Pattern of white matter regional cerebral blood flow and autoregulation in normal pressure hydrocephalus

Abstract

The mean cerebral blood flow (CBF) has generally been demonstrated to be lower in normal pressure hydrocephalus (NPH) than in normal controls. We investigated the distribution of the regional peri- and paraventricular white matter CBF (WM CBF) in NPH at baseline and during a controlled rise in intracranial pressure (ICP). Twelve patients with idiopathic NPH (mean age 69 years) underwent a CSF infusion study. CBF was measured by H2(15)O PET at baseline and then during the steady-state plateau of raised ICP. The PET images were co-registered and resliced to 3D structural T1-weighted MRIs. Ten healthy normal volunteers served as control subjects for baseline CBF determination only. Profiles of the regional distribution of the baseline WM CBF and of the percentage change in WM CBF as a function of distance from the ventricles were plotted. The global mean baseline CBF in patients (28.4 +/- 5.2 ml/100 ml/min) was lower than in the control subjects (33 +/- 5.4 ml/100 ml/min) (P < 0.005). In patients, the profile of the regional WM CBF at baseline showed an increase with distance from the ventricles (P < 0.0001), with a maximal reduction adjacent to the ventricles and progressive normalization with distance, whereas in controls no relationship was apparent (P = 0.0748). In 10 patients, the rise in ICP during the infusion produced a fall in cerebral perfusion pressure (CPP) and a significant decrease of the global mean CBF from 27.6 +/- 3.1 to 24.5 +/- 2.9 ml/100 ml/min (P < 0.0001). The profile of the percentage changes in regional WM CBF in patients showed a U-shaped relationship with distance from the ventricles (P = 0.0007), with a maximal decrease skewed on the side of the lateral ventricles at around a mean distance of 9 mm. The WM CBF is reduced in NPH, with an abnormal gradient from the lateral ventricles towards the subcortical WM. An excessive decrease in CBF is brought about by reductions in CPP and appears to be maximal in the paraventricular watershed region. These results are discussed in the light of previous hypotheses concerning the aetiology of periventricular CBF reduction in NPH.

Cerebral Autoregulation after Subarachnoid Hemorrhage: Comparison of Three Methods

“…36 However, NIRS measures surrogates of cerebral blood flow in the mixed arterio-venous compartment in cerebral cortex located in the watershed area between the MCA and anterior cerebral artery, where, in patients with normal pressure hydrocephalus, autoregulation has been suggested to be weaker. 37 Perhaps, this is why values of TOxa are lower than Sxa (Supplementary Table 1). The two modalities measure different anatomic regions of the brain as well as different vascular beds.…”

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

“…82,90) In a study measuring CBF in 31 patients of suspected Chapter 1: Diagnosis iNPH with 99m Tc-HMPAO SPECT, 54B) reduced blood flow over a wide area, especially in the cortex and subcortical white matter of the frontal and temporal lobes (expansion of central low-flow area), is seen. 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. 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.…”

“…54B) The involvement of autoregulatory impairment is still controversial. 70,74,82,118) Thus, CBF measurements can show diffuse or regional decrease of CBF in NPH, but they are insufficient for the definite diagnosis of iNPH and also insufficient for the indication of shunt surgery (Recommendation grade C). However, CBF studies are useful in differentiating iNPH from other disorders of dementia, including Alzheimer's disease.…”

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

“…The significant decrease in CBF in NPH patients is considered to result from reductions in cerebral perfusion pressure and appears to be maximal in the paraventricular watershed region. 10) In contrast, significant increases in CBF were recognized after CSF diversion in the left prefrontal dorsolateral areas, right frontal premotor area, right medial prefrontal region, right frontal white matter area, and right basal ganglia. 9) On the other hand, an overlap in the CBF volumes measured between patients with NPH and normal subjects suggested that ischemia may not be a prerequisite for this condition, but instead may reflect increased superficial venous pressure in patients with NPH.…”