Quantitative analysis of CSF flow dynamics using MRI in normal pressure hydrocephalus

In order to clarify the flow dynamics of cerebrospinal fluid (CSF) in normal pressure hydrocephalus (NPH), a phase-contrast cine magnetic resonance (MR) imaging technique with retrospective cardiac gating was used to measure the quantitative flow velocity of CSF in the aqueduct in patients with NPH after subarachnoid hemorrhage (SAH-NPH group, n = 17), idiopathic NPH (1-NPH group, n = 2), asymptomatic ventricular dilatation or brain atrophy (VD group, n = 7) and healthy volunteers (control group, n = 19). Intracranial pressure (ICP) and pressure volume response (PVR) were also measured during the shunt operation in six of the SAH- NPH group. The maximum CSF flow velocity (Vmax) in the aqueduct was significantly larger in the SAH-NPH group (9.21 +/- 4.12 cm/sec, mean +/- SD) than in the control group (5.27 +/- 1.77, p < 0.001) and the VD group (4.06 +/- 1.81, p < 0.005). Vmax was not different between the control and VD groups. There was a positive correlation between the PVR and the peak CSF flow velocity in the SAH-NPH group. These findings suggest that the changes of CSF flow velocity in the SAH-NPH group might be caused by a moderate decrease of intracranial compliance. The CSF flow study using MRI is useful to differentiate NPH from brain atrophy or asymptomatic ventricular dilatation and also to estimate the intracranial compliance.