Hydrodynamic and Hemodynamic Interactions in Chronic Hydrocephalus

During a cardiac cycle, intracranial pressure is related to arterial entry into the cranium and its interaction with intracranial compliance. The arterial inflow is compensated by intracranial compliance and, initially, the flushing of cerebrospinal fluid (CSF) into the cervical subarachnoid spaces. Our objective is to analyze the interactions between intracranial arteriovenous exchange and cerebrospinal fluid oscillations.

A total of 23 patients (73 ± 8 years) with suspected chronic hydrocephalus (CH) underwent an infusion test and phase-contrast MRI. Rout is an important factor in the diagnosis of CH. Patients were divided into 2 populations: probableCH (Rout: resistance to CSF outflow) (Rout > 12 mmHg/mL/min, 13 patients) and unlikelyCH (Rout < 12 mmHg/mL/min, 10 patients). We measured the intracranial vascular volume (arteriovenous stroke volume: SV_vasc) and CSF (CSF stroke volume at upper cervical level: SV_CSF) volume variations during the cardiac cycle.

In the whole population, we observed a significant correlation between SV_vasc and SV_CSF (R² = 0.43; p = 0.0007). In the population unlikelyCH, this correlation was significant (R² = 0.76; p = 0.001). In the population probableCH, this correlation was not significant (R² = 0.17, p = 0.16).

These results show that the link between the compliance of the oscillating CSF and the abrupt arterial inflow seems to be altered in CH. CSF oscillations between intracranial and cervical fluid spaces limit the impact of the abrupt arterial inflow.