Kosyakov 2011.

Study characteristics
Methods	Non‐blinded, parallel‐group randomised controlled trial with 6‐month duration of treatment and 6‐month duration of follow‐up
Participants	Setting: tertiary referral centre, Russia, no dates provided Sample size: Number randomised: 73 Number completed: 73 Primary/secondary therapy: primary therapy Participant (baseline) characteristics: age/sex (male, female)/hearing loss at start of therapy/start of treatment: Group I (intratympanic): 49 (35 to 52) y/14 m, 10 f/41.0 ± 12.87 dB HL/not reported Group II (systemic): 50 (30 to 53) y/15 m, 9 f/37.1 ± 16.67 dB HL/not reported Group III (systemic): 40 (32 to 53) y/13 m, 12 f/39.1 ± 16.97 dB HL/not reported Inclusion criteria: SSNHL with hearing loss in 3 contiguous frequencies of at least 30 dB, who had not previously been treated and were at least 18 years old; treatment delay less than 1 monthExclusion criteria: 1) patients with somatic pathology (such as diabetes, hypertension, gastric ulcer, tuberculosis, glaucoma, etc.), for whom systemic steroids were contra‐indicated; 2) oncology patients; 3) patients with autoimmune diseases or those who were constantly or periodically taking steroids; 4) patients who were or have been taking ototoxic agents; 5) patients with acoustic neurinoma; 6) pregnant and nursing women; 7) patients with middle ear diseases, abnormal type of tympanometric curves or barotrauma in their anamnesis; 8) those who had intolerance for any component of treatment; 9) those who had SSNHL in the only hearing ear
Interventions	General comparison: intratympanic versus systemic corticosteroid therapy Intervention group I (n = 24*): "intratympanic therapy": intratympanic injection of dexamethasone, 4 mg/mL (volume not specified), every day for 10 days, then every other day over 20 days, then 2 times a week over further 5 months Comparator group I (n = 24*): "systemic therapy": intravenous dexamethasone 0.1 mg/kg daily for 10 days, followed by a decreasing dose over 5 days Comparator group II (n = 25*): "systemic therapy": intravenous dexamethasone 0.1 mg/kg daily for 10 days, followed by a decreasing dose over 5 days Use of additional interventions (only used in comparator group I): pentoxifylline, cocarboxylase, potassium and magnesium aspartate intravenously and vitamin B‐complex intramuscularly *intention‐to‐treat analysis
Outcomes	Primary outcome measure: Proportion of patients whose hearing is improved (criterion of improvement > 15 dB decrease in PTA) Secondary outcomes: Proportion with hearing improvement (> 15 dB in PTA) with partial recovery (minimum 50% PTA improvement from baseline) and with complete recovery (to within 15 dB difference in PTA of the unaffected ear) Mean improvement of PTA and in frequency‐specific bands Recovery over time (1 and 6 months) Primary endpoint for hearing threshold evaluation: 183 days Used PTA: 4PTA (0.5, 1, 2, 4 kHz)
Funding sources	No information available
Declarations of interest	No information provided
Notes	Intratympanic treatment was administered over 6 months, which is much longer than all other intratympanic treatment protocols in this review. Also, the duration of intratympanic and systemic therapy differed considerably, intratympanic therapy lasting 6 months and systemic therapy lasting only 15 days. We therefore investigated whether the inclusion of this study had a notable impact on the overall results by conducting a sensitivity analysis in which it was excluded.  Only the group receiving systemic corticosteroid without additional treatment was included as a comparator. This was because the additional treatments were not received by the group receiving intratympanic corticosteroid. This study was included in meta‐analyses despite a unit of analysis of ears instead of patients, as only 2 patients with bilateral hearing loss were included.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote from protocol: "The randomisation will be done using a random number table of the software Statistica (StatSoft Inc., version 6.1)."
Allocation concealment (selection bias)	Unclear risk	Method of concealment is not described.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Open‐label trial, no blinding.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote from protocol: "Audiologists producing hearing loss assessment will be blinded".
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing outcome data reported.
Selective reporting (reporting bias)	Low risk	Primary and secondary outcome criteria are pre‐specified in the later sent protocol and reported in the results of the publication.
Other bias	High risk	No sample size calculation performed. Treatment delay from onset in patients not reported. Only mild cases of ISSNHL included. Wide range of treatment delay from onset in inclusion criteria. Some participants (n = 2) had bilateral disease, but analysis does not account for correlation between ears. Duration of treatment longer in intervention arm (6 months) than in the comparator arm (15 days).