Analysis: Our sample size consideration is based on the second prognostic question to predict the outcome of neurological and neurosurgical patients. To determine an optimal clinical model we will undertake a multivariable regression analysis to assess which variables are independently associated with outcome. Multiple regression models with a minimum of 10 to 15 observations per predictor variable reveal good estimates. We will evaluate 18 predictors in our multivariate analysis. Therefore, we aim to include a minimum sample size of 180 patients (for 10 observations per predictor) to 270 (for 15 observations per predictor) and a maximum sample size of 360 patients (for 20 observations per predictor).