Cerebral blood flow in patients with normal-pressure hydrocephalus before and after shunting

Abstract

Cerebral blood flow (CBF) was measured by xenon-133 inhalation and single photon emission tomography in 17 demented patients with normal-pressure hydrocephalus before and after shunt treatment. All patients had a decreased conductance to outflow (C out) of cerebrospinal fluid as measured by lumboventricular perfusion (C out less than 0.12 ml X mm Hg-1 X min-1). Computerized tomography (CT) scanning, clinical assessment, and neuropsychological grading were performed pre- and postoperatively. The preoperative CBF studies revealed abnormal flow patterns in all patients. Fourteen patients showed moderate-sized, large, or very large central low-flow areas, and four patients had reduced flow bilaterally in the occipital and contiguous temporoparietal regions. After shunting, six patients had a significant reduction in the size of the central low-flow area on the CBF map, agreeing well with the changes of ventricular size on the CT scan. All six patients showed an improvement in either clinical or neuropsychological grading. In 10 of the remaining 11 patients flow patterns were essentially unchanged; one patient deteriorated further. Four of these 11 patients improved on postoperative clinical or neuropsychological testing. Thus, a positive correlation was found between the changes in CBF and the reduction of the ventricular size on the CT scan, but changes in CBF as measured by the present technique did not accompany improvement in the functional state in all patients.

The Pathophysiology of Idiopathic Normal Pressure Hydrocephalus: Cerebral Ischemia or Altered Venous Hemodynamics?

“…9 Most popular theories interpret the CBF reduction found in NPH to be secondary to the degree of ventricular dilation. 9 The literature, however, indicates that whereas a direct correlation between reduced CBF and ventricular size has been suggested in some studies, 10,11 others have refuted this finding. 12, 13 Mathew et al 14 suggested that dilation of the ventricular system stretches the anterior cerebral arteries over the corpus callosum, thereby reducing flow.…”

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus Guidelines From the Guidelines Committee of Idiopathic Normal Pressure Hydrocephalus, the Japanese Society of Normal Pressure Hydrocephalus

“…57) There are many studies showing an association between improved symptoms and increased CBF after shunt procedure, 54B,70,74,118,128) but the contradictory result has been reported. 128) CSF tap test reveals no changes in CBF in normal controls, but some studies show an increase of CBF in NPH including iNPH. 70,114) A voxel-based analysis study reported a significant CBF increase in the bilateral dorsolateral frontal and left mesiotemporal cortices after the tap test.…”

“…These findings are supported by other studies. 57,70,74,76,117,128) A PET study reported the mean CBF decreased in the cerebrum and cerebellum with regional decrease in the basal ganglia and thalamus but not in the white matter. 82) There are few studies supporting the correlation between reduced flow and degree of symptoms.…”

Functional Magnetic Resonance Imaging Before and After Ventriculoperitoneal Shunting for Hydrocephalus. Case Report.

“…6,16) The improvement of cerebral blood flow (CBF) after VP shunting has been frequently discussed as a potent mechanism of symptom improvement. 25,30) However, CBF improvement alone does not necessarily lead to the symptomatic resolution. 18,30) Cerebral metabolism studies with positron emission tomography of glucose utilization 10,13,27,31) and oxygen utilization 2) have also revealed that reduction of periventricular metabolism is a common finding in untreated hydrocephalus.…”

“…25,30) However, CBF improvement alone does not necessarily lead to the symptomatic resolution. 18,30) Cerebral metabolism studies with positron emission tomography of glucose utilization 10,13,27,31) and oxygen utilization 2) have also revealed that reduction of periventricular metabolism is a common finding in untreated hydrocephalus. However, postoperative increases in metabolism are not always seen despite clinical improvement.…”