Pathophysiology of Cerebral Circulatory Disorders in Idiopathic Normal Pressure Hydrocephalus

Abstract

This study was conducted to elucidate the pathologic conditions of cerebral circulatory disorders in idiopathic normal pressure hydrocephalus (iNPH). Among 44 possible iNPH patients, 40 patients underwent shunt surgery based on diagnostic flow charts plotted by the Southern Tohoku method and were evaluated to be shunt-effective at the end of the first post-surgical month. The cerebral blood flow (CBF) was measured by N-isopropyl-( 123 I)-P-iodo-amphetamine single photon emission computed tomography (mean, mCBF; cortical region, cCBF; thalamus-basal ganglia region, tbCBF on autoradiography [ARG] method) and the perfusion patterns of the cerebral cortex were measured based on threedimensional stereotactic surface projection (3D-SSP) Z-score images, before and 1 month after the surgery in all 40 subjects. The mCBF rose significantly from 32.1 ± 2.74 ml/100 g/min before surgery to 39.8 ± 3.02 ml/100 g/min after surgery (p º 0.03). Investigation of the change of CBF revealed reductions in the cCBF (3 cases), tbCBF (9 cases), and cCBF ＋ tbCBF (28 cases), with the reduced-cCBF group totaling 31 cases and the reduced-tbCBF group totaling 37 cases. Investigation of cerebral cortex hypoperfusion by 3D-SSP Z-score revealed 31 cases with hypoperfusion (frontal lobe type [19 cases], occipitotemporal lobe type [5 cases], mixed type [7 cases]) and nine cases with cortical normoperfusion (N). The pattern of reduction of the cortical blood flow on ARG method was favorably correlated with the pattern of hypoperfusion of the cerebral cortex on 3D-SSP Z-score images before surgery. A reduction of blood flow was found in the thalamus-basal ganglia region of all N type cases. The blood flow improved in 19 of 31 (61.3%) cases of the reduced-cCBF group and in 32 of 37 (86.5%) cases of the reducedtbCBF group. All of the cases without detectable improvement exhibited increased blood flow in nonreduction areas. Investigation of the hypoperfusion patterns of the cerebral cortex on 3D-SSP Z-score images, revealed a reduction or disappearance of the hypoperfusion site in 19 of 31 (61.3%) cases, either no-change or a shift of the hypoperfusion site in 12 of 31 (38.7%) cases, and a correlation between the pattern of cortical blood flow reduction on ARG method and the pattern of cerebral cortex hypoperfusion on 3D-SSP Z-score images after surgery. Cerebral circulatory disorders in iNPH manifest as either of two pathophysiological conditions: the``circulatory disorder of the cerebral cortical region'' and thè`c irculatory disorder of the thalamus-basal ganglia region.'' Various patterns develop according to the disease stage.

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus: Second Edition

“…Measurements of CBF in NPH, including patients with iNPH, have been conducted by single photon emission computed tomography utilizing radio-labeled materials including iodine-123 Nisopropyl-p-iodoamphetamine, 101,116,128) technetium99m hexamethylpropyleneamine oxime, 29,74,93) and technetium-99m ethyl cysteinate dimer, 47,67,143) positron emission tomography with 15 O-gas 97) and 15 O-H 2 O, 65,66) and nonradioactive xenon-CT. 130) In a study measuring CBF, hypoperfusion around the corpus callosum and sylvian fissures was observed and frontal dominant hypoperfusion has been reported in many studies, but posterior and diffuse hypoperfusion have also been reported. 67,74,116,129,143) When voxel-based analysis is performed, hypoperfusion around the sylvian fissures and the corpus callosum reflects dilation of the sylvian fissures and lateral ventricles, respectively.…”

“…116) There are many studies showing an association between improved symptoms and increased CBF after a shunt procedure 47,74,78,93,95,128,129) ; however, other studies report no association between the symptoms and CBF. 66) It was reported that regional CBF in iNPH patients with minimal triad symptoms was significantly lower than in healthy controls, but in all brain regions, there was no significant difference from those with apparent objective triad symptoms.…”

Global cerebral hypoperfusion in preclinical stage of idiopathic normal pressure hydrocephalus

“…Both ventriculomegaly and a narrowed subarachnoid at the high convexity are observed in brain magnetic resonance (MR) images in about one percent of normal elderly subjects as well as in patients with iNPH [2]. Quantitative regional cerebral blood flow (rCBF) seemed to be reduced in iNPH patients [3], which raises the question whether quantitative rCBF is also reduced in patients with pre-clinical stage iNPH.…”

Basilar Apex Aneurysm Manifesting as Third Ventricular Mass and Obstructive Hydrocephalus -Case Report-

“…1) Cerebral circulatory disorders in patients with NPH can manifest as either of two pathophysiological conditions: circulatory disorder of the cerebral cortical region, and that of the thalamus-basal ganglia region, and various patterns may develop according to the disease stage. 15) Such discrepant explanations may derive from the absence of comprehensive understanding of NPH, which is actually a dynamic and divergent disease in Neurol Med Chir (Tokyo) 48, October, 2008 S. Tsutsumi et al…”