Change in regional cerebral blood flow following glycerol administration predicts

Abstract

Cerebral haemodynamics were measured in 22 adult patients with secondary normal pressure hydrocephalus (NPH) before and after glycerol administration to determine which patients might benefit from a shunt procedure. Of these 22 patients, 14 were found to be shunt-responsive (group 1) and 8 were shunt-unresponsive (group 2). Measurement of regional cerebral blood flow (rCBF) was performed by xenon-enhanced computerized tomography (XeCT). Clinical factors such as the Evans' index and the presence or absence of brain atrophy, periventricular lucency (PVL), ventricular reflux, stagnation of cerebrospinal fluid on cisternography, and increased intracranial pressure were not statistically significant predictors of shunt responsiveness. Preoperative rCBF values did not differ between groups 1 and 2. The rCBF value in every cerebral region of group 1 patients increased significantly after shunting except for the basal ganglia. On preoperative rCBF measurement, all rCBF values in group 1 significantly increased after glycerol administration except for the periventricular lucency (PVL). Patients in group 2, however, lacked such an increase in rCBF. We therefore propose that, in patients with secondary NPH, shunt surgery will be likely to be effective in those with a demonstrated rise in rCBF after glycerol administration.

Voxel-based assessment of spinal tap test-induced regional cerebral blood flow changes in normal pressure hydrocephalus

“…Different methods of cerebral perfusion imaging, such as xenon measurements [1,4,[11][12][13][14], 99m Tc-hexamethylpropylene amine oxime single photon emission computed tomography ( 99m Tc-HMPAO SPECT) [15], 99m Tc-ethyl cysteinate dimer ( 99m Tc-ECD) SPECT [16] and 123 Iisopropyl amphetamine ( 123 I-IAMP) SPECT [6], have shown a positive correlation between increased cerebral blood flow after CSF tap test and clinical improvement after CSF shunting procedures. However, conflicting results have been reported [17,18].…”

Cerebral hemodynamics before and after shunting in normal pressure hydrocephalus

“…Others believe that a fall in cerebral blood flow is a secondary phenomenon resulting from a decrease in cerebral metabolism caused by a decrease in volume of brain tissue in normal pressure hydrocephalus (19–21). Some authors have found no alterations in cerebral hemodynamics after shunt therapy (6–8, 16), whereas others found significant improvement in cerebral blood flow (9–11) and cerebrovascular reactivity (7, 10–12), and a reduction in PI (13). A remarkable observation in our study was the decrease in blood flow velocities in patients with and without clinical improvement after shunt surgery, suggestive for a possible postoperative normalization in intraparenchymal pressure and concomitant relaxation of large arteries.…”

“…A global cerebral blood flow reduction, more severe in the frontal lobes, has been observed in patients with normal pressure hydrocephalus (9, 16). This reduction in cerebral blood flow in patients with NPH is considered a result of increased intraparenchymal pressure in the brain with compression of small‐calibre vessels (10, 17, 18). Others believe that a fall in cerebral blood flow is a secondary phenomenon resulting from a decrease in cerebral metabolism caused by a decrease in volume of brain tissue in normal pressure hydrocephalus (19–21).…”

“…Whether changes in cerebral hemodynamics eventually lead to clinical improvement is unclear. The pathophysiologic mechanism underlying clinical improvement after shunt surgery in NPH is still unknown, and may include restoration of regional cerebral blood flow (7, 9–11, 16) and metabolic improvement (18). Higher preoperative cerebral blood flow, measured by means of single photon emission computed tomography, in patients with a favourable outcome has been observed (22).…”

“…Data on cerebral hemodynamics in normal pressure hydrocephalus are scarce and information on changes in cerebral hemodynamics induced by shunt surgery, are conflicting. Some authors have found no changes in one or more cerebral hemodynamic parameters after shunt surgery (6–8), whereas others did find significant improvement in cerebral blood flow (9–11), cerebrovascular reactivity (7, 10–12), and a concomitant decrease in pulsatility index (13). Whether these changes in cerebral hemodynamics are associated with clinical improvement is unknown.…”