Abstract
Purpose
To assess the state and dynamics of the intracranial system in idiopathic normal‐pressure hydrocephalus (I‐NPH), we determined intracranial compliance using magnetic resonance imaging (MRI).
Materials and Methods
The intracranial compliance index (ICCI), which was defined as the ratio of the peak‐to‐peak intracranial volume change (ICVC~p‐p~) to the peak‐to‐peak cerebrospinal fluid (CSF) pressure gradient (PG~p‐p~) during the cardiac cycle, was obtained from the net transcranial blood and CSF flow measured with phase‐contrast (PC) cine MRI. ICCI was determined in patients with I‐NPH (N = 7), brain atrophy, or asymptomatic ventricular dilation (VD) (N = 6), and in healthy volunteers (control group; N = 11). The changes in ICCI indices were also analyzed after a CSF tap test (N = 2).
Results
The ICCI in the I‐NPH group was significantly lower than in the control and VD groups, whereas no difference was found between the control and VD groups. The ICVC~p‐p~ was also lower than in the control and VD groups. However, no significant difference was found in the PG~p‐p~ between groups. The ICCI increased after the tap test.
Conclusion
Intracranial compliance analysis with MRI makes it possible to noninvasively obtain more detailed information of intracranial biomechanics in the I‐NPH and to assist in the diagnosis of I‐NPH. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.