Cerebral perfusion pressure (CPP) lower limits of reactivity can be determined almost continuously after severe traumatic brain injury (TBI), and deviation below the lower limit carries important prognostic information. In this study, we used a recently derived coloured contour method for visualizing intracranial pressure (ICP) insults to describe the influence of having a CPP above the CPP lower limits of reactivity after severe TBI. In a cohort of 729 patients, we examined the relationship between ICP insults and the 6-month Glasgow Outcome Scale score, using colour-coded plots, as described previously. We then assessed this relationship when ICP insults were above or below the CPP lower limit of reactivity. We found a curvilinear relationship whereby even prolonged durations of low-intensity ICP insults were not associated with poor outcomes but short durations of high-intensity insults were. When only ICP insults with a CPP below the CPP lower limit of reactivity were considered, a much lower intensity of ICP insults could be tolerated. A CPP above the lower limits of reactivity exerts a protective effect, whereas a CPP below the lower reactivity limits renders the patient vulnerable to increased morbidity from intracranial hypertension.