RecruitingProcedureExternal Lumbar Drainage to Reduce ICP in Severe TBI: a Phase 1 Clinical TrialThe goal of this phase 1 randomized controlled safety and feasibility clinical trial are to determine the safety of external lumbar drainage (ELD) in select patients with severe Traumatic Brain Injury (TBI). The main questions it aims to answer are (i) if ELD is feasible and (ii) safe to perform in severe TBI patients who have radiological evidence of patent basal cisterns and midline shift \<5mm without increasing the risk of neurological worsening or cerebral herniation. All participants will receive routine usual care. The study group will additionally have ELD for cerebrospinal fluid (CSF) drainage. A comparison will be made between the usual treatment plus ELD (interventional) groups, and the usual treatment (control) groups on incidence rate of neurological worsening or cerebral herniation events, and whether total hours with raised intracranial pressure (ICP) are different.