Not Too Late for Steroids: A Look at the Effects of Delayed Onset Steroid Treatment in Sudden Sensorineural Hearing Loss

INTRODUCTION

Sudden sensorineural hearing loss (SSNHL) is commonly defined as hearing loss greater than 30 dB and involving at least three consecutive audiometric frequencies, occurring within 3 days without any identifiable cause.^1,2 In the United States, 4,000 new cases of SSNHL occur annually. The incidence ranges from 11 per 100,000 for patients less than 18 years old to 77 per 100,000 for patients older than 65.³ There is also a slight male preponderance with a male-to-female ratio of 1.07:1, which is more pronounced in patients over age 65.³ The etiology of SSNHL remains unclear and may be multifactorial. Vascular compromise, viral infection, and immune-mediated reactions have been postulated to cause SSNHL.^1,4

Various treatments have been proposed for SSNHL, such as steroids consisting of oral, intravenous, and intratympanic (IT) steroid injections, vasodilators, and hyperbaric oxygen therapy. However, oral and IT steroid injections are considered the mainstay of therapy. IT steroid therapy can provide targeted treatment with the application of high doses of the drug directly in the middle ear over the round window membrane, thereby avoiding the adverse systemic effects of corticosteroid therapy.⁵

Controversy still exists over the specific time frames in which patients with SSNHL can achieve hearing benefits. Studies show that starting steroid treatments early, preferably within 72 hours of symptom onset, provides the greatest long-term hearing benefits. The efficacy of IT steroid therapy has been demonstrated in several prospective, randomized, placebo-controlled trials.^6,7 Current guidelines recommend oral steroids within 2 weeks of onset and IT injections within 2–6 weeks of onset.⁸ The American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines for SSNHL also recommend that clinicians should offer IT steroid injections when patients have incomplete recovery from SSNHL after failure of initial oral steroid management.⁸ The rate of spontaneous recovery without steroid treatment can range from 32% to 65%, while the rate of full recovery within the recommended guidelines in treated patients can range from 49% to 79%.⁹ SSNHL can additionally present with different individual audiometric curves, each showing a different course of disease and response to therapy.¹⁰

The impact of the time to initiation of treatment on hearing prognosis has not yet been established.¹¹ As a majority of our patients with SSNHL present to us outside the recommended treatment time frame, sometimes up to 1 year after onset of hearing loss, the purpose of this study is to determine how delayed timing of steroid treatment, specifically oral and IT steroid injections, can affect overall hearing. In the present study, we performed a retrospective case review of 20 patients who received oral and/or IT steroid therapy outside the recommended guideline period for initial treatment and examined what benefits in hearing may still be achieved for these patients.

MATERIAL AND METHODS

The medical charts of 20 patients diagnosed with SSNHL presenting to the Louisiana Shreveport outpatient otolaryngology clinic from January 2016 to January 2020 were retrospectively reviewed. The Louisiana State University Health Sciences Center Shreveport (LSUS) Institutional Review Board approved the study. Inclusion criteria consisted of patients of all ages, genders, and ethnicities with a diagnosis of SSNHL within the past 4 years; patients presenting either immediately after hearing loss or anywhere up to 12 months after the onset of hearing loss; and patients who received either oral steroids or IT injections or both as initial therapy for SSNHL outside of the recommended guidelines, up to 1 year after initial diagnosis. Exclusion criteria consisted of patients who were already treated with antivirals, patients who had a prior history of Meniere’s disease confirmed with electrocochleography (ECOG) and videonystagmography (VNG) testing, or patients with cerebellopontine angle tumors. Other exclusion criteria consisted of patients who received IT injections but were lost to follow-up and did not receive a post-treatment audiogram.

IT steroids were injected in our patients as follows: The tympanic membrane was anesthetized with 4% lidocaine. A 25-gauge 3.5-inch spinal needle was used to inject. 3 ml of 10 mg/ml dexamethasone into the middle ear space via the posterior inferior quadrant.

Patient characteristics for this study are outlined in Table 1.

Patients who received oral steroids 2 weeks or more after the onset of SSNHL were surveyed for any perceived improvement in hearing level. We also examined patients given IT steroid injections outside the recommended treatment timeframe, anywhere from 6 weeks up to 1 year after SSNHL onset. Patients who received IT steroid injections either had a failure with a prior course of oral steroids or no prior oral steroid therapy. Perceived hearing improvement by the patient was recorded in these patients at clinic visit follow-up appointments after treatment.

Patients given IT steroid injections were further evaluated during pretreatment and at 1-week post-treatment. Standardized methods for pure tone threshold audiometry with Pure Tone Average (PTA) were calculated as the mean of thresholds at 250, 500, 1,000, 2,000, 4,000, and 8,000 Hz. Based on the PTA scores, patients were classified into four audiometric curve groups: up-sloping (low frequencies affected), down-sloping (high frequencies affected), flat moderate to severe (all frequencies involved with PTA between 40 and 90 dB), and profound (flat audiogram with PTA more than 90 dB). Speech recognition threshold (SRT) improvement and word recognition score (WRS) improvement were also examined in each of these patients, both pre- and post-treatment.

Various classifications have been suggested for the hearing recovery reporting systems. Siegel’s criteria for improvement show final hearing outcomes and absolute hearing gains.¹² According to Siegel’s criteria for hearing improvement, “good recovery” was defined as more than 15 dB gain and final hearing better than 45 dB, and “poor recovery” was defined as less than 15 dB gain and final hearing poorer than 45 dB.¹² Furuhashi further broke down hearing improvement as complete recovery, marked improvement, slight improvement, or no recovery based on changes in PTA. Complete recovery consisted of a six-frequency pure-tone average consistently ≤25 dB or identical to the contralateral, non-affected ear. The marked improvement consisted of any PTA frequency >30 dB. Slight improvement consisted of any PTA frequency between 10 and 30 dB. No recovery was considered for any PTA frequency <10 dB.¹³ The evaluation of hearing improvement in our patients was performed using a combination modeled after Siegel and Furuhashi criteria [Table 2]. Patients in this study were graded as complete improvement, marked improvement, poor improvement, or no improvement. Complete improvement was defined as PTA across six frequencies (250, 500, 1,000, 2,000, 4,000, and 8,000 Hz) showing ≤25 dB or identical to the contralateral, non-affected ear. Marked improvement was defined as PTA improvement >30 dB or SRT improvement of 15 dB or more. Poor improvement was defined as PTA improvement <30 dB but ≥10 dB or SRT improvement of less than 15 dB, and no improvement was defined as PTA showing <10 dB or no improvement in SRT. Marked or complete improvement was defined as successful treatments. WRSs were considered improved if there was any change greater than 10%.

RESULTS

Sixty-two percent of our patients reported noticeable clinical improvement in hearing after delayed IT injections. This was seen primarily with patients who were treated with IT injections within 5 months of hearing loss onset. Patients treated between 6 and 12 months from onset did not perceive much benefit. All patients’ PTAs and WRSs were compared pre- and post-steroid treatment. Pre-treatment scatter plots of pure tone thresholds and WRSs for each patient in our study are shown in Figure 1a. Post-steroid treatment scatter plots of PTA and WRS are shown in Figure 1b. When looking at post-treatment scores, 47% of patients had no change in PTA, whereas 41% did show an increase in PTA score. For word recognition, 41% of patients improved, with an overall average score increase of 22%. WRS improvement was seen at all months out from hearing loss onset, independent of time from onset to steroid treatment. 35% of patients improved in WRS at 5 months or less from hearing loss onset; however, improvement was seen up to 1 year out from onset in 5% of these patients [Figure 2].

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Figure 1:

Pre and post-treatment scatter plots of PTA and WRS in each patient. (a) scatter plot of patients’ PTA and WRS pre-steroid treatment (n = 17). (b) scatter plot of patients’ PTA and WRS post steroid treatment (n = 17). PTA: Pure tone audiogram, WRS: Word recognition score.

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Figure 2:

WRS improvement. The x-axis shows months from SSNHL onset to steroid treatment (IT steroid injection). The y-axis shows a WRS increase in % per patient. WRS: Word recognition score, IT: Intra-tympanic steroid, SSNHL: Sudden sensorineural hearing loss.

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When looking at the mean increase in SRT scores to examine hearing improvement in each patient after IT injections, we found that patients who had IT injections between 6 weeks and 5 months after SSNHL onset showed higher increases in SRT scores than those patients injected after 5 months from onset. Figure 3 separates patients who had steroid injections at ≤5 months from SSNHL onset and at >5 months from onset and highlights the increases in SRT scores. Patients who had injections at ≤5 months from SSNHL onset showed a greater improvement in hearing based on a higher increase in SRT score (mean 22.5 dB) compared to those with injections after 5 months of SSNHL onset (mean of 2.5 dB; p = 0.08). The maximum increase in SRT was 45 dB for patients injected within <5 months from onset. The patient group that was injected >5 months from hearing loss onset showed the greatest SRT value at 6 months; this maximum increase score was 10 dB.

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Figure 3:

Mean SRT increase per patient vs. months delay in IT steroid injection. The x-axis shows patients who had IT steroid injections at ≤5 months (6 weeks to 5 months) from SSNHL onset and at >5 months (6 months to 1 year) from onset. The mean increase in the SRT score is shown on the y-axis. Patients with injections <5 months from onset show a higher increase in SRT score (mean 22.5 dB, standard deviation = 12.2) compared to those with injections after 5 months (mean of 2.5 dB, standard deviation = 7.07; p = 0.08). IT: Intra-tympanic, SSNHL: Sudden sensorineural hearing loss, SRT: Speech reception threshold.

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Patients’ hearing improvement after steroid injection was also compared for different audiometric curves [Figure 4]. Patients’ audiometric curves were classified into the following patterns: up-sloping (low-frequency hearing affected), down-sloping (high-frequency hearing affected), flat (all frequencies involved with PTA between 40 and 90 dB), and profound (flat audiogram with PTA more than 90 dB). Hearing improvement scales consisted of complete improvement, marked improvement, poor improvement, and no improvement. None of our patients showed a complete improvement. All the patients who had down-sloping audiograms showed no improvement after IT injection, independent of how long the delay was. Out of the patients who had upsloping and flat audiograms, these patients had either no improvement, poor improvement, or marked improvement. 60% of patients with flat audiogram curves displayed no improvement, while 20% displayed poor and marked improvement. 50% of patients with upsloping audiogram curves displayed marked improvement, with 25% showing poor or no improvement. In the profound category, there was only one patient who displayed poor improvement (10 dB PTA increase at both 1,000 and 2,000 Hz with no subjective improvement noted from the patient-on-patient survey).

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Figure 4:

Improvement in hearing and audiometric curve after steroid treatment within different audiometric curve patterns.

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DISCUSSION

As many of our patients are referred to us well after the onset of SSNHL, there is a need to understand how to manage these patients. The patients may or may not have been evaluated by outside physicians and experience long waiting times to get an appointment to see an otologist or otolaryngologist, or they do not always self-report the sudden hearing loss during immediate onset. It is important to be aware of the benefits of hearing improvement that may occur with delayed initiation of steroid treatment in these patients.

SSNHL in children is considered rare.¹⁵ Studies show that children treated within 14 days of onset have a much better prognosis than those treated over 14 days from onset with IT steroid injections.^16,17 This finding indicates that 14 days may be a valuable time frame for the treatment of SSNHL; however, improvements have also been reported in children with a longer history of even more than 6 months.¹⁶

Studies have also found that the recovery rate is associated with patient age, i.e., younger patients have better outcomes in hearing recovery.¹⁸ In some studies, it is known that vertigo is a negative factor, while younger age, unilateral hearing loss, and early treatment are positive prognostic factors of hearing recovery.^17,19–21

Sixty-two percent of our patients reported noticeable clinical improvement in hearing after delayed IT injections. This was observed primarily in patients treated with IT injections within 5 months of hearing loss onset. Patients treated between 6 and 12 months after the onset of hearing loss did not perceive any significant benefit.

The limitations of our study include the small size of the cohort, the retrospective nature of the study, the possibility for bias in data collection and analysis, and the challenges related to causality and data quality.

Future trends include increasing the cohort size and following patients for a longer duration to observe temporal trends as well as the association of comorbid factors influencing outcomes.

CONCLUSION

From our review, patients treated outside the recommended guideline window not only show subjective benefits on the survey but also show increases in PTA, SRT, and WRS. This benefit is seen primarily in patients who are treated with IT steroid injections within 5 months or less from SSNHL onset.