Validation of Non-invasive Absolute Intracranial Pressure Monitoring

Primary objective of this study is to assess the accuracy and precision of intracranial pressure (ICP) measurement in patients after traumatic brain injury and subarachnoid hemorrhage when using simultaneous, non-invasive measurement compared to standard, invasive, measurement. Secondary objective: is to assess the correlation of intracranial pressure (ICP) measurement in patients after traumatic brain injury and subarachnoid hemorrhage between simultaneous, non-invasive measurement and standard, invasive,measurement