Hong 2009.

Study characteristics
Methods	Non‐blinded, parallel‐group randomised controlled trial with 8 days duration of treatment and 3‐month duration of follow‐up
Participants	Setting: tertiary referral centre, Republic of Korea, May 2007 to January 2009 Sample size: Number randomised: 75 Number completed: 63 Primary/secondary therapy: primary therapy Participant (baseline) characteristics: age/sex (male, female)/baseline hearing loss at start of therapy/start of treatment: Group I (intratympanic): 56.9 y/13 m, 19 f/77.5 ± 27.6 dB HL/3.4 d Group II (systemic): 56.2 y/11 m, 20 f/79.9 ± 23.5 dB HL/3.9 d Inclusion criteria: ISSNHL of 30 dB or more with over 3 contiguous audiometric frequencies that occurred in fewer than 3 days Exclusion criteria: ISSNHL with vertigo, diabetes, Ménière’s disease, tumours, treatment onset of more than 15 days
Interventions	General comparison: intratympanic versus systemic corticosteroid therapy Intervention group (n = 32*): "intratympanic therapy": intratympanic injection of dexamethasone, 5 mg/mL, 0.3 to 0.4 mL, 8 injections total, 1 x per day Comparator group (n = 31*): "systemic therapy": oral prednisolone 60 mg per day for 4 days, 40 mg per day for 2 days and 20 mg per day for 2 days Use of additional interventions (only comparator group):"peripheral vasodilator" and Ginkgo biloba extract *per protocol analysis
Outcomes	Primary outcome measure: Change in hearing threshold with pure tone audiometry Secondary outcomes: Frequency‐specific changes with pure tone audiometry Proportion of patients whose hearing is improved (criterion of improvement > 15 dB decrease in PTA/Siegel's criteria) Adverse events Primary endpoint for hearing threshold evaluation: 90 days Used PTA: 4PTA (0.5, 1, 2, 3 kHz)
Funding sources	Grant (code # 200810FTH010103002) from BioGreen21 Program, Rural Development Administration, Republic of Korea
Declarations of interest	None declared
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "IT dexamethasone or oral prednisolone, was assigned for patients with ISSHL alternatively and randomly." Method of random sequence generation is not described.
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: "outcome assessors were blinded"
Incomplete outcome data (attrition bias) All outcomes	High risk	Rate of reported missing outcome data more than 10% (16%).
Selective reporting (reporting bias)	Low risk	No indication of selective reporting in the outcome parameters addressed by the review.
Other bias	High risk	No sample size calculation performed. Standard deviation of treatment delay from onset not reported.