Global cerebral hypoperfusion in preclinical stage of idiopathic normal pressure hydrocephalus. J Neurol Sci. 2010;298:35-41. [PMID: 20864126 DOI: 10.1016/j.jns.2010.09.001]

Changes in cerebral glucose metabolism caused by morphologic features of prodromal idiopathic normal pressure hydrocephalus

Background

Decreased cerebral glucose metabolism has been reported in idiopathic normal pressure hydrocephalus (iNPH). However, the timing of appearance in the preclinical stage of iNPH remains unknown. Herein, we evaluated the changes in regional cerebral glucose metabolism with respect to the characteristic morphologic features of iNPH.

Methods

We performed a cross-sectional study in > 2000 elderly patients who received a whole body 18F-fluorodeoxyglucose-positron emission tomography/computed tomography scanning and recruited subjects with clinical and preclinical iNPH. We included 12 subjects with iNPH, 32 subjects with asymptomatic ventriculomegaly with features of iNPH on magnetic resonance imaging (AVIM), and 33 subjects with preclinical morphologic features of DESH (PMD). We previously reported that iNPH develops in the order of PMD (asymptomatic subjects with incomplete DESH), AVIM (asymptomatic subjects with DESH), and iNPH (symptomatic subjects with DESH). We measured the median regional standardized uptake value ratio (SUVR) on 18F-fluorodeoxyglucose-positron emission tomography/computed tomography images between the three groups and compared them with background-matched normal controls in the frontal lobes, temporal lobes, medial parietal lobes, striata, and thalami.

Results

In the frontal and temporal lobes, the SUVR distributions of the PMD, AVIM, and PMD groups were significantly lower than for each NC (p < 0.05 for all). In the medial parietal lobes, the SUVR distributions were significantly higher in PMD and AVIM groups (p < 0.05 for all). In the thalami and striata, the SUVR distributions were significantly lower in the iNPH group (p < 0.05 for all).

Conclusions

Changes in brain glucose metabolism in the cortices are observed in preclinical iNPH, while metabolic decline in the basal ganglia is only detected in clinical iNPH.

Changes in brain morphology in patients in the preclinical stage of idiopathic normal pressure hydrocephalus

BACKGROUND

Specific ventriculomegaly features, including tight high-convexity and medial subarachnoid spaces, are found on magnetic resonance images in patients with idiopathic normal pressure hydrocephalus (iNPH). However, some healthy elderly individuals with no typical triad symptoms of iNPH also exhibit specific magnetic resonance image features of iNPH. Therefore, this study quantitatively clarified the brain morphology of suspected iNPH patients with no objective triad symptoms (iNPH-NOS).

METHODS

We recruited patients with suspected iNPH and divided them into two groups based on their iNPH grading scale scores: the iNPH-NOS group and the iNPH with apparent objective triad symptoms (iNPH-AOS) group. Data for normal controls (NC) were taken from the database used in our previous study. We compared the relative volumes of ventricle systems (VS), Sylvian fissures (SF), and sulci at high convexity and the midline (SHM), adjusted by the intracranial volume, of the iNPH-NOS, iNPH-AOS, and NC groups. Additionally, we compared the relative volumes of VS, SF, and SHM in iNPH-NOS patients between their first visit and follow-up 1 year later.

RESULTS

Fifteen iNPH-NOS patients and 45 iNPH-AOS patients were recruited, and 24 NCs were found in the database. The relative volumes of VS and SF were significantly smaller than in NCs than in the iNPH-NOS and iNPH-AOS groups, and the relative volume of SHM was significantly larger in NCs. The relative volume of SHM was significantly larger in the iNPH-NOS group than in the iNPH-AOS group, but there were no significant differences in the relative volumes of VS and SF between these groups. In the iNPH-NOS group, the relative volumes of VS and SF were significantly smaller at the first visit than 1 year later, whereas the relative volume of SHM was significantly larger. In 6 of 15 iNPH-NOS patients, objective symptoms appeared during the observation period.

CONCLUSIONS

Our results indicate that iNPH-NOS patients were in the transitional stage between normal and iNPH-AOS, both morphologically and clinically.

Cerebral blood flow and Alzheimer's disease-related biomarkers in cerebrospinal fluid in idiopathic normal pressure hydrocephalus

AIM

Alzheimer's disease (AD) pathology is highly prevalent in patients with idiopathic normal pressure hydrocephalus (iNPH), and the presence of AD pathology may involve regional cerebral blood flow (rCBF). In this study, we examined the relationship between rCBF and AD-related biomarkers in the cerebrospinal fluid of iNPH patients.

METHODS

Patients with iNPH (n = 39) were classified into groups with (iNPH/AD+) (n=15) and without (iNPH/AD-) (n=24) high biomarker probability of AD (i.e. combined low amyloid β 42 and high total tau in the cerebrospinal fluid). rCBF was quantified in 17 regions of interest by N-isopropyl-p-[¹²³ I]iodoamphetamine single-photon emission computed tomography with the autoradiography method. We compared rCBF between the iNPH/AD- and iNPH/AD+ groups at baseline using a t-test and then compared changes in rCBF after shunt surgery between the groups using a paired t-test and two-way repeated measures ANOVA.

RESULTS

At baseline, there were no significant differences in rCBF between the groups in most regions apart from the putamen. After shunt surgery, a significant increase in rCBF in the putamen, amygdala, hippocampus, and parahippocampal gyrus was observed in iNPH/AD- patients. In iNPH/AD+ patients, no significant improvement in rCBF was observed in any region. In repeated measures analysis of variance, a significant group × shunt interaction was observed in the parietal lobe, frontal lobe, posterior cingulate cortex, precuneus, lateral temporal lobe, amygdala, hippocampus, parahippocampal gyrus, and putamen.

CONCLUSIONS

Improvement in rCBF after shunt surgery in iNPH/AD+ patients may be poorer than that in iNPH AD- patients.

Usefulness of the convexity apparent hyperperfusion sign in 123I-iodoamphetamine brain perfusion SPECT for the diagnosis of idiopathic normal pressure hydrocephalus

OBJECTIVE

The gold standard for the diagnosis of idiopathic normal pressure hydrocephalus (iNPH) is the CSF removal test. For elderly patients, however, a less invasive diagnostic method is required. On MRI, high-convexity tightness was reported to be an important finding for the diagnosis of iNPH. On SPECT, patients with iNPH often show hyperperfusion of the high-convexity area. The authors tested 2 hypotheses regarding the SPECT finding: 1) it is relative hyperperfusion reflecting the increased gray matter density of the convexity, and 2) it is useful for the diagnosis of iNPH. The authors termed the SPECT finding the convexity apparent hyperperfusion (CAPPAH) sign.

METHODS

Two clinical studies were conducted. In study 1, SPECT was performed for 20 patients suspected of having iNPH, and regional cerebral blood flow (rCBF) of the high-convexity area was examined using quantitative analysis. Clinical differences between patients with the CAPPAH sign (CAP) and those without it (NCAP) were also compared. In study 2, the CAPPAH sign was retrospectively assessed in 30 patients with iNPH and 19 healthy controls using SPECT images and 3D stereotactic surface projection.

RESULTS

In study 1, rCBF of the high-convexity area of the CAP group was calculated as 35.2–43.7 ml/min/100 g, which is not higher than normal values of rCBF determined by SPECT. The NCAP group showed lower cognitive function and weaker responses to the removal of CSF than the CAP group. In study 2, the CAPPAH sign was positive only in patients with iNPH (24/30) and not in controls (sensitivity 80%, specificity 100%). The coincidence rate between tight high convexity on MRI and the CAPPAH sign was very high (28/30).

CONCLUSIONS

Patients with iNPH showed hyperperfusion of the high-convexity area on SPECT; however, the presence of the CAPPAH sign did not indicate real hyperperfusion of rCBF in the high-convexity area. The authors speculated that patients with iNPH without the CAPPAH sign, despite showing tight high convexity on MRI, might have comorbidities such as Alzheimer’s disease.

11C-PIB retention patterns in white and grey cerebral matter in idiopathic normal pressure hydrocephalus patients. A visual analysis

OBJECTIVE

Cortical cerebral amyloid disease, a hallmark of Alzheimer's disease, has also been observed in idiopathic normal pressure hydrocephalus (iNPH). The aim of this study was to compare the ¹¹C-PIB PET/CT retention pattern in iNPH patients and healthy subjects.

MATERIAL AND METHODS

A comparison was made of the ¹¹C-PIB PET/CT retention pattern in 13 iNPH patients selected for surgical deviation, compared to a normal control population. Images were visually analyzed and scored for gray matter and white matter (WM) from 1 to 4 (slight to very high PIB retention). The scoring was analyzed in both groups separately for infra- and supra-tentorial regions. A comprehensive clinical report was presented in terms of positive, negative, or equivocal.

RESULTS

¹¹C-PIB PET/CT scan were reported as negative in 8, positive in 3, and equivocal in 2. Five of 13 patients showed at least one cortical area with PIB retention with an intensity higher than that observed in the control group. Overall, white matter (WM) PIB retention of iNPH scored lower than in the control group, showing a statistically significant difference in the infratentorial WM (92/104 vs 54/56; p<.05) and a tendency to be lower in the supratentorial regions (70/84 vs 122/156, p=.327), in particular in the upper periventricular region (25/28 vs 40/52; p=.134).

CONCLUSIONS

The PIB retention pattern seems to be different in NPH, compared to normal subjects. PIB retention in WM of NPH appears less intense than in healthy subjects, and they show a higher degree of PIB retention in cortical regions. This deserves to be taken it into account.

Pre-and postoperative cerebral blood flow changes in patients with idiopathic normal pressure hydrocephalus measured by computed tomography (CT)-perfusion

In idiopathic normal pressure hydrocephalus (iNPH), the cerebral blood flow (CBF) is of pathophysiological interest and a potential biomarker. Computed tomography perfusion (CTP), an established technique with high spatial resolution and quantitative measurements, has not yet been used in the iNPH context. If CTP were sensitive to the CBF levels and changes in iNPH, this technique might provide diagnostic and prognostic absolute perfusion thresholds. The aim of this work was to determine the applicability of CTP to iNPH. CBF measurements of 18 patients pre- and 17 three months postoperatively, and six healthy individuals (HI) were evaluated in 12 cortical and subcortical regions of interest. Correlations between CBF and symptomatology were analyzed in shunt-responders. Compared to HI, the preoperative CBF in iNPH was significantly reduced in normal appearing and periventricular white matter (PVWM), the lentiform nucleus and the global parenchyma. No CBF differences were shown between responders and non-responders. In responders, the CBF recovered postoperatively by 2.5-32% to approximately the level of HI, but remained significantly decreased in the PVWM of non-responders. The pre- and postoperative CBF of cortical and subcortical regions correlated with the intensity of symptoms. In spite of limited spatial coverage, CTP can measure CBF changes in iNPH.

A review of cognitive impairment and differential diagnosis in idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a complex and still underestimated pathology. In the early stages, the cognitive profile is characterized mainly by impairments of attention, psychomotor speed and memory, suggesting frontal involvement; patients with more advanced iNPH show overall cognitive deterioration. The memory impairment, however, seems to be milder than that seen in Alzheimer's disease (AD). Clinical and neuroimaging data are crucial for the diagnosis of iNPH, but the presence of different variables, such as comorbidities, and the possible overlapping with other neurodegenerative diseases, AD in particular, make the differential diagnosis difficult. To date studies seeking to identify possible biological markers have provided inconclusive results; moreover reliable indices predictive of a good response to surgery are still lacking. There is a need for further studies with longer follow-ups and for closer interaction among the different professionals involved.

Current concepts on the pathophysiology of idiopathic chronic adult hydrocephalus: Are we facing another neurodegenerative disease?

INTRODUCTION

Since its description five decades ago, the pathophysiology of idiopathic chronic adult hydrocephalus (iCAH) has been traditionally related to the effect that ventricular dilatation exerts on the structures surrounding the ventricular system. However, altered cerebral blood flow, especially a reduction in the CSF turnover rate, are starting to be considered the main pathophysiological elements of this disease.

DEVELOPMENT

Compression of the pyramidal tract, the frontostriatal and frontoreticular circuits, and the paraventricular fibres of the superior longitudinal fasciculus have all been reported in iCAH. At the level of the corpus callosum, gliosis replaces a number of commissural tracts. Cerebral blood flow is also altered, showing a periventricular watershed region limited by the subependymal arteries and the perforating branches of the major arteries of the anterior cerebral circulation. The CSF turnover rate is decreased by 75%, leading to the reduced clearance of neurotoxins and the interruption of neuroendocrine and paracrine signalling in the CSF.

CONCLUSIONS

iCAH presents as a complex nosological entity, in which the effects of subcortical microangiopathy and reduced CSF turnover play a key role. According to its pathophysiology, it is simpler to think of iCAH more as a neurodegenerative disease, such as Alzheimer disease or Binswanger disease than as the classical concept of hydrocephalus.

Idiopathic normal pressure hydrocephalus: cerebral perfusion measured with pCASL before and repeatedly after CSF removal

Pseudo-continuous arterial spin labeling (pCASL) measurements were performed in 20 patients with idiopathic normal pressure hydrocephalus (iNPH) to investigate whether cerebral blood flow (CBF) increases during the first 24 hours after a cerebrospinal fluid tap test (CSF TT). Five pCASL magnetic resonance imaging (MRI) scans were performed. Two scans were performed before removal of 40 mL CSF, and the other three at 30 minutes, 4 hours, and 24 hours, respectively after the CSF TT. Thirteen different regions of interest (ROIs) were manually drawn on coregistered MR images. In patients with increased CBF in lateral and frontal white matter after the CSF TT, gait function improved more than it did in patients with decreased CBF in these regions. However, in the whole sample, there was no significant increase in CBF after CSF removal compared with baseline investigations. The repeatability of CBF measurements at baseline was high, with intraclass correlation coefficients of 0.60 to 0.90 for different ROIs, but the median regional variability was in the range of 5% to 17%. Our results indicate that CBF in white matter close to the lateral ventricles plays a role in the reversibility of symptoms after CSF removal in patients with iNPH.

Comprehensive urodynamics: Being devoted to clinical urologic practice

As a combined electrophysiological system for evaluating the lower urinary tract (LUT), comprehensive urodynamics (UDS) aims at duplicating patient’s micturition process, either normal or abnormal, and further seeking for possible causative origin, either neurogenic or non-neurogenic, in order to guide treatment. Through thorough analysis, some so-called cut-off values, for example, bladder outlet obstruction (BOO) degree or dyssynergic degree between the detrusor and sphincter, could be gained; however, in most cases, their qualitative description, such as stress urinary incontinence, idiopathic detrusor underactivity (DUA), detrusor overactivity (IDO), low compliance, and idiopathic sphincter overactivity (ISO), is more preferable and important. In aged neurologically intact male patients with symptoms of the LUT (LUTS) including benign prostatic hyperplasia, a combined UDS system, which coupled BOO with compliance, was constructed. The patients may be categorized into one of the seven subgroups, including equivocal or mild BOO with sphincter synergia with or without IDO (pattern A), equivocal or mild BOO with ISO (B), classic BOO with sphincter synergia (C) or ISO (D), BOO with only low compliance (E), BOO with both DUA and low compliance (F), and potential BOO with DUA (G). This new system can be used to optimize diagnosis and treatment according to a derived guideline diagram.

Normal pressure hydrocephalus as a failure of ICP homeostasis mechanism: the hidden role of Monro-Kellie doctrine in the genesis of NPH

OBJECTIVE

The theme of this paper is to outline that the genesis of normal pressure hydrocephalus (NPH) is governed by the intracranial pressure (ICP) homeostatic principle. The development of this new concept is based mainly on rethinking the well-known Monro-Kellie doctrine in the way that ICP homeostasis mechanism is not only a mechanism that works to prevent pathologically high ICP but also a mechanism that aims to protect from pathologically low ICP.

METHODS

The NPH-related literatures are reviewed and reinterpreted to generate a new paradigm for the cascade of pathophysiological events that leads to the genesis NPH, as well as the mechanism of clinical beneficial effects and complications of the shunting procedure.

RESULTS

According to this new paradigm, the suboptimal cerebral perfusion that is associated with the impairment of the cerebral autoregulation is the initial step in the genesis of NPH. When the overall volume of blood that circulates intracranially is diminished, a chronic low ICP with episodes of pathologically low ICP occurs. Since the cranial vault is not collapsible, those episodes of low ICP are compensated by the accumulation of cerebrospinal fluid (CSF) to keep the ICP in normal ideal range. The impairment of brain toxin-flushing mechanism because of CSF pooling combined with the already-established suboptimal cerebral perfusion leads to functional disinhibition of the cerebral cortex.

CONCLUSION

Recognizing the importance of ICP homeostatic mechanisms in the genesis of the NPH is a simple yet novel view that could change the way we look at NP and can give a basic and fundamental theoretical frame work to achieve better understanding of NPH.

Preoperative acetazolamide SPECT is useful for predicting outcome of shunt operation in idiopathic normal pressure hydrocephalus patients

PURPOSE OF THE REPORT

Good outcome of shunt surgery for idiopathic normal pressure hydrocephalus (iNPH) patients are highly dependent on accurate preoperative assessments. Acetazolamide ethylcysteinate-dimer-single photon emission computer tomography (SPECT) was applied to iNPH patients for more exact preoperative evaluation.

PATIENTS AND METHODS

Sixty-five patients were categorized into 3 groups: group I (normals, n = 30), group II (with ventriculomegaly due to age-relating changes, n = 10), and group III (who underwent shunt surgery based on the diagnosis of iNPH, n = 25). Acetazolamide SPECT was performed in all patients, and mini-mental state examination (MMSE) was performed before and 1 month after the surgery in group III.

RESULTS

Acetazolamide SPECT study demonstrated normal increase of cerebral blood flow (CBF, more than 40%) in groups I and II. Group III was classified into 2 subgroups on the examination; a mean increasing percentage (%increase) of CBF was less than 20% in group IIIa and more than 40% in group IIIb. One month after the surgery, acetazolamide SPECT showed normal %increase of CBF in IIIa, and the increase in postoperative MMSE score was significantly greater in group IIIa than IIIb (P < 0.05). In iNPH patients, less than 20% increase in preoperative acetazolamide SPECT predicted improvement of MMSE score with 100% sensitivity and 60% specificity.

CONCLUSIONS

Poor %increase of CBF by acetazolamide implies a low capacity for vasodilation in the brain due to compression and stretching by ventriculomegaly. Acetazolamide SPECT study is not an absolute examination but one of the valuable supplementary objective examinations to determine the surgical indication in iNPH-suspected patients.

Memantine treatment for neuropsychiatric symptoms in a patient with probable idiopathic normal pressure hydrocephalus: a case report

Introduction

Patients with idiopathic normal pressure hydrocephalus often show neuropsychiatric symptoms besides the triad of ‘classic’ symptoms. Memantine has been reported to have positive effects on the neuropsychiatric symptoms of patients with Alzheimer’s disease and patients with dementia with Lewy bodies. We administered memantine to a Japanese patient with probable idiopathic normal pressure hydrocephalus, hoping that this treatment would have positive effects on the neuropsychiatric symptoms of his idiopathic normal pressure hydrocephalus.

Case presentation

An 80-year-old right-handed Japanese man was diagnosed as having probable idiopathic normal pressure hydrocephalus and showed neuropsychiatric symptoms as well as the triad of classic symptoms of idiopathic normal pressure hydrocephalus. We treated our patient with memantine by increasing, decreasing, and then again increasing the dose of memantine. We evaluated his neuropsychiatric symptoms using the Neuropsychiatric Inventory at baseline, after the dose was increased to 20mg/day, after the dose was decreased to 5mg/day, and after the dose was increased again to 15mg/day. We simultaneously evaluated the triad of symptoms and conducted neuropsychological tests. In addition, we evaluated the psychological distress of our patient’s caregiver using the Zarit Caregiver Burden Interview.

Conclusions

Memantine had positive effects on the neuropsychiatric symptoms of our patient with idiopathic normal pressure hydrocephalus. Although none of his triad of classic symptoms, including cognitive abilities, improved, the psychological distress of our patient’s caregiver improved.

Reversibility of brain morphology after shunt operations and preoperative clinical symptoms in patients with idiopathic normal pressure hydrocephalus

AIM

Brain deformations might prevent clinical symptoms from worsening in patients with idiopathic normal pressure hydrocephalus (iNPH). We investigated the relationship between reversibility of brain morphology after shunt operations and preoperative clinical symptoms in iNPH patients.

METHODS

Using head magnetic resonance images with voxel-based morphometry, we measured the cerebrospinal fluid volume in the combined areas of the lateral and third ventricles and Sylvian fissure (the volume of the ventricles and Sylvian fissure (vVS)) and the volume of the subarachnoid space at high convexity and midline areas (vHCM) before and 1 year after lumboperitoneal shunt operations in 12 patients with shunt-responsive iNPH. We used the ratio of normalized vVS to normalized vHCM (nvVS/nvHCM) as an index of the severity of the brain deformation. The degree of reversibility of the brain morphology after the shunt operation was defined as the change ratio of the preoperative nvVS/nvHCM to the postoperative nvVS/nvHCM (CR-nvVS/nvHCM). Higher CR-nvVS/nvHCM values indicated more improvement in the brain deformation. In addition, we rated the severity of the white matter lesions on the preoperative magnetic resonance images based on the Fazekas scale. Dependency in activities of daily living, gait and cognition were evaluated before and 1 year after the shunt operations.

RESULTS

After the shunt operations, the nvVS/nvHCM and nvVS decreased significantly, and nvHCM increased significantly. The CR-nvVS/nvHCM negatively correlated with the preoperative severity of dependency in activities of daily living, gait and cognitive impairments. The CR-nvVS/nvHCM negatively correlated with the Fazekas scale, but not with age, duration of the disease and cerebrospinal fluid pressure.

CONCLUSIONS

Reversibility of brain morphology, which varied among iNPH patients, would prevent clinical symptoms from worsening in iNPH patients. The presence of white matter lesions reduced the degree of reversibility of the brain deformations in iNPH patients.

Subclinical declines in the verbal fluency and motor regulation of patients with AVIM (asymptomatic ventriculomegaly with features of idiopathic NPH on MRI): a case-controlled study

OBJECTIVE

We previously reported that, on brain MRI, iNPH features were observed in approximately 1% of asymptomatic elderly community dwellers. This phenomenon is designated asymptomatic ventriculomegaly with features of iNPH on MRI (AVIM). The aim of the present study was to clarify whether a subclinical decline in the neuropsychological function is present in patients with AVIM.

METHODS

We examined eight subjects with AVIM, six subjects with possible iNPH and 21 elderly controls. Neuropsychological tests were used, including the mini-mental state examination (MMSE), the Hasegawa dementia scale-revised (HDS-R), the frontal assessment battery (FAB), the trail making test A&B and semantic and letter verbal fluency tests.

RESULTS

When comparing the individuals with AVIM with the control subjects, significant differences were found in the scores achieved on the semantic verbal fluency tests and Luria's motor series (fist-edge-palm), a subtest of the FAB.

CONCLUSION

The present study suggests that individuals with AVIM demonstrate a slight subclinical decline in the cognitive function and motor regulation, which may represent a prodromal stage of iNPH.

Cognitive profile of idiopathic normal pressure hydrocephalus

Background/Aims

Frontal lobe dysfunction is believed to be a primary cognitive symptom in idiopathic normal pressure hydrocephalus (iNPH); however, the neuropsychology of this disorder remains to be fully investigated. The objective of this study was to delineate a comprehensive profile of cognitive dysfunction in iNPH and evaluate the effects of cerebrospinal fluid (CSF) shunt surgery on cognitive dysfunction.

Methods

A total of 32 iNPH patients underwent neuropsychological testing of memory, attention, language, executive function, and visuoperceptual and visuospatial abilities. Of these 32 patients, 26 were reevaluated approximately 1 year following CSF shunt surgery. The same battery of tests was performed on 32 patients with Alzheimer's disease (AD) and 30 healthy elderly controls.

Results

The iNPH patients displayed baseline deficits in attention, executive function, memory, and visuoperceptual and visuospatial functions. Impairments of attention, executive function, and visuoperceptual and visuospatial abilities in iNPH patients were more severe than in those with AD, whereas the degree of memory impairment was comparable to that in AD patients. A significant improvement in executive function was observed following shunt surgery.

Conclusion

Patients with iNPH are impaired in various aspects of cognition involving both ‘frontal’ executive functions and ‘posterior cortical’ functions. Shunt treatment can ameliorate executive dysfunction.