Pressure gradients within the central nervous system.

The existence of clinically relevant pressure gradients within the central nervous system (CNS) is the subject of ongoing debate. Such gradients, if they do exist, would have significant implications for intracranial pressure (ICP) monitoring and ICP management in traumatic brain injury. As summarised in this short review, there is considerable experimental and clinical evidence that ICP is not evenly distributed within the central nervous system. Larger clinical trials on the implications of ICP gradients are warranted to address questions on the correct placement of ICP probes and on ICP management. It seems paradoxical to develop and employ ever more sophisticated monitoring devices in traumatic brain injury, such as monitoring of CNS metabolites with microdialysis or near-infrared spectroscopy, while fundamental issues such as the existence of ICP gradients remain unresolved.