary results were obtained. Patients’ socio-demographic data, including age and audiological measurements, and the percentage of categorical variables were calculated. A Kolmogorov-Smirnov test was used to examine the normal distribution of the collected data. For normally distributed data, an independent-sample T test was used to examine the relationship between two continuous variables. A chi-squared test was used to examine the relationship between categorical. The level of statistical significance was set at P value of less than 0.05. Data analysis was carried out using SPSS version 22.0 (SPSS Inc., Chicago, IL, USA).

Results

This study included 48 patients, of whom 25 (52.1%) were female and 23 (47.9%) were male. The participants’ ages ranged from 16 to 82 years, with a mean age of 45.4±15.5 years. All patients presented with unilateral hearing loss and tinnitus, equally distributed between the right (n=24, 50.0%) and left (n=24, 50.0%) ears. Only one patient (2.1%) had a history of prior otologic surgery.

Among the study population, 27 individuals (56.2%) were over 45 years of age. Most participants were unemployed and resided in urban areas. Additionally, 10 patients (20.8%) had comorbid conditions, including diabetes mellitus, hypertension, or both (Table 1).

Twenty-two patients (45.8%) presented to the clinic between two weeks and one month after the onset of hearing loss and/or tinnitus. Eighteen patients (37.5%) had received treatment at other centers prior to presenting to the first author’s clinic; among them, 11 (61.1%) had been prescribed oral prednisolone. On clinical examination, all patients had positive Rinne tests and Weber tests lateralized to the unaffected ear. PTA revealed profound hearing loss in 17 patients (35.4%). In addition to PTA, all patients completed the THI questionnaire both before treatment initiation and at their final follow-up visit. Of the 48 patients, 38 (79.2%) had mild to moderate tinnitus based on their pre-treatment THI scores (Table 2).

All patients received ITS injections as previously described. Regarding oral medications, 36 patients (75.0%) were prescribed both betahistine and prednisolone, while the remaining 12 patients (25.0%) received betahistine alone due to comorbidities—specifically diabetes mellitus and/or hypertension—that contraindicated the use of oral corticosteroids (Table 3).

Based on Siegel’s classification, 16 patients (33.3%) achieved full recovery, defined as PTA thresholds identical to those of the contralateral ear. In contrast, only four patients (8.3%) showed no recovery. Tinnitus treatment was considered effective if the THI score improved by 10 points or more; otherwise, the treatment was deemed ineffective. Using this criterion (21), 38 patients (79.2%) demonstrated clinically significant improvement in tinnitus symptoms (Table 4).

Statistical associations between variables are presented in Tables 5-7. Table 5 evaluates the relationship between age, symptom duration, and occupation in relation to hearing outcomes. All four patients who experienced no recovery were aged between 35 and 54 years. These individuals were all unemployed, whereas all self-employed patients achieved complete recovery. Additionally, both patients who presented to the clinic more than three months after symptom onset showed no recovery, while all six patients who sought care within 1 week experienced complete recovery. These findings highlight the potential importance of early intervention in improving hearing outcomes.

A Chi-square test of independence revealed a statistically significant association between age group and hearing recovery outcome (χ²=36.34, df=18, P=0.006), with a moderate effect size (Cramér’s V=0.50; 95% CI: 0.04–0.26). In contrast, no significant association was observed between occupation and recovery outcome (P=0.183). However, symptom duration was highly significantly associated with recovery outcome (χ²=41.45, df=12, P<0.001), with a moderate-to-strong effect size (Cramér’s V=0.54; 95% CI: 0.04–0.26).

Table 6 examines the association between sex and recovery outcomes. Among the 10 patients for whom the intervention was ineffective in managing tinnitus, 8 (80.0%) were female and 2 (20.0%) were male. A Chi-square test of independence revealed a statistically significant association between sex and recovery outcome (χ²=6.2, P=0.013). To further quantify this relationship, an odds ratio (OR) was calculated, indicating that males were 4.94 times more likely to experience recovery compared to females. However, the 95% confidence interval for the OR ranged from 0.92 to 26.41, and the association did not reach statistical significance when assessed using Fisher’s exact test (P=0.075).

Finally, Table 7 examines the relationship between improvements in the THI and hearing outcomes—based on Siegel’s classification—in relation to previous treatment history. The results suggest that the treatment protocol used in this study produced comparable effects in both previously treated and untreated groups. A Chi-square test of independence revealed no significant association between prior treatment and tinnitus severity, as measured by the THI (P=0.582). Similarly, no significant association was observed between prior treatment and hearing outcome (P=0.090).

Discussion

SSNHL is widely recognized as an otological emergency, often presenting abruptly with unilateral hearing impairment, and frequently accompanied by tinnitus (5). Its aetiology remains unclear, with a broad differential diagnosis and no universally accepted treatment protocol, creating challenges for both clinicians and patients (1). While hearing recovery has traditionally been the primary measure of treatment success, recent literature emphasizes the importance of addressing tinnitus as a significant and disabling symptom (5,24). In this prospective study, we evaluated 48 patients presenting with unilateral SSNHL and tinnitus, all of whom received ITS injections and Betahistine, with 75% additionally prescribed oral prednisolone. Hyperbaric oxygen therapy (HBOT), a treatment option cited in existing guidelines, was not employed due to its unavailability in the study region (25). Betahistine improves blood flow to the cochlear and we postulate this may be a useful adjunct in the setting of SSNHL (26). Using Siegel’s classification, we observed that 33.3% of patients achieved complete hearing recovery, and only 8.3% had no improvement. Additionally, 79.2% of patients reported clinically significant improvement in tinnitus severity based on the THI. Early intervention, particularly within the first week of symptom onset, and younger age were both significantly associated with favourable hearing outcomes. Although female patients showed a trend toward lower recovery rates, the association did not reach statistical significance. Prior treatment at other centres did not significantly alter outcomes, suggesting the consistent efficacy of the treatment protocol applied in this study.

In our study, we observed that 33% of patients achieved complete recovery according to Siegel’s criteria. This contrasts with a study using HBOT, where only 19% of patients experienced complete recovery. However, in that study, all patients had previously failed steroid therapy, whereas only 23% of our patients had received prior oral prednisolone treatment (22). In another HBOT-based study, the complete recovery rate was reported at 8.5%, despite only 6.8% of their patients presenting more than 14 days after symptom onset. In contrast, more than 77% of our patients presented after 2 weeks, yet we achieved a higher rate of recovery (27). When comparing our findings with other studies that employed steroid therapy, one study involving 110 patients with SSNHL reported an 18% complete recovery rate. This is broadly comparable to our results, particularly considering that approximately 45.5% of their patients had failed previous oral steroid treatment, compared to 37.5% in our cohort. Additionally, their treatment protocol involved initial intravenous dexamethasone followed by tapered oral methylprednisolone, in contrast to our standardized intratympanic approach (28).

With respect to tinnitus outcomes, we found a 79.2% effectiveness rate in THI score reduction. This aligns closely with the findings of Ding et al., who reported a 79.13% effectiveness rate after treating 230 patients with a combination of HBOT, steroids (intratympanic for patients with diabetes or hypertension, intravenous for others), Ginkgo biloba, and lidocaine (23). Notably, we achieved comparable results without employing HBOT. Our study used Betahistine as an adjunct. Furthermore, our data demonstrated statistically significant associations between improved hearing recovery and factors such as younger age, employment status (as a proxy for access to care), and shorter symptom duration prior to treatment initiation. These findings are consistent with previously published literature highlighting the importance of early intervention and patient demographics in predicting recovery outcomes in SSNHL (23,29).

This study has several limitations that warrant consideration. First, the absence of a control group receiving either placebo, or no treatment limits the ability to draw definitive conclusions about the intervention’s efficacy; however, such a design was precluded by local ethical guidelines and regulatory constraints. Second, while a comparative analysis involving patients treated with HBOT would have been valuable, this modality was not accessible within our region during the study period. Additionally, although all patients received ITS therapy, 75% were also prescribed oral corticosteroids. Given the systemic absorption potential of ITSs and the frequent use of combination therapy, caution must be exercised when attributing treatment outcomes to a single modality. The subgroup receiving ITS therapy alone was relatively small, reducing the statistical power for subgroup comparisons. Furthermore, the study was not blinded, introducing the potential for observation and reporting bias. Adverse events were not systematically recorded, limiting the ability to assess the safety profile of the treatment regimen. These limitations highlight the importance of conducting larger, rigorously designed, multi-centre randomized controlled trials with standardized treatment protocols and safety monitoring to validate our findings and improve generalizability.

Despite extensive research and numerous published studies on sudden SSNHL, a consensus on a standardized treatment protocol remains lacking. This study revisited the topic with the goal of contributing clear and clinically applicable evidence, recognizing that many existing systematic reviews and meta-analyses are limited by methodological heterogeneity. As advanced treatment modalities—such as HBOT and combination pharmacologic regimens—become increasingly accessible in well-resourced settings, the demand for robust, standardized, and statistically sound clinical data becomes more urgent. Future research should evaluate whether a reduced number of ITS injections can yield comparable outcomes, potentially enhancing patient adherence and alleviating strain on healthcare resources. Additionally, the use of Betahistine as an adjunctive therapy in SSNHL warrants systematic investigation through controlled trials. To progress toward internationally endorsed, evidence-based treatment guidelines, upcoming investigations must emphasize protocol consistency and adhere to rigorous methodological standards across diverse clinical settings.

Conclusions

In summary, SSNHL continues to pose a significant clinical challenge due to its unpredictable onset, unclear aetiology, and variable treatment responses. While innovation and exploration of novel therapies are valuable, the development of a unified, evidence-based treatment protocol is imperative. The findings of this study suggest that ITS injections, particularly when used in conjunction with oral corticosteroids and Betahistine, may offer a promising approach for managing SSNHL. Our six-session ITS protocol demonstrated favourable auditory and tinnitus-related outcomes. However, the optimal frequency and duration of ITS administration remain to be clearly defined. Rigorous, well-powered randomized controlled trials are essential to delineate the specific contributions of each therapeutic component and to inform the development of globally applicable treatment guidelines.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://www.theajo.com/article/view/10.21037/ajo-25-7/rc

Data Sharing Statement: Available at https://www.theajo.com/article/view/10.21037/ajo-25-7/dss

Peer Review File: Available at https://www.theajo.com/article/view/10.21037/ajo-25-7/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://www.theajo.com/article/view/10.21037/ajo-25-7/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the University of Sulaimani, College of Medicine. Ethical code: 140 Date: 22/6/2021 Meeting Number: 15. Patient confidentiality was maintained by anonymizing data, and individual consent was waived for this retrospective analysis.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical practice guideline: sudden hearing loss. Otolaryngol Head Neck Surg 2012;146:S1-35. [Crossref] [PubMed]
2. Chandrasekhar SS, Tsai Do BS, Schwartz SR, et al. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol Head Neck Surg 2019;161:S1-45. [Crossref] [PubMed]
3. Singh A, Kumar Irugu DV. Sudden sensorineural hearing loss - A contemporary review of management issues. J Otol 2020;15:67-73. [Crossref] [PubMed]
4. Report of the informal working group on prevention of deafness and hearing impairment programme planning, Geneva, 18-21 June 1991. Geneva: World Health Organization; 1991. Available online: http://www.who.int/iris/handle/10665/58839 [cited 2019 Apr 1].
5. Mokhatrish M, Baek W, Nam GS, et al. Tinnitus characteristics in patients with idiopathic sudden sensorineural hearing loss and acute tinnitus. Laryngoscope Investig Otolaryngol 2023;8:1384-9. [Crossref] [PubMed]
6. Tinnitus in Sudden Sensorineural Hearing Loss. Tinnitustedavisi.net. 2015 [cited 2025 Jan 7]. Available online: https://www.tinnitustedavisi.net/tinnitus-in-sudden-sensorineural-hearing-loss
7. Fernández M, Cuesta M, Sanz R, et al. Comparison of Tinnitus Handicap Inventory and Tinnitus Functional Index as Treatment Outcomes. Audiol Res 2022;13:23-31. [Crossref] [PubMed]
8. Linthicum FH Jr, Doherty J, Berliner KI. Idiopathic sudden sensorineural hearing loss: vascular or viral? Otolaryngol Head Neck Surg 2013;149:914-7. [Crossref] [PubMed]
9. Lloyd SK. Sudden sensorineural hearing loss: early diagnosis improves outcome. Br J Gen Pract 2013;63:e592-4. [Crossref] [PubMed]
10. Lee HA, Chung JH. Contemporary Review of Idiopathic Sudden Sensorineural Hearing Loss: Management and Prognosis. J Audiol Otol 2024;28:10-7. [Crossref] [PubMed]
11. El Sabbagh NG, Sewitch MJ, Bezdjian A, et al. Intratympanic dexamethasone in sudden sensorineural hearing loss: A systematic review and meta-analysis. Laryngoscope 2017;127:1897-908. [Crossref] [PubMed]
12. Li H, Feng G, Wang H, et al. Intratympanic steroid therapy as a salvage treatment for sudden sensorineural hearing loss after failure of conventional therapy: a meta-analysis of randomized, controlled trials. Clin Ther 2015;37:178-87. [Crossref] [PubMed]
13. Qiang Q, Wu X, Yang T, et al. A comparison between systemic and intratympanic steroid therapies as initial therapy for idiopathic sudden sensorineural hearing loss: a meta-analysis. Acta Otolaryngol 2017;137:598-605. [Crossref] [PubMed]
14. Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical practice guideline: sudden hearing loss. Otolaryngol Head Neck Surg 2012;146:S1-35. [Crossref] [PubMed]
15. Dispenza F, Amodio E, De Stefano A, et al. Treatment of sudden sensorineural hearing loss with transtympanic injection of steroids as single therapy: a randomized clinical study. Eur Arch Otorhinolaryngol 2011;268:1273-8. [Crossref] [PubMed]
16. Zhou Y, Zheng H, Zhang Q, et al. Early transtympanic steroid injection in patients with ‘poor prognosis’ idiopathic sensorineural sudden hearing loss. ORL J Otorhinolaryngol Relat Spec 2011;73:31-7. [Crossref] [PubMed]
17. Clinical Practice Guideline: Sudden Hearing Loss (Update). American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS). Available online: https://www.entnet.org/quality-practice/quality-products/clinical-practice-guidelines/sudden-hearing-loss-update/
18. Tinnitus Handicap Inventory (THI). Available online: https://ata.org/wp-content/uploads/2022/08/Tinnitus_Handicap_Inventory.pdf
19. Definition and diagnosis of diabetes mellitus and intermediate hyperglycemia RepoRt of a WHo/IDf ConsultatIon. Available online: https://iris.who.int/bitstream/handle/10665/43588/9241594934_eng.pdf
20. World Health Organization. Hypertension. Who.int. World Health Organization: WHO; 2023. Available online: https://www.who.int/news-room/fact-sheets/detail/hypertension?utm_source=chatgpt.com
21. Moon IS, Lee JD, Kim J, et al. Intratympanic dexamethasone is an effective method as a salvage treatment in refractory sudden hearing loss. Otol Neurotol 2011;32:1432-6. [Crossref] [PubMed]
22. Teles S, Freitas L, Bernardo G, et al. Tinnitus evolution in patients with sudden sensorineural hearing loss treated with hyperbaric oxygen therapy. Revista Portuguesa de Otorrinolaringologia-Cirurgia de Cabeça e Pescoço 2023;61:7-15.
23. Ding X, Zhang X, Huang Z, et al. The Characteristic and Short-Term Prognosis of Tinnitus Associated with Sudden Sensorineural Hearing Loss. Neural Plast 2018;2018:6059697. [Crossref] [PubMed]
24. Radhakrishnan K, Kumar DR, Balasubramani J, et al. Efficacy of Intratympanic Dexamethasone Injection in Subjective Idiopathic Tinnitus-An Interventional Study. Journal of Clinical & Diagnostic Research 2022;16:MC05-8.
25. Joshua TG, Ayub A, Wijesinghe P, et al. Hyperbaric Oxygen Therapy for Patients With Sudden Sensorineural Hearing Loss: A Systematic Review and Meta-analysis. JAMA Otolaryngol Head Neck Surg 2022;148:5-11. [Crossref] [PubMed]
26. Mayo Clinic. Meniere’s disease - Diagnosis and treatment - Mayo Clinic. 2018. Available online: https://www.mayoclinic.org/diseases-conditions/menieres-disease/diagnosis-treatment/drc-20374916
27. Včeva A, Zubčić Ž, Mihalj H, et al. Pretreatment hearing grades and hearing recovery outcomes after primary hyperbaric oxygen treatment in patients with idiopathic sudden sensorineural hearing loss. Diving Hyperb Med 2022;52:191-6. [Crossref] [PubMed]
28. Cheng YF, Chu YC, Tu TY, et al. Modified Siegel’s criteria for sudden sensorineural hearing loss: Reporting recovery outcomes with matched pretreatment hearing grades. J Chin Med Assoc 2018;81:1008-12. [Crossref] [PubMed]
29. Park CH, Lee YJ, Kim MK, et al. Clinical characteristics and prognosis of idiopathic sudden sensorineural hearing loss in old age. Korean J Otorhinolaryngol-Head Neck Surg 2014;57:511-7.