1. ^*Academic Neurosurgery Unit, Addenbrooke's Hospital, Sydney, Australia
2. ^†Wolfson Brain Imaging Center, University of Cambridge, Cambridge, United Kingdom
3. ^§Brain Repair Center, University of Cambridge, Cambridge, United Kingdom
4. ^‡Department of Surgery, University of Sydney, Sydney, Australia

Correspondence: Brian K Owler, Institute of Clinical Neuroscience, Department of Neurosurgery, Royal Prince Alfred Hospital, Missenden Road, Camperdown NSW 2050, Australia; e-mail: brianowl@bigpond.com

Received 15 August 2003; Revised 5 November 2003; Accepted 31 December 2003.

Abstract

The combination of cerebral blood flow measurement using ¹⁵O-water positron emission tomography with magnetic resonance coregistration and CSF infusion studies was used to study the global and regional changes in CBF with changes in CSF pressure in 15 patients with normal pressure hydrocephalus. With increases in CSF pressure, there was a variable increase in arterial blood pressure between individuals and global CBF was reduced, including in the cerebellum. Regionally, mean CBF decreased in the thalamus and basal ganglia, as well as in white matter regions. These reductions in CBF were significantly correlated with changes in the CSF pressure and with proximity to the ventricles. A three-dimensional finite-element analysis was used to analyze the effects on ventricular size and the distribution of stress during infusion. To study regional cerebral autoregulation in patients with possible normal pressure hydrocephalus, a sensitive CBF technique is required that provides absolute, not relative normalized, values for regional CBF and an adequate change in cerebral perfusion pressure must be provoked.