Table 5. Hearing recovery according to the starting treatment from onset

Author (years)	Patient number treatment	Recovery criteria	Duration from onset to treatment: hearing recovery (%)
Byl (1984)1)	• n=225• Steroid alone	• Normal return: ≤25 dB• Complete return : <10 dB of opposite ear	• 0–7 d: 56% (Normal & complete)• ≥30 d: 27% (Normal & complete)
Zadeh et al. (2003)8)	• n=51• Steroid alone	• Recovery: return of half the difference, between the affected and unaffected ear	• 0–3 d: 75%• 4–7 d: 67%
Nosrati-Zarenoe et al. (2007)9)	• n=208• Steroid alone	• Large improvement (LI) : >30 dB of gain	• 0 d: 30%, 72%, 30%• 7 d: 23%, 58%, 20%• 30 d: 23%, 17%, 4%LI rates for low, mid, and high frequency, respectively.
Čvorović et al. (2008)7)	• n=541 ≤7 d (451) >7 d (90)• Steroid alone	• Significant recovery: ≤30 dB	• ≤24 h: 56%• ≤7 d: 60%• >7 d: 40%
Lee et al. (2014)10)	• n=289 ≤7 d (242) >7 d (47)• Steroid alone	• CR: ≤25 dB• PR: gain (≥15 dB) and 25–45 dB• SR: gain (≥15 dB) and >45 dB	• ≤3 d: 73.8% (CR+PR+SR)• 4–7 d: 82.7%• >7 d: <30%
Bulğurcu et al. (2018)11)	• n=1540–3 d (61)4–7 d (60)8–15 d (24)15–30 d (9)• Combination steroid	• CR: ≤25 dB• PR: 10–42 dB of gain• NR: <10 dB of gain	• 0–3 d: 13% (CR), 18% (PR)• 4–7 d: 16% (CR), 18% (PR)• 8–15 d: 2% (CR), 7% (PR)• 15–30 d: 0% (CR), 2% (PR)
Xie et al. (2019)12)	• n=129• Steroid alone	• Improved hearing: ≥15 dB of gain or <26 dB	• ≤10 d: 31/46 (67.3%)• <21 d: 4/13 (30.7%)• <30 d: 1/4 (25.0%)• 30 d: 19/35 (54.2%)

d: days, h: hours, diff: difference, LI: large improvement, CR: complete recovery, PR: partial recovery, SR: slight recovery.