ICP Monitoring and Phase-Contrast MRI to Investigate Intracranial Compliance

Objective: The amplitude of intracranial pressure (ICP) can be measured by ICP monitoring. Phase-contrast magnetic resonance imaging (PCMRI) can quantify blood and cerebrospinal fluid (CSF) flows. The aim of this work was to investigate intracranial compliance at rest by combining baseline ICP monitoring and PCMRI in hydrocephalus patients. Materials and methods: ICP monitoring was performed before infusion testing to quantify Delta ICP_rest at the basal condition in 33 suspected hydrocephalus patients (74 years). The day before, patients had had a PCMRI to assess total cerebral blood flow (tCBF), intracranial blood volume change (stroke volume SVblood), and cervical CSF volume change (the stroke volume CSV). Global (blood and CSF) intracranial volume change (Delta IVC) during each cardiac cycle (CC) was calculated. Finally, Compliance: C_rest = Delta IVC/Delta ICP_rest was calculated. The data set was postprocessed by two operators according to blind analysis. Results: Bland-Altman plots showed that measurements presented no significant difference between the two operators. Delta ICP_rest = 2.41 +/- 1.21 mmHg, tCBF = 469.89 +/- 127.54 mL/min, SVblood = 0.82 +/- 0.32 mL/cc, CSV = 0.50 +/- 0.22 mL/cc, Delta IVC = 0.44 +/- 0.22 mL, and C_rest = 0.23 +/- 0.15 mL/mmHg. There are significant relations between SVblood and CSV and also SVblood and tCBF. Conclusions: During "basal" condition, the compliance amplitude of the intracranial compartment is heterogeneous in suspected hydrocephalus patients, and its value is lower than expected! This new parameter could represent new information, complementary to conventional infusion tests. We hope that this information can be applied to improve the selection of patients for shunt surgery.