Resistance to cerebrospinal fluid outflow versus “pseudo” intracranial compliances in hydrocephalus patients
Résumé
Introduction: The resistance to cerebrospinal fluid (CSF) outflow (Rout) has been considered as a complementary parameter to predict shunt responsiveness in patients with normal pressure hydrocephalus (NPH). Additionally, a “pseudo” intracranial compliance (Cinfus) can be defined by considering the change in intracranial pressure (ICP) in response to a known volume change injected during infusion test. We propose to also evaluate a physiological brain compliance (Cphysio) related to instantaneous intracranial volume (blood and CSF) change and ICP amplitude during the cardiac cycle. We aim to evaluate the relationship between these compliances and Rout.
Methods: 26 patients (74 ± 9 years) with suspected NPH underwent infusion test and PC-MRI. Cinfus was calculated by dividing the volume injected by the ICP change during infusion. From PC-MRI, the intracranial liquid volume change (blood and CSF) during the cardiac cycle (CC) was quantified. The ICP change in amplitude at rest over the CC was assessed from ICP monitoring before infusion. Changes in volume and pressure along the CC were used to calculate Cphysio. After infusion, Rout was estimated by ICM + .
Results: Correlations between compliances and Rout were respectively R2 = 0.24 (p < 0.05) and R2 = 0.012 (p < 0.05) for Cinfus and Cphysio.
Conclusions: These preliminary results show that Cinfus and Rout tend to have a higher correlation than Cphysio and Rout. Indeed, Cinfus reflects the brain capacity to respond to continuous volume injection over prolonged time, which could be associated mainly with Rout and venous compliance. Contrary, Cphysio reflects instantaneous physiological compliance of intracranial volume directly related to brain biomechanics.