A retrospective cross-sectional study was conducted in Otorhinolaryngology Department of a tertiary teaching hospital. Data collection duration was from first January 2019 to 31^st December 2020. Analysis done from first April 2021 to 30^th June 2021. Records of all patients with diagnosis of sudden SNHL in 2019 and 2020 were analysed after obtaining Ethical Clearance from Institutional Ethical Committee and Research Committee. (HIMS/RC/2021/48).

Inclusion criteria: All patients presenting with history of sudden hearing loss of sensorineural nature within 72 hours, who had minimum 30 dB hearing loss in three contiguous frequencies among 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz, were included in present study.

Exclusion criteria: All patients with mixed or conductive hearing loss were excluded from study. Patients with history of head trauma, chemotherapy, radiotherapy, diabetes mellitus or known autoimmune diseases and those who were diagnosed with Meniere’s disease or retrocochlear hearing loss during the course of treatment were also excluded.

All of these patients underwent thorough Ear, Nose and Throat (ENT) examination including otoscopy, zero degree otoendoscopy and tuning fork tests. Total 27 patients were finally enrolled in this study. Out of 27 patients 8 patients were having bilateral sudden SNHL. So, total 35 case ears were analysed in present study, considering each ear as a separate case. All cases were divided in to three groups for statistical analysis.

Audiometric assessment was done by qualified audiologist with masters degree using inter acoustic AD 629 audiometer after proper daily calibration. All patients underwent pure tone audiometry assessment before the start of treatment, after 3^rd transtympanic injection and seven days after the discharge from hospital during follow-up visit. Pretreatment audiogram and seven days post-treatment follow-up audiogram were analysed for assessing gain in hearing threshold.

Transtympanic steroid injections were given by ENT surgeon with minimum five years work experience after obtaining masters degree. Total three transtympanic injections were given on day one, day three and day five using 25 gauze needle in posteroinferior quadrant of tympanic membrane. Local anaesthesia was given using 10% lidocaine soaked cotton ball over tympanic membrane for about 15 minutes. Total 0.5 mL methyl prednisolone with consistency of 40 mg/mL was instilled every time. In bilateral cases 30 minutes gap was kept between injection on either side. Patient was asked not to swallow and lie down on opposite side for 20 minutes. All patients vitals were monitored for 30 minutes after the injections.

All data collected using case recording pro forma was entered in MS excel 2010. Data analysis was performed using Statistical Package for the Social Sciences (SPSS) software version 20.0. Data was analysed using student paired t-test independent t-test and one-way Analysis of Variance (ANOVA) test. If p-value <0.05, then data was considered significant.

In present study, out of 27 patients, 19 (70%) were male while 8 (30%) were female in age range of 18-56 years with median age of 40 years. Out of these 27 patients, 10 (37%) patients had right side sudden, 9 (33.3%) patients had left side sudden SNHL. Total 8 (29.6%) patients (four male and four female) had bilateral sudden SNHL. So, there were total 35 case ears with the diagnosis of sudden SNHL. Patients presented to hospital from day one of onset of symptoms to sixty days of onset of symptoms with median presentation being day six of hearing loss. Total 11 (31.4%) number of case ears received treatment within four days of their onset of symptoms, 11 (31.4%) number of case ears from four days to within seven days while 13 (37.2%) number of case ears received treatment after seven days [Table/Fig-1].

Out of 35 case ears of 27 patients, 18 (51.4%) were less than 40 years of age while 17 (48.6%) were more than 40 years of age. Out of 35 case ears 16 (45.7) were bilateral (eight patients with bilateral SNHL) while 19 (54.3%) were unilateral case ears. Post-treatment average gain for frequency 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz were 18 dB, 25 dB, 27 dB, 28 dB and 30 dB, respectively [Table/Fig-2].

On statistical analysis p-value was less than 0.05, so this suggests significant improvement in all frequencies [Table/Fig-3].

Among the group 1 case ears average hearing gain was 48.5%, among group 2 average hearing gain was 39.2% while among group 3 it was 39.3% average hearing gain. Average hearing gain among less than 40 years case ears was 44.3% while among more than 40 years case ears it was 41.8%. Average hearing gain among bilateral case ears was 42.9% and among unilateral case ears it was 43.5%.

Although, significant hearing gain was seen in patient who received treatment within four days compare to delayed treatment but it was statistically not significant. There was no statistically significant difference between less than 40 years and more than 40 years. There was no statistically significant difference in unilateral and bilateral cases [Table/Fig-4].

Sudden SNHL is a terrifying and crippling event which may impair social life if a person do not recovers from it. Idiopathic sudden SNHL is a diagnosis of exclusion. Common probabilities are viral infections, vessel occlusion, breaks in membrane and immunology related [2]. Due to variable aetiologies different treatment options are in practice. These treatment options like antiviral, steroids, heparin, carbon and hyperbaric oxygen therapy are used alone or in combination [7]. In the present study there were 70% male and 30% female patients. Authors saw clear male preponderance but literature suggest only slight in proportion of 1.30:1 in patient more than 60 years [10]. A study from South Korea reported female preponderance in preparation of 1.35:1 for sudden SNHL [11]. Authors had 40 years as median age of sudden SNHL patients. Anyah A et al., reported 54 years as average age for sudden SNHL in their study [12]. In the present study, 37% patients had right sided sudden SNHL, 33.3% had left sided and 29.6% had bilateral sudden SNHL. So, in the present study 70.3% patients had unilateral sudden SNHL and 29.6% patients had bilateral sudden SNHL. Sara SA et al., reported total 103 cases of bilateral sudden SNHL in their review [13]. In the present study, median presentation was six day from symptoms ranging from 1-60 days. In study by Anyah A et al., average presentation was 55^th day ranging from 1-240 days of onset of symptoms [12]. In the present study, 31.4% cases received treatment within four days and 37.2% cases after seven days. Patients who received treatment within four days had average 48.5% hearing gain while those who received between four to seven days and those who received after seven days had average 39.2% hearing gain. So, it suggests less time interval between onset of symptom and start of treatment in sudden SNHL is important. So, it clarifies diagnosis of sudden SNHL within 72 hours and urgent treatment is golden point. In present study, we found hearing gain in all patient who received transtympanic steroid injection. However, patients receiving within four days of onset of symptoms compare to those who received after four days had average 9.3% more hearing gain. It also suggests that results after four days or after seven days have no significant difference. However, results among these three groups were not statistically significant which may be due to smaller number of sample size warranting larger study on sudden SNHL. Gupta V et al., reported complete recovery in 52.38% cases of sudden SNHL who presented within 72 hours and only complete recovery in 12.5% cases who reported after 72 hours [14]. Possible reasons for poor prognosis in cases of delayed treatment may be irreparable inflammatory damage to vascular stria which is the site of insult in sudden SNHL [15]. In present study, there was no significant difference in average hearing gain among cases less than 40 years and more than 40 years. Bhandari A and Jain S also reported no significant difference in hearing gain in cases less than and more than 50 years [16]. In the present study, author did not find any significant difference in average hearing gain between unilateral and bilateral cases. In present study, frequency specific hearing gain was also assessed. We found average hearing gain of 46.2%, 44.6%, 40.9%, 38.8% and 37.9% in frequencies of 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz, respectively. This suggests that maximum hearing gain was seen in lower frequencies. It also suggests that average hearing gain decreases with upper frequencies. Bhandari A and Jain S also reported greater improvement in lower frequencies [16].

Now a days steroids either systemic or transtympanic or in combination are most widely accepted treatment in sudden SNHL. Transtympanic steroid injection can also be given in patients who otherwise contraindicated for systematic steroids. Possible mechanism for transtympanic steroid administration is diffusion. Steroid diffuses from round window in to cochlear turn in base to apex direction [17]. New research options for sudden SNHL are mesenchymal stem cell therapy which may act by inner ear regeneration [18]. Tumour Necrosis Factor Alpha (TNFα) targeted therapies have shown some promising results in animal models for sensorineural hearing loss [19].

First limitation of present study was sample size due to less incidence and delayed reporting of patient to tertiary care otology centre. Second limitation of present study was design of study as this was a retrospective study. Better study may be double blinded multicentre prospective cohort study having two groups one receiving transtympanic steroids injections while other receiving placebo or no transtympanic steroid injection. But there may be ethical issues in conducting such study.

Sudden SNHL is an otological emergency, so it should be diagnosed and treated promptly. Transtympanic steroid injections are most favoured cost effective treatment option due to feasibility, acceptability and less side effects in skilled hands. Patients who present early have significant improvement in average hearing thresholds. There is better improvement in lower frequencies and there is no significant effect of patient’s age and laterality of sudden SNHL. Further research and large meta-analysis is need of hour to prove significant efficacy of transtympanic steroid injection in sudden SNHL.