In Chapter 2, the study protocol is described of the BRAIN-PROTECT study, the first Dutch prospective observational study on prehospital epidemiology and treatment of patients with severe traumatic brain injury (TBI). The main objective of this research project was to identify prehospital factors, in particular treatment strategies, associated with beneficial or detrimental outcomes in patients with suspected severe TBI. The BRAIN-PROTECT study inclusion started in 2012 and prehospital inclusion continued until December 2017 (Follow-up until December 2018). In total, 2,589 patients were included (Chapter 3The incidence rate of suspected severe TBI was 3.2 (per 100,000 inhabitants per year) and 2.7 for confirmed TBI. Age ranged between 1 and 97 years and 70.8% were male. The overall 30-day mortality was 39.0% for the overall population of severe TBI and for confirmed TBI 42.4%. In Chapter 5, the results of a retrospective study on neurological deterioration are presented. 13% of 808 patients with initial mild TBI showed a discrepancy between the initial assessment of TBI severity based on the GCS, and the actual TBI severity as determined post hoc. In Chapter 6 face-to-face and telephonic examination of the GOS-E - an extended score on neurological functioning after neurotrauma - were compared. These showed a kappa value of 0.79, which is commonly considered good or substantial agreement, and implies that telephonic assessment is a valid alternative. Most of the prehospital treatments for severe TBI lack a thorough base of evidence. Prehospital airway management is regularly performed, but it’s benefit is not yet fully established. In Chapter 7, a systematic review and meta-analysis was performed to address effects of Prehospital Intubation (PHI) on mortality in patients with severe TBI. Six studies met the inclusion criteria for the meta-analysis. The main finding is that effects of PHI depend on the level of experience of the Emergency Medical Service (EMS)-providers who perform the intervention, and that PHI ...