Inclusion and exclusion criteria
Two authors (J.H.S. and D.H.L.) independently selected studies for analysis according to the following inclusion criteria: (a) type of participants: patients with VN; (b) type of intervention(s): corticosteroid treatment, combination of corticosteroids plus other treatments (vestibular exercise, valacyclovir et al.); (c) type of comparative treatment: Placebo, no treatment, other treatments (vestibular exercise, valacyclovir et al.) (d) outcome measure(s): Complete caloric recovery (defined as canal paresis in caloric testing return within 20-25%), improvement (as %) of canal paresis (CP) in caloric testing, dizziness handicap inventory (DHI); and (e) type of study: Randomized controlled trials (RCTs). Studies were excluded in the following situations: (a) the study had no original data and/or was an editorial article or conference abstract;(b) there were no proper outcomes data; (c) the article was not written in English; (d) the article was a non-randomized controlled trial, cohort study, case-control study, animal experiment, chemistry, or cell-line study or editorial, commentary, review article, or case report. Two independent authors (J.H.S. and D.H.L.) screened the studies. The studies were identified by title, abstract, and text in the first screening. The full texts of the relevant studies were retrieved for validation before final acceptance in the present systematic review. The search strategy was based on the PRISMA reporting guideline and a flowchart of the study selection process is shown in Figure 1.