Intracranial compliance is time-dependent.

Area of Science:

• Neurosurgery
• Neurology
• Physiology

Background:

• Intracranial compliance is a critical characteristic of the intracranial system.
• Intracranial compliance is typically measured using the volume pressure test (VPT).
• Intracranial compliance is thought to be related to cerebrospinal fluid (CSF) pulse pressure (delta Pcsf).

Purpose of the Study:

• To determine the time-dependent relationship of intracranial compliance.
• To investigate the relationship between intracranial pulse pressure and compliance.

Main Methods:

• Nine dogs were divided into two groups, with skull integrity altered (open or closed) to modify intracranial compliance.
• Volume pressure tests (VPT) were performed using slow infusion, fast infusion, and bolus injection methods.
• Relationships between diastolic CSF pressure (Pcsf-d), delta Pcsf, infusion rates, and CSF respiratory wave amplitude were analyzed.

Main Results:

• With the skull closed, linear relationships were observed between Pcsf-d and delta Pcsf, infusion methods, and CSF respiratory wave amplitude.
• With the skull open, linear relationships were maintained only for Pcsf-d vs. delta Pcsf and Pcsf-d vs. bolus injection.
• Cerebrospinal fluid pulse pressure amplitude remained consistent regardless of skull status at any given Pcsf-d level.

Conclusions:

• Intracranial compliance can be differentiated into two components based on the injected volume's time constant.
• Physical compliance, characterized by a short time constant, is associated with delta Pcsf.
• Physiological compliance, with a longer time constant, is related to the volume pressure test (VPT).