Early evaluation of cerebral metabolic rate of glucose (CMRglu) with 18F-FDG PET/CT and clinical assessment in idiopathic normal pressure hydrocephalus (INPH) patients before and after ventricular shunt placement: preliminary experience

Brain positron emission tomography in idiopathic normal-pressure hydrocephalus: new 18 F-fluorodeoxyglucose pattern in a long-known syndrome

AIM

Patients with idiopathic normal-pressure hydrocephalus (iNPH) can show a global reduction in cerebral glucose metabolism at [ 18 F]Fluorodeoxyglucose (FDG) PET. The presence of caudate hypometabolism has been identified as a potential biomarker in iNPH, yet there is limited evidence of hypermetabolic findings in patients with iNPH so far.

METHODS

We retrieved retrospectively patients with iNPH and normal cognitive assessment, evaluated before surgery undergoing brain [ 18 F]FDG-PET. The 18 F-FDG-PET brain scans were compared to those of a control group of healthy subjects, matched for age and sex, by statistical parametric mapping (SPM) to identify areas of relative hypo- and hypermetabolism. Furthermore, the existence of a correlation between areas of hypo- and hypermetabolism in the patient group was tested.

RESULTS

Seven iNPH patients (mean age 74 ± 6 years) were found in the hospital database. SPM group analysis revealed clusters of significant hypometabolism ( P  = 0.001) in the iNPH group in the dorsal striatum, involving caudate and putamen bilaterally. Clusters of significant hypermetabolism ( P  = 0.001) were revealed in the bilateral superior and precentral frontal gyrus (BA 4, 6). A significant inverse correlation between striatal hypometabolism and bilateral superior and precentral frontal gyrus hypermetabolism was revealed ( P  < 0.001 corrected for multiple comparisons).

CONCLUSION

In this cohort, patients with iNPH showed subcortical hypometabolism, including bilateral dorsal striatum. To the best of our knowledge, this is the first report demonstrating a hypermetabolic pattern in the primary motor and premotor areas, and showing an inverse correlation between the striatum and motor cortex in patients with iNPH.

The PUMCH Evaluation System of Idiopathic Normal Pressure Hydrocephalus and Clinical Practice

OBJECTIVE

Differentiating idiopathic normal pressure hydrocephalus (iNPH) from other neurodegenerative diseases is challenging. Only a portion of the patients clinically suspected of iNPH would respond to surgical intervention. A cerebrospinal fluid (CSF) tap test is usually used to predict surgery outcomes and hence aid clinical decision-making, but the workup varies. We introduce the CSF tap test conducted at our center and examine its power by analyzing data from a series of iNPH cases that underwent shunt placement. We analyze common features in the past medical history of our patients and investigate whether they are related to the etiology of iNPH.

METHODS

Data from 20 patients who were positive in the tap tests preoperatively and received ventriculoperitoneal shunting (VPS) were retrospectively analyzed. Preoperative and postoperative performance data were analyzed. History of any underlying medical conditions was taken into consideration. Patients with negative tap test results of the same period were also followed up.

RESULTS

We performed VPS placement in 20 NPH patients from October 2019 to February 2022. Of these, 90% exhibited improvement in at least 1 of the clinical triad, proving the predictive power of the Peking Union Medical College Hospital test workflow. The underlying conditions like hypertension, diabetes and insufficiency in cerebral blood supply were also found to be associated with the onset of NPH.

CONCLUSION

Our evaluation system is a valid tool for NPH assessment and can guide clinical decision-making. Comorbidities should be taken into consideration as they contribute to the pathogenesis and progression of NPH. Better identification of potential iNPH patients will lower the burden exerted on the family and the aging society.

Radiological biomarkers of idiopathic normal pressure hydrocephalus: new approaches for detecting concomitant Alzheimer's disease and predicting prognosis

Idiopathic normal pressure hydrocephalus (iNPH) is a clinical syndrome characterized by cognitive decline, gait disturbance, and urinary incontinence. As iNPH often occurs in elderly individuals prone to many types of comorbidity, a differential diagnosis with other neurodegenerative diseases is crucial, especially Alzheimer's disease (AD). A growing body of published work provides evidence of radiological methods, including multimodal magnetic resonance imaging and positron emission tomography, which may help noninvasively differentiate iNPH from AD or reveal concurrent AD pathology in vivo. Imaging methods detecting morphological changes, white matter microstructural changes, cerebrospinal fluid circulation, and molecular imaging have been widely applied in iNPH patients. Here, we review radiological biomarkers using different methods in evaluating iNPH pathophysiology and differentiating or detecting concomitant AD, to noninvasively predict the possible outcome postshunt and select candidates for shunt surgery.

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus

Among the various disorders that manifest with gait disturbance, cognitive impairment, and urinary incontinence in the elderly population, idiopathic normal pressure hydrocephalus (iNPH) is becoming of great importance. The first edition of these guidelines for management of iNPH was published in 2004, and the second edition in 2012, to provide a series of timely, evidence-based recommendations related to iNPH. Since the last edition, clinical awareness of iNPH has risen dramatically, and clinical and basic research efforts on iNPH have increased significantly. This third edition of the guidelines was made to share these ideas with the international community and to promote international research on iNPH. The revision of the guidelines was undertaken by a multidisciplinary expert working group of the Japanese Society of Normal Pressure Hydrocephalus in conjunction with the Japanese Ministry of Health, Labour and Welfare research project. This revision proposes a new classification for NPH. The category of iNPH is clearly distinguished from NPH with congenital/developmental and acquired etiologies. Additionally, the essential role of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) in the imaging diagnosis and decision for further management of iNPH is discussed in this edition. We created an algorithm for diagnosis and decision for shunt management. Diagnosis by biomarkers that distinguish prognosis has been also initiated. Therefore, diagnosis and treatment of iNPH have entered a new phase. We hope that this third edition of the guidelines will help patients, their families, and healthcare professionals involved in treating iNPH.

Diabetes is associated with familial idiopathic normal pressure hydrocephalus: a case-control comparison with family members

BACKGROUND

The pathophysiological basis of idiopathic normal pressure hydrocephalus (iNPH) is still unclear. Previous studies have shown a familial aggregation and a potential heritability when it comes to iNPH. Our aim was to conduct a novel case-controlled comparison between familial iNPH (fNPH) patients and their elderly relatives, involving multiple different families.

METHODS

Questionnaires and phone interviews were used for collecting the data and categorising the iNPH patients into the familial (fNPH) and the sporadic groups. Identical questionnaires were sent to the relatives of the potential fNPH patients. Venous blood samples were collected for genetic studies. The disease histories of the probable fNPH patients (n = 60) were compared with their ≥ 60-year-old relatives with no iNPH (n = 49). A modified Charlson Comorbidity Index (CCI) was used to measure the overall disease burden. Fisher's exact test (two-tailed), the Mann-Whitney U test (two-tailed) and a multivariate binary logistic regression analysis were used to perform the statistical analyses.

RESULTS

Diabetes (32% vs. 14%, p = 0.043), arterial hypertension (65.0% vs. 43%, p = 0.033), cardiac insufficiency (16% vs. 2%, p = 0.020) and depressive symptoms (32% vs. 8%, p = 0.004) were overrepresented among the probable fNPH patients compared to their non-iNPH relatives. In the age-adjusted multivariate logistic regression analysis, diabetes remained independently associated with fNPH (OR = 3.8, 95% CI 1.1-12.9, p = 0.030).

CONCLUSIONS

Diabetes is associated with fNPH and a possible risk factor for fNPH. Diabetes could contribute to the pathogenesis of iNPH/fNPH, which motivates to further prospective and gene-environmental studies to decipher the disease modelling of iNPH/fNPH.

Usefulness of Brain Positron Emission Tomography with Different Tracers in the Evaluation of Patients with Idiopathic Normal Pressure Hydrocephalous

Idiopathic normal pressure hydrocephalus (iNPH) is the only form of dementia that can be cured by surgery. Its diagnosis relies on clinical and radiological criteria. Identifying patients who can benefit from surgery is challenging, as other neurological diseases can be concomitant or mimic iNPH. We performed a systematic review on the role of positron emission tomography (PET) in iNPH. We retrieved 35 papers evaluating four main functional aspects with different PET radiotracers: (1) PET with amyloid tracers, revealing Alzheimer's disease (AD) pathology in 20-57% of suspected iNPH patients, could be useful in predictions of surgical outcome. (2) PET with radiolabeled water as perfusion tracer showed a global decreased cerebral blood flow (CBF) and regional reduction of CBF in basal ganglia in iNPH; preoperative perfusion parameters could predict surgical outcome. (3) PET with 2-Deoxy-2-[18F]fluoroglucose ([18F]FDG ) showed a global reduction of glucose metabolism without a specific cortical pattern and a hypometabolism in basal ganglia; [18F]FDG PET may identify a coexisting neurodegenerative disease, helping in patient selection for surgery; postsurgery increase in glucose metabolism was associated with clinical improvement. (4) Dopaminergic PET imaging showed a postsynaptic D2 receptor reduction and striatal upregulation of D2 receptor after treatment, associated with clinical improvement. Overall, PET imaging could be a useful tool in iNPH diagnoses and treatment response.

Cortical metabolic changes and clinical outcome in normal pressure hydrocephalus after ventriculoperitoneal shunt: Our preliminary results

INTRODUCTION

Our objective was to evaluate the cortical metabolic changes and clinical outcome in patients affected by idiopathic normal pressure hydrocephalus (iNPH) after a placement of ventriculoperitoneal (VP) shunt.

MATERIALS AND METHODS

10 patients affected by suspected iNPH underwent a CSF hydrodynamics evaluation based on a lumbar infusion test (LIT). The main selection criterion for surgery was based on intracranial elasticity (IE)>0.30. All subjects with an IE>0.30 underwent a PET scan with 18 fluorodeoxiglucose (¹⁸F-FDG) at baseline (PET1) and 1 month after surgery (PET2). Furthermore, the same patients were submitted to clinical evaluation before and 1 month after surgery through neuropsychological tests and gait analysis.

RESULTS

An overall number of 20 18F-FDG PET scans were performed in all the enrolled patients. As compared to PET1, PET2 showed an increase in glucose consumption in the left frontal and left parietal lobe in PET2 as compared to PET1 (P<.001). All the enrolled patients presented a significant increase in neuropsychological scores (i.e Frontal Assessment Battery and Montreal Cognitive Assessment) and have clinically improved at gait analysis. A significant correlation was found between the increase of cortical glucose consumption in the left parietal area and the cognitive improvement as detectable by neuropsychological assessment.

CONCLUSIONS

Improvement in 18F FDG PET glucose metabolism could be considered a useful imaging marker for the assessment of iNPH response to VP shunting.

Management of idiopathic normal pressure hydrocephalus (iNPH) - a retrospective study

Background: Normal pressure hydrocephalus (NPH) is communicating hydrocephalus characterised by normal intraventricular pressures. It presents with the triad of gait impairment, cognitive decline, and urinary incontinence. The term idiopathic normal pressure hydrocephalus (iNPH) is used in cases where the etiology is unknown. The aim of this study was to assess the prevalence and management of iNPH in our institution.Method: This was a retrospective study carried out at a tertiary health care center. Retrospective case series analysis was conducted using the existing electronic medical record data (2009-2017) on patients with hydrocephalus.Results: Forty-two (6.7%) patients with iNPH were identified, mean age 71.5 ± 8.8 years, 21 male (mean age 71.5 ± 9.3 years) and 21 female (mean age 71.5 ± 8.5 years). Ataxia was recorded in 39, symptoms of dementia in 31, and urinary incontinence in 29 patients. Forty patients were treated surgically by placing a ventriculoperitoneal (VP) shunt. One of the two patients treated by endoscopic third ventriculostomy (ETV) was subsequently treated by placing a VP shunt due to clinical deterioration. Significant improvements were noticed in cognitive and urinary symptoms, in the triad symptom sum score on the Japanese NPH scale, as well as in Evans' index and callosal angle (CA) on brain MRI (p < 0.05). Significant positive correlation was found between age and gait disturbance (Spearman's rho = 49.86% p = 0.0017), age and incontinence (Spearman's rho = 35.22%, p = 0.0351), age and triad symptom sum score (Spearman's rho = 44.67%, p = 0.0056), female gender and dementia (Spearman's rho = 34.94%, p = 0.0367), and among all three variables on the Japanese NPH scale (p < 0.0001).Conclusions: Treatment of iNPH with VP shunt showed significant improvement. A properly designed study is required to address the efficacy of ETV in the treatment of iNPH.

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.

The correlation between striatal and cortical binding ratio of 11C-PiB-PET in amyloid-uptake-positive patients

PURPOSE

In subjects with amyloid deposition, striatal accumulation of ¹¹C-Pittsburgh compound B (PiB) demonstrated by positron emission tomography (PET) is related to the stage of Alzheimer's disease (AD). In this study, we investigated the correlation between striatal and cortical non-displaceable binding potential (BP_ND).

METHODS

Seventy-three subjects who complained of cognitive disturbance underwent dynamic PiB-PET studies and showed positive PiB accumulation were retrospectively selected. These subjects included 34 AD, 26 mild cognitive impairment, 2 frontotemporal lobar degeneration, 2 Parkinson's disease, 5 dementia with Lewy bodies, and 4 undefined diagnosis patients. Individual BP_ND images were produced from the dynamic data of the PiB-PET study, and voxel-based analyses were performed to estimate the correlations between striatal and other regional cortical BP_ND measures.

RESULTS

There were highly significant correlations between striatal and prefrontal BP_ND, with the highest correlation being demonstrated in left Brodmann area 11. We found that almost all of the high cortical BP_ND values correlated with striatal BP_ND values, with the exception of the occipital cortex with low correlation.

CONCLUSION

Our study demonstrated positive correlations in amyloid deposits between the striatum and other cortical areas with functional and anatomical links. The amyloid distribution in the brain is not random, but spreads following the functional and anatomical connections.

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.

PET approaches for diagnosis of dementia

There is increasing use of neuroimaging modalities, including PET, for diagnosing dementia. For example, FDG-PET demonstrates hypometabolic regions in the posterior cingulate gyri, precuneus, and parietotemporal association cortices, while amyloid PET indicates amyloid deposition in Alzheimer disease and mild cognitive impairment due to Alzheimer disease. Furthermore, the use of combination PET with structural MR imaging can improve the diagnostic accuracy of dementia. In other neurodegenerative dementias, each disease exhibits a specific metabolic reduction pattern. In dementia with Lewy bodies, occipital glucose metabolism is decreased, while in frontotemporal dementia, frontal and anterior temporal metabolism is predominantly decreased. These FDG-PET findings and positive or negative amyloid deposits are important biomarkers for various neurodegenerative dementias.