REGIONAL CEREBRAL BLOOD-FLOW, WHITE-MATTER ABNORMALITIES, AND CEREBROSPINAL-FLUID HYDRODYNAMICS IN PATIENTS WITH IDIOPATHIC ADULT HYDROCEPHALUS SYNDROME

Objectives-(1) to evaluate regional cerebral blood flow (rCBF) with si ngle photon emission computed tomography and Tc-99m-hexamethylpropylen eamine oxime in patients with the idiopathic adult hydrocephalus syndr ome (IAHS); (2) to examine regional cerebral blood flow (rCBF), gait, and psychometric functions before and after CSF removal (CSF tap test) ; (3) to assess abnormalities in subcortical white matter by MRI. Meth ods-Thirty one patients fulfilling the criteria for IAHS (according to history and clinical and neuroradiological examination) were studied. Quantified gait measurements, psychometric testing, and rCBF before a nd after removal of CSF were obtained. Pressure of CSF and CSF outflow conductance were investigated with a constant pressure infusion metho d. Brain MRI was used to quantify the severity of white matter lesions and periventricular hyperintensities. In IAHS a widespread rCBF hypop erfusion pattern was depicted, with a caudal frontal and temporal grey matter and subcortical white matter reduction of rCBF as the dominant feature. Removal of CSF was not accompanied by a concomitant increase in rCBF. Significant white matter lesions were detected only in a min ority of patients by MRT. An altered CSF hydrodynamic state with a hig her Neurology CSF pressure and lower conductance was confirmed. IAHS i s characterised by an abnormal CSF hydrodynamic state, associated with a widespread rCBF reduction with preference for subcortical white mat ter and frontal-temporal cortical regions. Furthermore in most patient s MRT did not show white matter changes suggestive of a coexistent sub cortical arteriolosclerotic encephalopathy. At least in the idiopathic group of patients with AHS, measurements of rCBF before and after tem porary relief of the CSF hydrodynamic disturbance will not provide add itional information that would be helpful in the preoperative evaluati on but is suggestive of a preserved autoregulation of rCBF.