Statistical analysis plan for the Dex-CSDH trial: a randomised, double blind, placebo-controlled trial of a two-week course of dexamethasone for adult patients with a symptomatic Chronic Subdural Haematoma

Background: The incidence of chronic subdural haematoma (CSDH) is increasing. Although surgery remains the mainstay of management for symptomatic patients, uncertainty remains regarding the role of steroids. Hence, the Dex-CSDH trial was launched in the UK in 2015 aiming to determine whether, compared to placebo, dexamethasone can improve the six month functional outcome of patients with symptomatic CSDH by reducing the rate of surgical intervention and recurrence rate. Methods and design: Dex-CSDH is a multi-centre, pragmatic, parallel group, double-blind, randomised trial assessing the clinical utility of a two-week course of dexamethasone following a CSDH. 750 patients were randomised to either dexamethasone or placebo. The primary outcome is the modi ed Rankin Scale at six months which is dichotomised to favourable (score of 0-3) versus unfavourable (score of 4-6). Conclusions: This paper and the accompanying additional material describes the statistical analysis plan for the trial.