Vascular compliance in normal pressure hydrocephalus.

BACKGROUND AND PURPOSE Normal pressure hydrocephalus (NPH) is considered to be a combination of altered CSF resorption and a reversible form of cerebral ischemia. The hypothesis tested in this study was that a reduction in venous compliance in the territory drained by the superior sagittal sinus (SSS) is associated with NPH and cerebral ischemia. METHODS This prospective study involved 27 patients without evidence of hydrocephalus. This group was subdivided into those with normal MR findings and those with evidence of ischemia or atrophy. Ten patients with NPH then underwent MR flow quantification studies of the cerebral vessels. Five of these patients had the same studies performed after CSF drainage. Vascular compliance was measured in the SSS and straight sinus territory by use of MR flow quantification with net systolic pulse volume (NSPV) and arteriovenous delay (AVD) as markers. RESULTS Vascular compliance of patients with ischemia or atrophy was significantly higher than that of healthy subjects (mean NSPV in the SSS, 417 microL and 274 microL, respectively). Patients with NPH showed lower compliance than that of the healthy subjects in the SSS (mean NSPV, 212 microL and 274 microL, respectively; mean AVD, 42 ms and 89 ms, respectively). After intervention, the NPH group showed compliance approximating the group with ischemia/atrophy. CONCLUSION Vascular compliance is significantly different in the brains of healthy subjects as compared with that in patients with ischemia/atrophy or NPH.