Determining an Accurate External Reference Point for Zeroing an External Ventricular Drain (EVD) as an Intracranial Pressure Monitoring System.

BACKGROUND: Monitoring of intracranial pressure is a highly valued tool in neurosurgical practice. There is no consensus about the exact outer zero point for correlation with the brain center while measuring the intracranial pressure using external ventricular drainage system. OBJECTIVE: The aim of this study was to evaluate the accuracy of using the top of the head serving as the zero-reference point of the intracranial pressure monitoring device and correlate its relation to the foramen of Monro at clinically used positions of the head. PATIENTS AND METHODS: The study included 30 patients who were candidates for invasive intracranial pressure monitoring with external ventricular drain for different pathological reasons. We compared two points as a zero-reference point; the glabella and the tragus as approximation to the foramen of Monro in different head positions. RESULTS: Readings while using the tragus were slightly higher than those while using the glabella as regards the intracranial pressure and drained higher cerebrospinal fluid volumes, with no statistically significant difference. CONCLUSION: Our study revealed that a zero point at the foramen of Monro was found to be insignificantly different from using the glabella as the zero-reference point when the head of the patient was positioned either supine or elevated 45°. [ABSTRACT FROM AUTHOR]