Abstract
Objectives: To evaluate the cerebrospinal fluid (CSF) dynamics in secondary normal pressure hydrocephalus (sNPH), we compared the three-dimensional velocities and volumes of reciprocating CSF movements and several shear stress parameters, measured by four-dimensional (4D) flow magnetic resonance imaging (MRI) among sNPH, hemorrhagic stroke, and control groups.
Methods: In this study, 4D flow MRI in the seven patients with sNPH, eight patients with acute hemorrhagic stroke who did not develop sNPH, and nine age-matched healthy controls were analyzed. The CSF stroke volumes and reversed flow rate at the 10 regions from the bilateral foramina of Monro to the foramen magnum were measured by using the 4D flow application on SYNAPSE VINCENT (FUJIFILM, Tokyo). In addition, oscillatory shear stress (OSS) and oscillatory shear index (OSI) at the dorsal and ventral sides of the cerebral aqueduct were calculated. The mean values of CSF stroke volumes, reversed flow rate, OSS amplitude, maximum and minimum values of OSS, and OSI were compared among the three groups.
Results: The sNPH group had significantly larger stroke volumes and higher reversed flow rates at the foramen of Magendie and lower end of the cerebral aqueduct, and larger stroke volumes at the upper end of the cerebral aqueduct and foramina of Monro than in the non-sNPH hemorrhagic stroke group and age-matched healthy controls. The amplitude and maximum value of OSS at the cerebral aqueduct were significantly higher in the hemorrhagic stroke group than in the controls.
Discussion: In the acute phase of hemorrhagic stroke, the CSF stroke volume at the cerebral aqueduct increases because of the decrease in brain compliance due to the increased intracranial pressure. We suggest that the increase in the OSS amplitude due to the increased CSF stroke volume promotes the dilation of ventricular walls.
Conclusions: Patients with acute hemorrhagic stroke had larger amplitudes and maximum values of OSS at the cerebral aqueduct than age-matched healthy controls. Furthermore, patients with sNPH had larger CSF stroke volumes at the bilateral foramina of Monro, upper and lower ends of the cerebral aqueduct, and foramen of Magendie, than did those with hemorrhagic stroke. Visualization of CSF movements and quantification of shear stress parameters on 4D flow MRI may help predict the development of sNPH.
