Autoregulation after traumatic brain injury can be monitored continuously using simple signal processing of intracranial pressure and arterial blood pressure. The pressure reactivity index (PRx) showed several benefits when it was applied to continuous brain monitoring. Among them, a positive and strong correlation with the outcome and possibility of calculation of 'optimal cerebral perfusion pressure' have been listed. For this methodology, prospective clinical trials are missing-few of them are planned in the near future.