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Objective: In recent years, new devices for epidural pressure (EDP) measurement have been developed, with claims of improved accuracy. However, there have been no new data from simultaneous pressure measurements to reverse the skepticism regarding this technique., Methods: The reliability of EDP recording was investigated in 26 patients with severe head injuries, during simultaneous measurement of ipsilateral intraventricular pressure (IVP) or intraparenchymal pressure (IPP)., Results: Periods of simultaneous measurement ranged from 3.3 to 168 hours. Technical failure occurred in five cases. Clinically significant erroneous pressure values (defined as differences of >10 mm Hg between EDP and IVP or IPP, lasting for >10 min) occurred in 7 of 21 measurements (33%). In three of these seven cases (43%) the difference between the EDP and the IVP or IPP remained nearly stable throughout the period of observation, whereas in four cases (57%) significant drifting over time was observed. Analysis of the transfer function calculated for the first to sixth harmonics between the EDP and the IVP or IPP showed no significant differences between the pulse pressure waveforms, even when significant drifting of more than 20 mm Hg occurred., Conclusion: The reliability of EDP measurement has not improved, compared with 10 years ago. Using this technique, one must be aware of the possibility of overestimating intracranial pressure by more than 10 mm Hg and the possibility of significant drifting of EDP over time, which argues against the use of this method even for trend analysis.

Failure of intraventricular pressure (IVP) measurement in case of catheter blockage is believed to be eliminated by using intraventricular microtransducers. We report about an avoidable methodological error, which may affect the reliability of IVP measurement with these devices. Intraventricular fiberoptic or solid state devices were implanted in 43 patients considered to be at risk for catheter occlusion. Two different types were used: devices where the transducer is placed inside the ventriculostomy catheter (Type A), and devices where the transducer is integrated in the external surface of the catheter (Type B). Of the 15 patients treated with Type A devices, no reliable pressure recording could be obtained in three patients where ventricular puncture was not successful. In four cases of the remaining 12 patients, periods of erroneous pressure readings were revealed. After opening of CSF drainage, all Type A devices failed to reflect real IVP. In patients treated with Type B devices, no erroneous pressure recording could be identified, irrespective if CSF drainage was performed or not. Transducers, which are simply placed inside the ventriculostomy catheter require fluid coupling. They may fail, either during CSF drainage or when the catheter is blocked or placed within the parenchyma.