Fig. 3

The correlation between intracranial pressure (ICP) and brain volume serves as a valuable metric for assessing brain compliance. In instances characterized by high compliance (green line), alterations in brain volume do not precipitate a corresponding elevation in ICP. However, as brain volume continues to expand, compensatory mechanisms come into play; these mechanisms encompass the displacement of cerebrospinal fluid (CSF, i.e., rostral movement outside the cranial vault) and the reduction in the venous blood volume. Over time, these compensatory processes become progressively depleted, leading to a transition from a state of reduced compliance (orange line) to minimal compliance (red line). In this latter state, even minor fluctuations in brain volume can elicit significant increases in ICP. The integration of automated pupillometry, cerebral ultrasound and evaluation of ICP waveform holds the potential to aid in gauging the extent of brain compliance, thereby facilitating a more comprehensive understanding of cerebral dynamics