# Intracranial pressure following surgery of an unruptured intracranial aneurysm—a model for normal intracranial pressure in humans

## TL;DR

This study measures normal intracranial pressure in adults undergoing surgery for an unruptured aneurysm, providing new reference ranges and insights into pressure dynamics in different body positions.

## Contribution

The study presents novel normal intracranial pressure and pulse wave amplitude values in healthy adults across various postures.

## Key findings

- Median ICP was 6.7 mmHg in the supine position and -3.4 mmHg in the upright position.
- Median PWA was 2.1 mmHg in the supine position and 1.9 mmHg in the upright position.
- Standardized ICPmidbrain was 8.3 mmHg supine and 1.2 mmHg upright.

## Abstract

Optimizing the treatment of several neurosurgical and neurological disorders relies on knowledge of the intracranial pressure (ICP). However, exploration of normal ICP and intracranial pressure pulse wave amplitude (PWA) values in healthy individuals poses ethical challenges, and thus the current documentation remains scarce. This study explores ICP and PWA values for healthy adults without intracranial pathology expected to influence ICP.

Adult patients (age > 18 years) undergoing surgery for an unruptured intracranial aneurysm without any other neurological co-morbidities were included. Patients had a telemetric ICP sensor inserted, and ICP was measured in four different positions: supine, lateral recumbent, standing upright, and 45-degree sitting, at day 1, 14, 30, and 90 following the surgery.

ICP in each position did not change with time after surgery. Median ICP was 6.7 mmHg and median PWA 2.1 mmHg in the supine position, while in the upright standing position median ICP was − 3.4 mmHg and median PWA was 1.9 mmHg. After standardization of the measurements from the transducer site to the external acoustic meatus, the median ICPmidbrain was 8.3 mmHg in the supine position and 1.2 mmHg in the upright standing position.

Our study provides insights into normal ICP dynamics in healthy adults following a uncomplicated surgery for an unruptured aneurysm. These results suggest a slightly wider normal reference range for invasive intracranial pressure than previously suggested, and present the first normal values for PWA in different positions. Further studies are, however, essential to enhance our understanding of normal ICP.

Trial registration The study was preregistered at www.clinicaltrials.gov (NCT03594136) (11 July 2018)

The online version contains supplementary material available at 10.1186/s12987-024-00549-1.