NON-INVASIVE MONITORING OF INTRACRANIAL PRESSURE AND COMPLIANCE
Introduction: Increasing intracranial pressure (ICP) is one of the most dangerous complications following acute stroke. Monitoring of ICP provides the physician with data for rational treatment management but to date this must be carried out by invasive methods which carry a considerable risk of serious complications. Methods: In this study we have assessed a new non-invasive method for measuring ICP and compliance in 10 healthy controls. ICP variations were assessed by measuring tympanic membrane ICP propagation using a specially designed pressure transducer. Cerebral compliance was measured by simultaneously assessing the Windkessel volume displacement of the cerebral arteries. This is achieved by measuring the cross-section transcranial Doppler power index in the middle cerebral arteries with corrections for the Doppler frequency distributions (frequency corrected power). ICP was increased step-wise using a tilt-table (11–12 measurements in all subjects). This increases cerebral venous pressure which is the hydrostatic pressure relative to the right atrium and is known to be transformed into an equivalent ICP increase due to the valve function of the bridging veins. Compliance was calculated at each ICP value. Results: The pressure increases measured by tympanic membrane propagation and the calculated ICP increases showed a linear relationship in all 10 subjects. Compliance curves also showed typical decreases in compliance with increasing ICP. Conclusion: This study has shown that it is now possible to non-invasively monitor intracranial pressure and compliance. This new method should be assessed in extensive clinical studies.