[Possibilities of dynamic phase contrast MRI of cerebrospinal fluid for performing a tap test in a patient with idiopathic normotensive hydrocephalus]. / Vozmozhnosti dinamicheskoi fazovo-kontrastnoi MR-likvorografii pri vypolnenii tap-testa u patsienta s idiopaticheskoi normotenzivnoi gidrotsefaliei.

Idiopathic normotensive hydrocephalus (iNH) is a widespread disease in elderly patients. The effectiveness of iNG treatment and the subsequent quality of patients' lives directly depends on timely and early diagnosis. The criteria for diagnosing iNG that are used in neuroimaging can also be found in patients without clinical manifestations of this disease, and the widely used tap-test is an invasive technique with a rather low sensitivity. The need for early diagnosis and initiation of treatment before the development of irreversible damage to brain structures determines the relevance of the search for an accessible, minimally invasive, accurate and safe diagnostic method. The article presents a clinical observation of the use of phase-contrast MRI of cerebrospinal fluid (CSF) in a female patient with a positive response to the tap test with a quantitative analysis of changes in CSF flow parameters and ALVI and Evans indices depending on the time after CSF evacuation. Phase-contrast MRI of CSF with a quantitative assessment of CSF flow parameters in combination with an assessment of the ALVI index has the potential to increase the accuracy of diagnosing iNH and is of scientific interest for further research.

Freezing of gait in idiopathic normal pressure hydrocephalus.

BACKGROUND: Reports of freezing of gait (FoG) in idiopathic normal pressure hydrocephalus (iNPH) are few and results are variable. This study's objective was to evaluate the frequency of FoG in a large cohort of iNPH patients, identify FoG-associated factors, and assess FoG's responsiveness to shunt surgery. METHODS: Videotaped standardized gait protocols with iNPH patients pre- and post-shunt surgery (n = 139; median age 75 (71-79) years; 48 women) were evaluated for FoG episodes by two observers (Cohens kappa = 0.9, p < 0.001). FoG episodes were categorized. Mini-mental state examination (MMSE) and MRI white matter hyperintensities (WMH) assessment using the Fazekas scale were performed. CSF was analyzed for Beta-amyloid, Tau, and Phospho-tau. Patients with and without FoG were compared. RESULTS: Twenty-two patients (16%) displayed FoG at baseline, decreasing to seven (8%) after CSF shunt surgery (p = 0.039). The symptom was most frequently exhibited during turning (n = 16, 73%). Patients displaying FoG were older (77.5 vs. 74.6 years; p = 0.029), had a slower walking speed (0.59 vs. 0.89 m/s; p < 0.001), a lower Tinetti POMA score (6.8 vs. 10.8; p < 0.001), lower MMSE score (21.3 vs. 24.0; p = 0.031), and longer disease duration (4.2 vs. 2.3 years; p < 0.001) compared to patients not displaying FoG. WMH or CSF biomarkers did not differ between the groups. CONCLUSIONS: FoG is occurring frequently in iNPH patients and may be considered a typical feature of iNPH. FoG in iNPH was associated with higher age, longer disease duration, worse cognitive function, and a more unstable gait. Shunt surgery seems to improve the symptom.

[Recent Developments in Diagnostic Imaging for Idiopathic Normal Pressure Hydrocephalus].

Idiopathic normal pressure hydrocephalus (iNPH), a syndrome characterized by cognitive impairment, gait abnormalities, and urinary incontinence attributable to cerebrospinal fluid circulatory insufficiency, is associated with an obscure etiology. Several methodologies and imaging analysis techniques, including visualization of cerebral hemodynamics and diffusion tensor imaging have emerged in recent years to determine functional alterations in cases of iNPH. These advancements have led to more comprehensive understanding of the pathophysiological mechanisms underlying iNPH. In this article, we discuss the historical evolution of imaging modalities for iNPH and contemporaneous imaging techniques designed to acquire deeper insight into this disease.

Prevalence of Possible Idiopathic Normal Pressure Hydrocephalus in Sweden: A Population-Based MRI Study in 791 70-Year-Old Participants

BACKGROUND AND OBJECTIVES: Very divergent prevalence rates for idiopathic normal pressure hydrocephalus (iNPH) are reported, probably due to differences in study sample selection and diagnostic criteria. This MRI-based study aimed to determine the prevalence of iNPH and iNPH-specific radiologic changes and their association with clinical symptoms in a large, 70-year-old population-based cohort (Gothenburg H70). METHODS: In this cross-sectional study, disturbances in gait and balance, cognition, and urinary continence were assessed using clinical examination and self-report. MRI was evaluated for iNPH-specific imaging markers. iNPH was diagnosed according to International Guidelines (I.G.). Based on radiologic findings, participants were allocated to 1 of 4 groups: (A) Evans index (EI) ≤0.3 (reference), (B) EI >0.3 without other iNPH-typical radiologic findings, (C) radiologically probable iNPH according to I.G., and (D) radiologically holistically probable (h-probable) iNPH fulfilling radiologic criteria according to I.G. plus highly iNPH-specific changes according to an experienced neuroradiologist. RESULTS: The Gothenburg H70 Studies include 791 individuals (377 men, 414 women) born in 1944 who underwent brain MRI. The prevalence of iNPH was 1.5% (2.1% for men, 0.96% for women) according to I.G. Ninety participants (11%) had EI >0.3 without other iNPH-typical radiologic findings, 29 (3.7%) fulfilled the I.G. radiologic probable iNPH criteria alone, and 11 (1.4%) were classified as radiologically h-probable iNPH. Forty participants (5.1%) had I.G. radiologic features of iNPH (70% men vs 30% women, p = 0.005). Gait disturbances were more common in participants with EI >0.3 without other radiologic iNPH features (B) (33%) compared with the reference group (A) (19%) (p = 0.006). All clinical symptoms were more common in participants with I.G. radiologic features of iNPH (C + D) than they were in the reference group (A) (p < 0.03). DISCUSSION: The iNPH prevalence of 1.5% among 70-year-olds, which is considerably higher than earlier reported in this age group, suggests that iNPH may be more common than previously assumed. This is supported by the 5.1% total prevalence of imaging signs of iNPH. Ventriculomegaly without other iNPH-typical radiologic findings may be an early sign of developing iNPH in some patients.

Prediction of Surgical Outcomes in Normal Pressure Hydrocephalus by MR Elastography.

BACKGROUND AND PURPOSE: Normal pressure hydrocephalus is a treatable cause of dementia associated with distinct mechanical property signatures in the brain as measured by MR elastography. In this study, we tested the hypothesis that specific anatomic features of normal pressure hydrocephalus are associated with unique mechanical property alterations. Then, we tested the hypothesis that summary measures of these mechanical signatures can be used to predict clinical outcomes. MATERIALS AND METHODS: MR elastography and structural imaging were performed in 128 patients with suspected normal pressure hydrocephalus and 44 control participants. Patients were categorized into 4 subgroups based on their anatomic features. Surgery outcome was acquired for 68 patients. Voxelwise modeling was performed to detect regions with significantly different mechanical properties between each group. Mechanical signatures were summarized using pattern analysis and were used as features to train classification models and predict shunt outcomes for 2 sets of feature spaces: a limited 2D feature space that included the most common features found in normal pressure hydrocephalus and an expanded 20-dimensional (20D) feature space that included features from all 4 morphologic subgroups. RESULTS: Both the 2D and 20D classifiers performed significantly better than chance for predicting clinical outcomes with estimated areas under the receiver operating characteristic curve of 0.66 and 0.77, respectively (P < .05, permutation test). The 20D classifier significantly improved the diagnostic OR and positive predictive value compared with the 2D classifier (P < .05, permutation test). CONCLUSIONS: MR elastography provides further insight into mechanical alterations in the normal pressure hydrocephalus brain and is a promising, noninvasive method for predicting surgical outcomes in patients with normal pressure hydrocephalus.

[Clinical features and effects of shunt surgery in patients with progressive supranuclear palsy and idiopathic normal pressure hydrocephalus].

This study aimed to retrospectively review the frequency and clinical features of 13 patients with progressive supranuclear palsy (PSP) and idiopathic normal pressure hydrocephalus (iNPH). All patients were found to have PSP-Richardson's syndrome (PSP-RS). Shunt surgery was effective in 5 of 11 patients (45.5%). A comparison of these 5 patients who responded to shunt surgery versus the remaining 6 patients revealed a significant difference in the reduction of frontal lobe blood flow on cerebral perfusion single-photon emission computed tomography (SPECT) (P = 0.018). These results suggest that PSP-RS is common in patients with PSP and iNPH and indicate the usefulness of cerebral perfusion SPECT in estimating the effect of shunt surgery.

Patients with normal pressure hydrocephalus have fewer enlarged perivascular spaces in the centrum semiovale compared to cognitively unimpaired individuals.

INTRODUCTION: Enlarged perivascular spaces (ePVS) may be an indicator of glymphatic dysfunction. Limited studies have evaluated the role of ePVS in idiopathic normal pressure hydrocephalus (iNPH). We aimed to characterize the distribution and number of ePVS in iNPH compared to controls. METHODS: Thirty-eight patients with iNPH and a pre-shunt MRI were identified through clinical practice. Age- and sex-matched controls who had negative MRIs screening for intracranial metastases were identified through a medical record linkage system. The number of ePVS were counted in the basal nuclei (BN) and centrum semiovale (CS) using the Wardlaw method blinded to clinical diagnosis. Imaging features of disproportionately enlarged subarachnoid space hydrocephalus (DESH), callosal angle, Fazekas white matter hyperintensity (WMH) grade, and the presence of microbleeds and lacunes were also evaluated. RESULTS: Both iNPH patients and controls had a mean age of 74 ± 7 years and were 34% female with equal distributions of hypertension, dyslipidemia, diabetes, stroke, and history of smoking. There were fewer ePVS in the CS of patients with iNPH compared to controls (12.66 vs. 20.39, p < 0.001) but the same in the BN (8.95 vs. 11.11, p = 0.08). This remained significant in models accounting for vascular risk factors (p = 0.002) and MRI features of DESH and WMH grade (p = 0.03). CONCLUSIONS: Fewer centrum semiovale ePVS may be a biomarker for iNPH. This pattern may be caused by mechanical obstruction due to upward displacement of the brain leading to reduced glymphatic clearance.

Usefulness of third ventricle volumetry in patients with normal pressure hydrocephalus.

OBJECTIVE: To use third ventricle morphometric variables as a tool for the selection of patients with idiopathic normal pressure hydrocephalus (iNPH) who are candidates for ventriculoperitoneal shunts (VPS). MATERIAL AND METHODS: Retrospective study enrolling patients with iNPH. Katzman infusion test was performed and a Rout > 12 mmHg/mL/min was considered a positive result. The transverse diameter and the volume of the third ventricle were measured in the preoperative MRI. Postoperative improvement was assessed with the NPH score. The results were analysed with SPSS software. RESULTS: 52 patients with a mean age of 76 years were analysed. There was no difference in the diameter of the third ventricle among patients with a positive result and those with a negative result in the infusion test (12.28 vs 11.68 mm; p = 0.14). Neither were difference detected in the ventricle volume of both groups (3.6 vs 3.5cc; p = 0.66). Those patients who improved after VPS had a smaller third ventricle compared to those who did not respond after surgery (11.85 mm vs. 12.96 mm; p = 0.009). Diameter and volume of third ventricle present a significant strong correlation (Pearson correlation coefficient = 0.72; p < 0.0001). CONCLUSION: Morphometric variables of third ventricle may be useful in predicting a good response to VPS in patients with idiopathic normal pressure hydrocephalus.

Intraventricular Shunt Catheter Placement of Adult Normal Pressure Hydrocephalus Using an AxiEMTM Electromagnetic Neuronavigation System: A Single-Center Experience.

AIM: To prove the superiority of the electromagnetic (EM) neuronavigation technique to increase the accuracy of intraventicular shunt catheter placement, and to reduce accompanying complications. MATERIAL AND METHODS: A total of 21 patients with hydrocephalus [age range (years): 53-84] were studied. All of them had undergone thin-slice, navigation-compatible, computed tomography (CT) preoperatively. Shunt surgery was performed under the guidance of EM neuronavigation technology. All patients underwent follow-up CT the next day to evaluate catheter tip placement and were followed up at 1, 3, 6, and 12 months. RESULTS: All catheter tips were placed properly in front of the foramen of Monro in the desired position, except in one case in which the tip migrated to the perimesencephalic cistern and underwent reoperation in the early postoperative period. No complications due to infection and obstruction were observed in the medium- and long-term follow-ups. The complication rate due to the incorrect catheter positioning was 4.76% of the total cases. CONCLUSION: The placement of the ventricular catheter under EM-guided navigation technology reduces the proximal-end failure caused by malpositioning, obstruction, and infection.

Invasive Preoperative Investigations in Idiopathic Normal Pressure Hydrocephalus: A Comprehensive Review.

Idiopathic normal pressure hydrocephalus (iNPH) is a neurological disorder characterized by the triad of gait disturbance, cognitive impairment, and urinary incontinence. The condition is diagnosed mainly in older adults and is associated with ventricular enlargement without an increase in cerebrospinal fluid pressure. The clinical assessment involves a detailed medical history, physical examination, and cognitive testing. Neuroimaging is an essential part of the diagnostic workup for iNPH. However, to determine the suitability of patients for shunt surgery, a range of invasive preoperative investigations are employed. This narrative review aims to provide a comprehensive analysis of the current literature on invasive preoperative investigations in iNPH, focusing primarily on the lumbar infusion test, cerebrospinal fluid drainage tests, and continuous intracranial pressure monitoring. The strengths and limitations of each method, as well as their potential impact on treatment outcomes, are discussed.

Abnormal characteristic static and dynamic functional network connectivity in idiopathic normal pressure hydrocephalus.

AIMS: Idiopathic Normal pressure hydrocephalus (iNPH) is a neurodegenerative disease characterized by gait disturbance, dementia, and urinary dysfunction. The neural network mechanisms underlying this phenomenon is currently unknown. METHODS: To investigate the resting-state functional connectivity (rs-FC) abnormalities of iNPH-related brain connectivity from static and dynamic perspectives and the correlation of these abnormalities with clinical symptoms before and 3-month after shunt. We investigated both static and dynamic functional network connectivity (sFNC and dFNC, respectively) in 33 iNPH patients and 23 healthy controls (HCs). RESULTS: The sFNC and dFNC of networks were generally decreased in iNPH patients. The reduction in sFNC within the default mode network (DMN) and between the somatomotor network (SMN) and visual network (VN) were related to symptoms. The temporal properties of dFNC and its temporal variability in state-4 were sensitive to the identification of iNPH and were correlated with symptoms. The temporal variability in the dorsal attention network (DAN) increased, and the average instantaneous FC was altered among networks in iNPH. These features were partially associated with clinical symptoms. CONCLUSION: The dFNC may be a more sensitive biomarker for altered network function in iNPH, providing us with extra information on the mechanisms of iNPH.

Noninvasive assessment of glymphatic dysfunction in idiopathic normal pressure hydrocephalus with diffusion tensor imaging.

OBJECTIVE: Diffusion tensor imaging (DTI) along the perivascular space (ALPS) (DTI-ALPS)-by calculating the ALPS index, a ratio accentuating water diffusion in the perivascular space-has been proposed as a noninvasive, indirect MRI method for assessing glymphatic function. The main aim of this study was to investigate whether DTI-ALPS would reveal glymphatic dysfunction in idiopathic normal pressure hydrocephalus (iNPH) and whether the ALPS index was associated with disease severity. METHODS: Thirty iNPH patients (13 men; median age 77 years) and 27 healthy controls (10 men; median age 73 years) underwent MRI and clinical assessment with the Timed Up and Go test (TUG) and Mini-Mental State Examination (MMSE); only the patients were evaluated with the Hellström iNPH scale. MRI data were analyzed with the DTI-ALPS method and Radscale screening tool. RESULTS: iNPH patients showed significantly lower mean ALPS index scores compared with healthy controls (median [interquartile range] 1.09 [1.00-1.15] vs 1.49 [1.36-1.59], p < 0.001). Female healthy controls showed significantly higher ALPS index scores than males in both hemispheres (e.g., right hemisphere 1.62 [1.47-1.67] vs 1.33 [1.14-1.41], p = 0.001). This sex difference was not seen in iNPH patients. The authors found a moderate exponential correlation between mean ALPS index score and motor function as measured with time required to complete TUG (r = -0.644, p < 0.001), number of steps to complete TUG (r = -0.571, p < 0.001), 10-m walk time (r = -0.637, p < 0.001), and 10-m walk steps (r = -0.588, p < 0.001). The authors also found a positive linear correlation between mean ALPS index score and MMSE score (r = 0.416, p = 0.001). Simple linear regression showed a significant effect of diagnosis (B = -0.39, p < 0.001, R2 = 0.459), female sex (B = 0.232, p = 0.002, R2 = 0.157), and Evans index (B = -4.151, p < 0.001, R2 = 0.559) on ALPS index. Multiple linear regression, including diagnosis, sex, and Evans index score, showed a higher predictive value (R2 = 0.626) than analysis of each of these factors alone. CONCLUSIONS: The ALPS index, which was significantly decreased in iNPH patients, could serve as a marker of disease severity, both clinically and in terms of neuroimaging. However, it is important to consider the significant influence of biological sex and ventriculomegaly on the ALPS index, which raises the question of whether the ALPS index solely reflects glymphatic function or if it also encompasses other types of injury. Future studies are needed to address potential confounding factors and further validate the ALPS method.

Letter to Our Colleagues Family Practitioners, Geriatricians, and Radiologists to Increase Awareness Regarding Idiopathic Normal Pressure Hydrocephalus.

OBJECTIVE: Idiopathic normal pressure hydrocephalus (iNPH) affects elderly individuals and is characterized by a progressive deterioration of gait, urinary continence, and cognition. In most cases, it is reversible with treatment. INPH is not uncommonly an unrecognized cause of dementia. We wish to raise awareness of iNPH among primary care providers who are seeing these patients first. METHODS: We reviewed the current epidemiological data regarding iNPH as well as epidemiological data regarding Alzheimer disease. We searched for the most sensitive radiological screening test for iNPH. RESULTS: Alzheimer disease comprises 60%-70% of all dementia cases, in 2023 is affecting 6.7 million Americans, about 10.7% of people 65 and older. Epidemiological data from the Scandinavian countries confirmed that 3.7% of people older than 65 have iNPH. Surgical studies confirmed the presence of early Alzheimer's pathology in about 25% of operated patients with iNPH. Useful radiological findings of iNPH include an Evans Index greater than 0.30, and a disproportionally enlarged subarachnoid space hydrocephalus (DESH). However, the callosal angle is thought to represent the best tool to discriminate iNPH from its mimics. CONCLUSIONS: According to the available epidemiological data iNPH is underdiagnosed. We strongly encourage the primary care physicians and geriatricians to ask the radiologist to measure the callosal angle on the initial brain computed tomography (or magnetic resonance) image. If the callosal angle is ≤71°, it is appropriate to refer the patient to neurosurgery for further diagnostic work-up.

Evaluation of a Fully Automated Method for Ventricular Volume Segmentation Before and After Shunt Surgery in Idiopathic Normal Pressure Hydrocephalus.

BACKGROUND: Determination of the ventricle size in idiopathic normal pressure hydrocephalus (iNPH) is essential for diagnosis and follow-up of shunt results. Fully automated segmentation methods are anticipated to optimize the accuracy and time efficiency of ventricular volume measurements. We evaluated the accuracy of preoperative and postoperative ventricular volume measurements in iNPH by a magnetic resonance imaging (MRI)-based licensed software for fully automated quantitative assessment. METHODS: Forty-eight patients diagnosed with iNPH were retrospectively analyzed. All patients received a ventriculoperitoneal shunt and had symptom grading and routine MRI preoperatively and 3-6 months postoperatively. Ventricular volumes, generated by fully automated T1-weighted imaging volume sequence segmentation, were compared with semiautomatic measurements and routine radiologic reports. The relation of postoperative ventricular size change to clinical response was evaluated. RESULTS: Fully automated segmentation was achieved in 95% of the MRIs, but showed various rates of 8 minor segmentation errors. The correlation between both segmentation methods was very strong (r >0.9) and the agreement very good using Bland-Altman analyses. The ventricular volumes differed significantly between semiautomated and fully automated segmentations and between preoperative and postoperative MRI. The fully automated method systematically overestimated the ventricles by a median 15 mL preoperatively and 14 mL postoperatively; hence, the magnitudes of volume changes were equivalent. Routine radiologic reports of ventricular size changes were inaccurate in 51% and lacked association with treatment response. Objectively measured ventricular volume changes correlated moderately with postoperative clinical improvement. CONCLUSIONS: A fully automated volumetric method permits reliable evaluation of preoperative ventriculomegaly and postoperative ventricular volume change in idiopathic normal pressure hydrocephalus.

Normal pressure hydrocephalus, or Hakim syndrome: review and update.

This review makes the case that idiopathic normal pressure hydrocephalus (iNPH) is an outdated term because new information indicates that the syndrome is less idiopathic and that the cerebrospinal fluid (CSF) pressure of normal individuals is affected by several factors such as body mass index, age, and sex. Our review updates the epidemiology of iNPH and provides a clinical approach to the management of these patients. All the clinical features of iNPH are common in older individuals, and each has many causes, so the diagnosis is difficult. The first step in reaching an accurate diagnosis is to address the possible contributory factors to the gait abnormality and determine what if any role iNPH may be playing. The two best diagnostic tests are neuroimaging and cerebrospinal fluid (CSF) diversion (large volume lumbar puncture or external lumbar drainage) with pre/post gait evaluation. This review provides an update on the growing evidence that vascular disease, impaired CSF absorption, congenital, and genetic factors all contribute to the pathogenesis of iNPH. We suggest replacing the term iNPH with the term Hakim syndrome (HS) in acknowledgement of the first person to describe this syndrome. Lastly, we discuss the improvements in shunt technology and surgical techniques that have decreased the risks and long-term complications of shunt surgery.

Relationship between disproportionately enlarged subarachnoid-space hydrocephalus and white matter tract integrity in normal pressure hydrocephalus.

Normal pressure hydrocephalus (NPH) patients had altered white matter tract integrities on diffusion tensor imaging (DTI). Previous studies suggested disproportionately enlarged subarachnoid space hydrocephalus (DESH) as a prognostic sign of NPH. We examined DTI indices in NPH subgroups by DESH severity and clinical symptoms. This retrospective case-control study included 33 NPH patients and 33 age-, sex-, and education-matched controls. The NPH grading scales (0-12) were used to rate neurological symptoms. Patients with NPH were categorized into two subgroups, high-DESH and low-DESH groups, by the average value of the DESH scale. DTI indices, including fractional anisotropy, were compared across 14 regions of interest (ROIs). The high-DESH group had increased axial diffusivity in the lateral side of corona radiata (1.43 ± 0.25 vs. 1.72 ± 0.25, p = 0.04), and showed decreased fractional anisotropy and increased mean, and radial diffusivity in the anterior and lateral sides of corona radiata and the periventricular white matter surrounding the anterior horn of lateral ventricle. In patients with a high NPH grading scale, fractional anisotropy in the white matter surrounding the anterior horn of the lateral ventricle was significantly reduced (0.36 ± 0.08 vs. 0.26 ± 0.06, p = 0.03). These data show that DESH may be a biomarker for DTI-detected microstructural alterations and clinical symptom severity.

Idiopathic Normal Pressure Hydrocephalus: The Real Social and Economic Burden of a Possibly Enormous Underdiagnosis Problem.

Normal Pressure Hydrocephalus (iNPH) typically affects the elderly and can cause cognitive decline, resulting in its differential diagnosis with other neurodegenerative conditions. Moreover, it is probably underdiagnosed; such under- and misdiagnosis prevents the patient from receiving the right treatment and significantly affects the quality of life and life expectancy. This investigation is an in-depth analysis of the actual incidence of iNPH in the population of the province served by our hospital (circa 580,000 individuals). The first phase of this study was conducted by visualizing a total of 1232 brain CT scans performed in the Emergency Departments of the four hospitals of our network on patients who were admitted for different complaints yet screened as suspicious for iNPH. Subsequently, corresponding Emergency Department medical records were investigated to understand the medical history of each patient in search of elements attributable to an alteration of CSF dynamics. The cohort of positive CT scans, according to the radiological and clinical inclusion criteria, included 192 patients. Among the reasons to require acute medical care, "Fall" was the most common. The cumulative incidence of CT scans suggestive of iNPH among the patients undergoing CT scans was as high as 15.58%, and the period prevalence calculated for the total amount of patients accessing the Emergency Departments was 1.084%. The real incidence of iNPH in the population may be underestimated, and the social burden linked to the assistance of patients suffering from such untreated conditions could be significantly relieved.

The metabolic spatial covariance pattern of definite idiopathic normal pressure hydrocephalus: an FDG PET study with principal components analysis.

Identification of patients with idiopathic normal pressure hydrocephalus (iNPH) in a collective with suspected neurodegenerative disease is essential. This study aimed to determine the metabolic spatial covariance pattern of iNPH on FDG PET using an established technique based on scaled subprofile model principal components analysis (SSM-PCA).We identified 11 patients with definite iNPH. By applying SSM-PCA to the FDG PET data, they were compared to 48 age-matched healthy controls to determine the whole-brain voxel-wise metabolic spatial covariance pattern of definite iNPH (iNPH-related pattern, iNPHRP). The iNPHRP score was compared between groups of patients with definite iNPH, possible iNPH (N = 34), Alzheimer's (AD, N = 38), and Parkinson's disease (PD, N = 35) applying pairwise Mann-Whitney U tests and correction for multiple comparisons.SSM-PCA of FDG PET revealed an iNPHRP that is characterized by relative negative voxel weights at the vicinity of the lateral ventricles and relative positive weights in the paracentral midline region. The iNPHRP scores of patients with definite iNPH were substantially higher than in patients with AD and PD (both p < 0.05) and non-significantly higher than those of patients with possible iNPH. Subject scores of the iNPHRP discriminated definite iNPH from AD and PD with 96% and 100% accuracy and possible iNPH from AD and PD with 83% and 86% accuracy.We defined a novel metabolic spatial covariance pattern of iNPH that might facilitate the differential diagnosis of iNPH versus other neurodegenerative disorders. The knowledge of iNPH-associated alterations in the cerebral glucose metabolism is of high relevance as iNPH constitutes an important differential diagnosis to dementia and movement disorders.

Brain blood flow pulse analysis may help to recognize individuals who suffer from hydrocephalus.

BACKGROUND: Normal pressure hydrocephalus (NPH) is often associated with altered cerebral blood flow. Recent research with the use of the ultrasonic method suggests specific changes in the shape of cardiac-related cerebral arterial blood volume (CaBV) pulses in NPH patients. Our study aims to provide a quantitative analysis of the shape of CaBV pulses, estimated based on transcranial Doppler ultrasonography (TCD) in NPH patients and healthy individuals. METHODS: The CaBV pulses were estimated using TCD cerebral blood flow velocity signals recorded from probable NPH adults and age-matched healthy individuals at rest. The shape of the CaBV pulses was compared to a triangular shape with 27 similarity parameters calculated for every reliable CaBV pulse and compared between patients and volunteers. The diagnostic accuracy of the most prominent parameter for NPH classification was evaluated using the area under the receiver operating characteristic curve (AUC). RESULTS: The similarity parameters were calculated for 31 probable NPH patients (age: 59 years (IQR: 47, 67 years), 14 females) and 23 healthy volunteers (age: 54 years (IQR: 43, 61 years), 18 females). Eighteen of 27 parameters were different between healthy individuals and NPH patients (p < 0.05). The most prominent differences were found for the ascending slope of the CaBV pulse with the AUC equal to 0.87 (95% confidence interval: 0.77, 0.97, p < 0.001). CONCLUSIONS: The findings suggest that in NPH, the ascending slope of the CaBV pulse had a slower rise, was more like a straight line, and generally was less convex than in volunteers. Prospective research is required to verify the clinical utility of these findings.