A systematic review on the epidemiology of normal pressure hydrocephalus

Fundoscopy as a diagnostic biomarker in idiopathic normal pressure hydrocephalus: a pilot study

Background

Idiopathic normal pressure hydrocephalus (iNPH) has a prevalence of approximately 5%. It is characterised by Hakim's triad of impaired gait, cognitive dysfunction and urinary incontinence. Despite radiological markers and liquor-dynamic tests, iNPH is difficult to diagnose due to many overlapping symptoms. The aim of this study was to evaluate funduscopy as a noninvasive method of screening patients with suspected iNPH.

Methods

Patients with suspected iNPH who underwent a lumbar infusion test (LIT) were included. Funduscopy was performed before the start of the LIT, and intracranial pressure (ICP) was continually measured via lumbar cannulation. Retinal images were analysed using an artificial intelligence algorithm to determine the arteriole-venule (A/V) ratio. The A/V ratio and ICP measurements were compared with the iNPH diagnosis. In addition, the mean difference in shunt response was evaluated.

Results

A significantly lower mean A/V ratio was found in the iNPH group compared with the non-iNPH group (p value: 0.02). Receiver operating characteristic curve analysis with an area under the curve of 0.75 showed a sensitivity of 88% and a specificity of 50% with an A/V cut-off of 0.86. Although not statistically significant, the mean A/V ratio was lower in the group with clinical shunt effect compared with those without (p value: 0.305).

Conclusions

This study found a statistically significant difference in baseline A/V ratios between iNPH and non-iNPH groups. This pilot study suggests the A/V ratio might be able to serve as a screening tool for iNPH. If so, this would be highly beneficial for patients and could have significant medical and socioeconomic implications.

What is idiopathic in normal pressure hydrocephalus?

INTRODUCTION

Normal pressure hydrocephalus (NPH) can be caused by acquired events - e.g. subarachnoid hemorrhage, meningitis, or trauma - or can be "idiopathic" (iNPH) when no clear cause is identifiable. The entity and nosology of iNPH has received renewed attention and has recently gone through scrutiny and academic debate.

EVIDENCE ACQUISITION

Authors searched PubMed using the following keywords: "adult hydrocephalus," "alfa synuclein," "Alzheimer's disease," "beta-amyloid," "cerebrospinal fluid," "cilia," "CSF," "genes," "hydrocephalus," "idiopathic," "Lewy Body Dementia," "phosphorylated tau," "shunt responsiveness".

EVIDENCE SYNTHESIS

During the past decades several studies have reshaped our view of iNPH, examples are the identification of monogenic forms of iNPH caused by genes involved in the structure and function of cilia or the discovery of the glymphatic system. This review will discuss the causes of iNPH and particularly the relationship with neurodegeneration in terms of: 1) coincidental association; 2) iNPH predisposing to neurodegeneration, 3. neurodegeneration predisposing to iNPH, and 4. independent processes (genetic and environmental) predisposing to both. Based on the gathered evidence, a unified model is then presented, characterized by three sequential events: impairment of CSF dynamic, occurrence of reversible signs, occurrence of irreversible signs.

CONCLUSIONS

Almost 70 years after its description, a growing literature on its basic mechanisms is clarifying that iNPH is a syndrome with pathogenetic mechanisms arising from different causes. The paradigm shift has been recognizing that iNPH is not just a CSF disorder but rather a brain disorder expressing with ventriculomegaly. Finally, the better understanding of what causes iNPH support the proposal of changing its name into "Hakim's disease."

Is normal pressure hydrocephalus a movement disorder?

Idiopathic normal pressure hydrocephalus (iNPH) represents a nosographic entity characterized by phenotypic variability. In this context, the need arises to differentiate iNPH from neurological conditions characterized by impairment in mobility and cognition, including atypical and secondary parkinsonism, with which it shares several common aspects. In this review we will discuss clinical evidence supporting different iNPH clinical phenotypes mimicking Parkinson's disease and secondary/atypical parkinsonism, indicating iNPH as a neurological condition that should be considered by movement disorders specialists. We will also propose a preliminary diagnostic algorithm combining clinical, imaging and biological markers leading to a multidimensional diagnosis of iNPH associated with parkinsonism.

Idiopathic normal pressure hydrocephalus: A critical analysis of its underrepresentation across Italian medical-scientific societies in the last 5 years

BACKGROUND

The scientific debate concerning clinical, translational and surgical aspects of iNPH could still be limited in respect to the incidence of this condition. The aim of this paper is to systematically assess the extent of the debate on INPH in the context of the congresses of the relevant medical and scientific societies in our Country.

METHODS

We thoroughly examined the websites and scientific programs of 12 leading scientific societies linked to medical specialities involved in diagnosis and management of INPH, among which the neurological, neurosurgical, neurophysiological, rehabilitation medicine and urologic societies. The amount of time (in hours) was examined in a time span of events which took place between 2019 and 2023.

RESULTS

Notably, across 4 years (2019-2023), a total of 7 out of 12 (58.3%) of the aforementioned leading scientific societies dedicated a total of zero minutes to the topic "iNPH", two further societies hosted talks for a total of less than one hours concerning such condition. The amount of time dedicated to giant intracranial aneurysms and vestibular schwannomas was in respect to the incidence of the conditions, significantly longer than the time spent debating on iNPH.

CONCLUSIONS

The results demonstrates that in our country, despite the high and increasing incidence of INPH, the awareness raised on the topic could still be limited, especially compared to other, significantly rarer intracranial conditions such as giant intracranial aneurysms and vestibular schwannomas.

Deep learning assisted quantitative analysis of Aβ and microglia in patients with idiopathic normal pressure hydrocephalus in relation to cognitive outcome

Neuropathologic changes of Alzheimer disease (AD) including Aβ accumulation and neuroinflammation are frequently observed in the cerebral cortex of patients with idiopathic normal pressure hydrocephalus (iNPH). We created an automated analysis platform to quantify Aβ load and reactive microglia in the vicinity of Aβ plaques and to evaluate their association with cognitive outcome in cortical biopsies of patients with iNPH obtained at the time of shunting. Aiforia Create deep learning software was used on whole slide images of Iba1/4G8 double immunostained frontal cortical biopsies of 120 shunted iNPH patients to identify Iba1-positive microglia somas and Aβ areas, respectively. Dementia, AD clinical syndrome (ACS), and Clinical Dementia Rating Global score (CDR-GS) were evaluated retrospectively after a median follow-up of 4.4 years. Deep learning artificial intelligence yielded excellent (>95%) precision for tissue, Aβ, and microglia somas. Using an age-adjusted model, higher Aβ coverage predicted the development of dementia, the diagnosis of ACS, and more severe memory impairment by CDR-GS whereas measured microglial densities and Aβ-related microglia did not correlate with cognitive outcome in these patients. Therefore, cognitive outcome seems to be hampered by higher Aβ coverage in cortical biopsies in shunted iNPH patients but is not correlated with densities of surrounding microglia.

Neurologic Quality of Life Outcomes in Patients with Normal Pressure Hydrocephalus After Ventriculoperitoneal Shunt Placement: A Prospective Assessment of Cognition, Mobility, and Social Participation

BACKGROUND

Idiopathic normal pressure hydrocephalus (iNPH) typically presents with gait disturbances, cognitive decline, and urinary incontinence. Symptomatic improvement generally occurs following shunt placement, but limited evidence exists on the quality of life (QOL) metrics in iNPH. Therefore, we conducted a prospective study of the effect of shunt placement on QOL in iNPH patients, using Quality of Life in Neurologic Disorders (Neuro-QOL) metrics.

METHODS

Eligible patients underwent shunt placement after evidence of symptomatic improvement following temporary cerebrospinal fluid diversion via inpatient lumbar drain trial. Patients were administered short- and long-form Neuro-QOL assessments prior to shunt placement and at 6-month and 1-year postoperative timepoints to evaluate lower extremity mobility, cognitive function, and social roles and activities participation. Changes in QOL measures were analyzed using a repeated-measures linear mixed effects model.

RESULTS

There were 48 patients with a mean age of 75.4 ± 6.3 years. Average short-form mobility scores improved by 3.9 points (14.6%) at 6-month follow-up and by 6.2 points (23.2%) at 1-year follow-up compared with preoperative baseline (P = 0.027 and P = 0.0002, respectively). Short-form cognition scores increased by 5.2 points (22.4%) at 6 months and 10.9 points (47.0%) at 1 year postoperatively (P = 0.007 and P < 0.0001, respectively). On long-form assessment, social roles and activity participation scores improved by 29.3 points (23.4%) at 6 months and 31.6 points (25.2%) at 1 year after surgery compared to baseline (P = 0.028 and P = 0.02, respectively).

CONCLUSIONS

Our findings demonstrate that shunt placement leads to improved QOL in iNPH patients across multiple domains. Significant improvements in mobility, cognition, and social roles and activity participation are realized within the first 6 months and are sustained on 1-year follow-up.

In Vivo Prevalence of Beta-Amyloid Pathology and Alzheimer's Disease Co-Pathology in Idiopathic Normal-Pressure Hydrocephalus-Association with Neuropsychological Features

Idiopathic normal-pressure hydrocephalus (iNPH) is a clinic-radiological neurological syndrome presenting with cognitive deficits, gait disturbances and urinary incontinence. It often coexists with Alzheimer's disease (AD). Due to the reversible nature of iNPH when promptly treated, a lot of studies have focused on possible biomarkers, among which are cerebrospinal fluid (CSF) biomarkers. The aim of the present study was to determine the rate of beta-amyloid pathology and AD co-pathology by measuring AD CSF biomarkers, namely, amyloid beta with 42 and 40 amino acids (Aβ42), the Aβ42/Aβ40 ratio, total Tau protein (t-Tau) and phosphorylated Tau protein at threonine 181 (p-Tau), in a cohort of iNPH patients, as well as to investigate the possible associations among CSF biomarkers and iNPH neuropsychological profiles. Fifty-three patients with iNPH were included in the present study. CSF Aβ42, Aβ40, t-Tau and p-Tau were measured in duplicate with double-sandwich ELISA assays. The neuropsychological evaluation consisted of the Mini-Mental State Examination, Frontal Assessment Battery, Five-Word Test and CLOX drawing tests 1 and 2. After statistical analysis, we found that amyloid pathology and AD co-pathology are rather common in iNPH patients and that higher values of t-Tau and p-Tau CSF levels, as well as the existence of the AD CSF profile, are associated with more severe memory impairment in the study patients. In conclusion, our study has confirmed that amyloid pathology and AD-co-pathology are rather common in iNPH patients and that CSF markers of AD pathology and t-Tau are associated with a worse memory decline in these patients.

Shunting for idiopathic normal pressure hydrocephalus

BACKGROUND

Normal pressure hydrocephalus (NPH) occurs when the brain ventricles expand, causing a triad of gait, cognitive, and urinary impairment. It can occur after a clear brain injury such as trauma, but can also occur without a clear cause (termed idiopathic, or iNPH). Non-randomised studies have shown a benefit from surgically diverting ventricular fluid to an area of lower pressure by cerebrospinal fluid (CSF)-shunting in iNPH, but historically there have been limited randomised controlled trial (RCT) data to confirm this.

OBJECTIVES

To determine the effect of CSF-shunting versus no CSF-shunting in people with iNPH and the frequency of adverse effects of CSF-shunting in iNPH.

SEARCH METHODS

We searched the Cochrane Dementia and Cognitive Improvement Group's register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid SP), Embase (Ovid SP), PsycINFO (Ovid SP), CINAHL (EBSCOhost), Web of Science Core Collection (Clarivate), LILACS (BIREME), ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform on 15 February 2023.

SELECTION CRITERIA

We included only RCTs of people who had symptoms of gait, cognitive, or urinary impairment with communicating hydrocephalus (Evans index of > 0.3) and normal CSF pressure. Control groups included those with no CSF shunts or those with CSF shunts that were in 'inactive' mode.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. Where necessary, we contacted study authors requesting data not provided in the papers. We assessed the overall certainty of the evidence using GRADE.

MAIN RESULTS

We included four RCTs, of which three were combined in a meta-analysis. The four RCTs included 140 participants (73 with immediate CSF-shunting and 67 controls who had delayed CSF-shunting) with an average age of 75 years. Risk of bias was low in all parallel-group outcomes evaluated apart from gait speed, cognitive function (general cognition and Symbol Digit Test) (some concerns) and adverse events, which were not blind-assessed. CSF-shunting probably improves gait speed at less than six months post-surgery (standardised mean difference (SMD) 0.62, 95% confidence interval (CI) 0.24 to 0.99; 3 studies, 116 participants; moderate-certainty evidence). CSF-shunting may improve qualitative gait function at less than six months post-surgery by an uncertain amount (1 study, 88 participants; low-certainty evidence). CSF-shunting probably results in a large reduction of disability at less than six months post-surgery (risk ratio 2.08, 95% CI 1.31 to 3.31; 3 studies, 118 participants; moderate-certainty evidence). The evidence is very uncertain about the effect of CSF-shunting on cognitive function at less than six months post-CSF-shunt surgery (SMD 0.35, 95% CI -0.04 to 0.74; 2 studies, 104 participants; very low-certainty evidence). The evidence is also very uncertain about the effect of CSF-shunt surgery on adverse events (1 study, 88 participants; very low-certainty evidence). There were no data regarding the effect of CSF-shunting on quality of life.

AUTHORS' CONCLUSIONS

We found moderate-certainty evidence that CSF-shunting likely improves gait speed and disability in iNPH in the relative short term. The evidence is very uncertain regarding cognition and adverse events. There were no longer-term RCT data for any of our prespecified outcomes. More studies are required to improve the certainty of these findings. In addition, more information is required regarding patient ethnicity and the effect of CSF-shunting on quality of life.

An Interdisciplinary Protocol for Ventriculoperitoneal Shunt Patient Selection in Normal Pressure Hydrocephalus

BACKGROUND

Normal pressure hydrocephalus can be treated with ventriculoperitoneal shunt (VPS) placement, but no broadly implemented indication for VPS exists.

METHODS

Our protocol consists of physical therapy and occupational therapy practitioners administering validated tests of gait, balance, and cognition before and after lumbar drain placement. Specific tests include: Timed "Up & Go", Tinetti Gait and Balance Assessment, Berg Balance Scale, Mini Mental Status Exam, Trail Making Test Part B, and the Rey Auditory and Visual Learning Test. Minimal clinically important difference values for each test were determined from literature review. A retrospective review of patients treated under this protocol was performed. The primary outcomes were candidacy for VPS based on the protocol and patient-reported symptomatic improvement after VPS placement.

RESULTS

A total of 48/75 (64%) patients received VPS. A total of 43/48 (89.6%) of those shunted reported improved symptoms at 6-week follow-up. However, 10/22 (45.5%) reported worsening symptoms at 1-year follow-up. The mean Tinetti score significantly increased after lumbar drain in patients who improved with VPS compared to the no shunt group (4.27 vs. -0.48, P < 0.001). A total of 6/33 (18%) patients with postoperative imaging had a subdural fluid collection identified and 3/49 (6%) had other complications, including 1 seizure, 1 intracerebral hemorrhage, and 1 stroke.

CONCLUSIONS

Standardized assessment of gait, balance, and cognition before and after temporary cerebrospinal fluid diversion identifies patients with normal pressure hydrocephalus likely to benefit from VPS placement with a low complication rate. One year after VPS, approximately one half of patients had symptoms recurrence.

Comparison of decline in different cognitive domain in patients with normal pressure hydrocephalus

We sought to describe the cognitive profile of patients with Idiopathic Normal Pressure Hydrocephalus (iNPH) using a comprehensive neuropsychological battery. Based on age and education correlated norms, we aimed to compare performance in each measured cognitive domain: executive functions (EFs), verbal memory (VM), non-verbal memory (nVM), visuoconstructional abilities (VA) and attention/psychomotor speed (A/PS). Patients diagnosed with iNPH underwent comprehensive neuropsychological evaluation before shunting. Their performance was compared to the age and education correlated norms. Correlation of different cognitive domains in iNPH profile was performed. A total of 53 iNPH patients (73.21 ± 5.48 years) were included in the study. All of the measured cognitive domains were significantly damaged. The most affected domains were EFs and VM (p<0.001 and p<0.001, respectively). A/PS domain was affected milder than EFs and VM (p<0.001). The least affected domains were nVM (p<0.001) and VA (p<0.001). Patients with iNPH are affected in all cognitive domains and the cognitive decline is uneven across these domains. The impairment of memory was shown to depend on the presented material. VM was shown to be much more severely affected than nVM and along with VM, EFs were shown to be the most affected. A/PS speed was shown to be less affected than VM and EFs and the least affected domains were nVM and VA.

Application of LRG mechanism in normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) is a prevalent type of hydrocephalus, including secondary normal pressure hydrocephalus (SNPH) and idiopathic normal pressure hydrocephalus (INPH). However, its clinical diagnosis and pathological mechanism are still unclear. Leucine-rich α-2 glycoprotein (LRG) is involved in various human diseases, including cancer, diabetes, cardiovascular disease, and nervous system diseases. Now the physiological mechanism of LRG is still being explored. According to the current research results on LRG, we found that the agency of LRG has much to do with the known pathological process of NPH. This review focuses on analyzing the LRG signaling pathways and the pathological mechanism of NPH. According to the collected literature evidence, we speculated that LRG probably be involved in the pathological process of NPH. Finally, based on the mechanism of LRG and NPH, we also summarized the evidence of molecular targeted therapies for future research and clinical application.

The Causal Effect of Gut Microbiota on the Development of Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

Older people are particularly at risk for idiopathic normal pressure hydrocephalus (iNPH), a rare neurological condition without known risk factors. Several recent observational studies have reported that gut microbiota composition is associated with iNPH. However, the causal impact of gut microbiota on iNPH is unknown.

METHODS

Single nucleotide polymorphisms strongly associated with 196 gut microbiota (18,340 individuals) were selected as instrumental factors, and the results were iNPH data (322 cases of iNPH and 21,043 controls). Random effects, inverse variance weighting, weighted medians, and Mendelian random (MR) -Egger were used to investigate causal effects. The Cochran's Q test, funnel plot, leave-one-out analysis, MR-Egger intercept test, and outlier (Global) test were employed in the sensitivity analysis to identify and compensate for the presence of pleiotropy. The MR-Steiger test also examined the hypothesised connection between exposure and result.

RESULTS

Our findings are mainly based on the inverse variance weighting approach and support a causal relationship between 6 gut microbial taxa and iNPH. We observed an inverse association between the Eubacterium fissicatena group (P = 0.007) and Lactococcus (P = 0.038) and iNPH, whereas Adlercreutzia (P = 0.029), Dialister (P = 0.040), Romboutsia (P = 0.027), Sutterella (P = 0.019) may be associated with an increased risk of iNPH. The results of the sensitivity analysis were robust.

CONCLUSIONS

Our findings suggest that certain gut bacteria may enhance iNPH risk. Research is required to determine whether the societal impact of iNPH is lessened in older people by sensible control of their gut microbiota.

Alzheimer's Disease CSF Biomarkers as Possible Indicators of Tap-Test Response in Idiopathic Normal Pressure Hydrocephalus

The aim of the present study is the evaluation of established Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers in patients with idiopathic normal-pressure hydrocephalus (iNPH), both individually and as a total profile, and the investigation of their use as potential predictors of Tap-test responsiveness. Fifty-three patients with iNPH participated in the study. Aβ42, Aβ40, total Tau and phospho-Tau proteins were measured in duplicate with double-sandwich ELISA assays. Clinical evaluation involved a 10 m timed walk test before an evacuative lumbar puncture (LP) and every 24 h for three consecutive days afterwards. Neuropsychological assessment involved a mini-mental state examination, frontal assessment battery, 5-word test and CLOX drawing test 1 and 2, which were also performed before and 48 h after LP. Response in the Tap-test was defined as a 20% improvement in gait and/or a 10% improvement in neuropsychological tests. The Aβ42/Aβ40 ratio was found to be significantly higher in Tap-test responders than non-responders. Total Tau and phospho-Tau CSF levels also differed significantly between these two groups, with Tap-test responders presenting with lower levels compared to non-responders. Regarding the AD CSF biomarker profile (decreased amyloid and increased Tau proteins levels), patients with a non-AD profile were more likely to have a positive response in the Tap-test than patients with an AD profile.

Managing Idiopathic Normal Pressure Hydrocephalus: Need for a Change of Mindset

Idiopathic normal pressure hydrocephalus (iNPH) refers to a complex brain disorder characterized by ventricular enlargement and the classic Hakim's triad of gait and balance difficulties, urinary incontinence, and cognitive impairment. It predominantly affects older patients in the absence of an identified cause. As the elderly population continues to increase, iNPH becomes a growing concern in the complex spectrum of neuro-geriatric care, with significant socio-economic implications. However, unlike other well-structured management approaches for neurodegenerative disorders, the management of iNPH remains largely uncodified, leading to suboptimal care in many cases. In this article, we highlighted the challenges of current practice and identify key points for an optimal structuration of care for iNPH. Adopting a global approach to iNPH could facilitate a progressive shift in mindset, moving away from solely aiming to cure an isolated neurological disease with uncertain outcomes to providing comprehensive care that focuses on improving the daily life of frail patients with complex neurodegenerative burdens, using tailored goals.

Imaging Markers for Normal Pressure Hydrocephalus: An Overview

Idiopathic bormal pressure hydrocephalus (iNPH) is a neurological syndrome that clinically presents with Hakim's triad, namely cognitive impairment, gait disturbances, and urinary incontinence. The fact that iNPH is potentially reversible makes its accurate and early diagnosis of paramount importance. Its main imaging characteristic is the dilation of the brain's ventricular system and the imaging parameters are also included in its diagnostic criteria along with clinical data. There is a variety of different modalities used and a great number of imaging markers that have been described while assessing iNPH patients. The present literature review attempts to describe the most important of these imaging markers and to shed some light on their role in diagnosis, differential diagnosis, and possibly prognosis of this potentially reversible neurological syndrome.

Hydrocephalus: A neuropsychological and theoretical primer

Hydrocephalus is a common neurological condition, the hallmark feature of which is an excess in production, or accumulation, of cerebrospinal fluid in the ventricles. Although it is associated with diffuse damage to paraventricular brain areas, patients are broadly typified by a particular pattern of cognitive impairments that include deficits in working memory, attention, and spatial abilities. There have, however, been relatively few neuropsychological accounts of the condition. Moreover, theories of the relationship between aetiology and impairment appear to have emerged in isolation of each other, and proffer fundamentally different accounts. In this primer, we aim to provide a comprehensive and contemporary overview of hydrocephalus for the neuropsychologist, covering cognitive sequelae and theoretical interpretations of their origins. We review clinical and neuropsychological assays of cognitive profiles, along with the few studies that have addressed more integrative behaviours. In particular, we explore the distinction between congenital or early-onset hydrocephalus with a normal-pressure variant that can be acquired later in life. The relationship between these two populations is a singularly interesting one in neuropsychology since it can allow for the examination of typical and atypical developmental trajectories, and their interaction with chronic and acute impairment, within the same broad neurological condition. We reflect on the ramifications of this for our subject and suggest avenues for future research.

Association between vascular risk factors and idiopathic normal pressure hydrocephalus: a Mendelian randomization study

BACKGROUND AND OBJECTIVE

Patients with idiopathic normal pressure hydrocephalus (iNPH) have a higher prevalence of hypertension and diabetes. However, the causal effects of these vascular risk factors on iNPH remain unclear. This study aimed to explore the causal relationship between vascular risk factors (VRFs) and iNPH.

METHODS

We conducted the Mendelian randomization (MR) analysis of iNPH. We included nineteen vascular risk factors related to hypertension, diabetes, lipids, obesity, smoking, alcohol consumption, exercise, sleep, and cardiovascular events as exposure factors. We used the inverse-variance weighted method for causal effect estimation and weighted median, maximum likelihood, and MR Egger regression methods for sensitivity analyses.

RESULTS

We found that genetically predicting essential hypertension (OR = 1.608 (1.330-1.944), p = 0.013) and increased sleep duration (OR = 16.395 (5.624-47.799), p = 0.009) were associated with higher odds of iNPH. Type 1 diabetes (OR = 0.869 (0.828-0.913), p = 0.004) was associated with lower odds of iNPH. For the other 16 VRFs, there was no evidence that they were significantly associated with iNPH. Sensitivity analyses showed that essential hypertension and type 1 diabetes were significantly associated with iNPH.

CONCLUSION

In our MR study on VRFs and iNPH, we found essential hypertension to be a causal risk factor for iNPH. This suggests that hypertension may be involved in the pathophysiological mechanism of iNPH.

TRPV4 mRNA is elevated in the caudate nucleus with NPH but not in Alzheimer's disease

Symptoms of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD) are somewhat similar, and it is common to misdiagnose these two conditions. Although there are fluid markers detectable in humans with NPH and AD, determining which biomarker is optimal in representing genetic characteristics consistent throughout species is poorly understood. Here, we hypothesize that NPH can be differentiated from AD with mRNA biomarkers of unvaried proximity to telomeres. We examined human caudate nucleus tissue samples for the expression of transient receptor potential cation channel subfamily V member 4 (TRPV4) and amyloid precursor protein (APP). Using the genome data viewer, we analyzed the mutability of TRPV4 and other genes in mice, rats, and humans through matching nucleotides of six genes of interest and one house keeping gene with two factors associated with high mutation rate: 1) proximity to telomeres or 2) high adenine and thymine (A + T) content. We found that TRPV4 and microtubule associated protein tau (MAPT) mRNA were elevated in NPH. In AD, mRNA expression of TRPV4 was unaltered unlike APP and other genes. In mice, rats, and humans, the nucleotide size of TRPV4 did not vary, while in other genes, the sizes were inconsistent. Proximity to telomeres in TRPV4 was <50 Mb across species. Our analyses reveal that TRPV4 gene size and mutability are conserved across three species, suggesting that TRPV4 can be a potential link in the pathophysiology of chronic hydrocephalus in aged humans (>65 years) and laboratory rodents at comparable ages.

Gait, falls, cognitive function, and health-related quality of life after shunt-treated idiopathic normal pressure hydrocephalus-a single-center study

BACKGROUND

Normal pressure hydrocephalus (NPH) is a neurological disorder, characterized by gait- and balance disturbance, cognitive deterioration, and urinary incontinence, combined with ventricular enlargement. Gait ability, falls, cognitive status, and health-related quality of life pre and post surgery have not previously been studied at Karolinska University Hospital.

METHODS

One hundred and eighteen patients with iNPH that underwent shunt surgery at Karolinska University Hospital during the years from 2016 to 2018 were included. Results of walking tests, test for cognitive function, and self-estimated health-related quality of life, before and 3 months after surgery, were collected retrospectively as a single-center study.

RESULTS

Walking ability, cognitive function, and health-related quality of life significantly increased 3 months after shunt surgery. A positive significant correlation was seen between a higher self-estimated quality of life and walking ability.

CONCLUSIONS

Patients with suspected iNPH treated with shunt surgery at Karolinska University Hospital improved their walking ability and cognitive functioning 3 months after shunt surgery. A positive significant correlation was seen between a higher self-estimated quality of life and walking ability but not with increased cognitive function. We then concluded that the selection of patients for shunting maintained a high standard.

Callosal Angle Sub-Score of the Radscale in Patients with Idiopathic Normal Pressure Hydrocephalus Is Associated with Positive Tap Test Response

The aim of the present study was the implementation of the composite imaging “Radscale” in patients with idiopathic normal pressure hydrocephalus (iNPH) and the evaluation of its score, as well as absolute stroke volume and peak flow velocity of cerebrospinal fluid (CSF) in aqueduct as indicators of a positive response following a tap test. Forty-five patients with iNPH were included. Clinical evaluation involved the 10 m timed walk test before and every 24 h for 3 consecutive days after evacuative lumbar puncture (LP). Neuropsychological evaluation comprised a mini mental state examination (MMSE), frontal assessment battery (FAB), 5-word test (5WT) and CLOX drawing test 1 and 2, which were carried out before and 48 h after LP. The tap test’s response was defined as a ≥20% improvement in gait and/or a ≥10% improvement in neuropsychological tests. All scores of neuropsychological and clinical variables, except for immediate 5WT and CLOX-1, differed significantly before and 48 h after LP. Improvement in time and steps of a 10 m timed walk test differed significantly between female and male patients. Out of 45 total patients, 19 were tap test responders and 26 non-responders. The total score of Radscale and CSF flow parameters did not differ between responders and non-responders. However, “Callosal angle” sub-score differed significantly between these two groups. A greater “callosal angle” sub-score, meaning more acute callosal angle, was associated with a positive tap test response, rendering it a useful measurement in the stratification of iNPH patients that will potentially respond to CSF shunting.

Shunting for idiopathic normal pressure hydrocephalus

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To determine the effect of cerebrospinal fluid (CSF) shunting versus no CSF shunting in people with idiopathic normal pressure hydrocephalus (iNPH).

To determine the frequency of adverse effects of CSF shunting in iNPH

Water Diffusivity Changes Along the Perivascular Space After Lumboperitoneal Shunt Surgery in Idiopathic Normal Pressure Hydrocephalus

Background

The aim of this study was to evaluate the water diffusivity changes along the perivascular space after lumboperitoneal shunt (LPS) surgery in idiopathic normal pressure hydrocephalus.

Methods

Nine patients diagnosed with idiopathic normal pressure hydrocephalus (iNPH; three men and six women, mean age ± SD = 75.22 ± 5.12 years) according to the guidelines for iNPH in Japan were included in the study. Post-LPS surgery, six patients with iNPH who exhibited improvement in symptoms were defined as responder subjects, while three patients with iNPH who did not were defined as non-responder subjects. We calculated the mean analysis along the perivascular space (ALPS) index of the left and right hemispheres and compared the differences between pre- and post-LPS surgery mean ALPS indices in iNPH patients. In the responder or non-responder subjects, the mean ALPS indices in the pre- and post-operative iNPH groups were compared using Wilcoxon signed-rank tests. Next, correlation analyses between pre- and post-operation changes in the mean ALPS index and clinical characteristics were conducted.

Results

The mean ALPS index of the post-operative iNPH group was significantly higher than that of the pre-operative iNPH group (p = 0.021). In responder subjects, the mean ALPS index of the post-operative iNPH group was significantly higher than that of the pre-operative iNPH group (p = 0.046). On the other hand, in the non-responder subjects, the mean ALPS index of the post-operative iNPH group was not significantly different compared to the pre-operative iNPH group (p = 0.285). The mean ALPS index change was not significantly correlated with changes in the Mini-Mental State Examination (MMSE) score (r = −0.218, p = 0.574), Frontal Assessment Battery (FAB) score (r = 0.185, p = 0.634), Trail Making Test A (TMTA) score (r = 0.250, p = 0.516), and Evans' index (r = 0.109, p = 0.780). In responder subjects, the mean ALPS index change was significantly correlated with Evans' index in pre-operative patients with iNPH (r = 0.841, p = 0.036).

Conclusion

This study demonstrates the improved water diffusivity along perivascular space in patients with iNPH after LPS surgery. This could be indicative of glymphatic function recovery following LPS surgery.

Application of Evans Index in Normal Pressure Hydrocephalus Patients: A Mini Review

With an ever-growing aging population, the prevalence of normal pressure hydrocephalus (NPH) is increasing. Clinical symptoms of NPH include cognitive impairment, gait disturbance, and urinary incontinence. Surgery can improve symptoms, which leads to the disease's alternative name: treatable dementia. The Evans index (EI), defined as the ratio of the maximal width of the frontal horns to the maximum inner skull diameter, is the most commonly used index to indirectly assess the condition of the ventricles in NPH patients. EI measurement is simple, fast, and does not require any special software; in clinical practice, an EI >0.3 is the criterion for ventricular enlargement. However, EI's measurement methods, threshold setting, correlation with ventricle volume, and even its clinical value has been questioned. Based on the EI, the z-EI and anteroposterior diameter of the lateral ventricle index were derived and are discussed in this review.

White Matter Microstructural Damage Associated With Gait Abnormalities in Idiopathic Normal Pressure Hydrocephalus

Background: Idiopathic normal pressure hydrocephalus (iNPH) is a common disease in elderly adults. Patients with iNPH are generally characterized by progressive gait impairment, cognitive deficits, and urinary urgency and/or incontinence. A number of radiographic studies have shown that iNPH patients have enlarged ventricles and altered brain morphology; however, few studies have focused on the relationships between altered brain structure and gait dysfunction due to iNPH. Thus, this study aimed to evaluate the abnormalities of white matter (WM) correlated with gait impairment in iNPH patients and to gain a better understanding of its underlying pathology. Methods: Fifteen iNPH patients (five women, 10 men) were enrolled in this study, and each patient's demographic and gait indices were collected. First, we performed a correlation analysis between the demographic and gait indices. Then, all gait indices were grouped according to the number of WM hyperintensities (WMH) among each WM tract (JHU WM tractography atlas), to perform comparative analysis. Results: Considering sex and illness duration as covariates, correlation analysis showed a significantly negative correlation between step length (r = -0.80, p = 0.001), pace (r = -0.84, p = 2.96e-4), and age. After removing the effects of age, sex, and illness duration, correlation analysis showed negative correlation between step length (r = -0.73, p = 0.007), pace (r = -0.74, p = 0.005), and clinical-grade score and positive correlation between 3-m round trip time (r = 0.66, p = 0.021), rising time (r = 0.76, p = 0.004), and clinical-grade score. Based on WMH of each white matter tract, gait indices showed significant differences (p < 0.05/48, corrected by Bonferroni) between fewer WMH patients and more WMH in the middle cerebellar peduncle, left medial lemniscus, left posterior limb of the internal capsule (IC), and right posterior limb of the IC. Conclusions: Our results indicated that iNPH patients exhibited gait-related WM abnormalities located in motor and sensory pathways around the ventricle, which is beneficial to understand the underlying pathology of iNPH.

The role of diffusion tensor imaging in idiopathic normal pressure hydrocephalus: A literature review

Idiopathic normal pressure hydrocephalus (iNPH) is a syndrome that comprises a triad of gait disturbance, dementia and urinary incontinence, associated with ventriculomegaly in the absence of elevated intraventricular cerebrospinal fluid (CSF) pressure. It is important to identify patients with iNPH because some of its clinical features may be reversed by the insertion of a CSF shunt. The diagnosis is based on clinical history, physical examination and brain imaging, especially magnetic resonance imaging (MRI). Recently, some papers have investigated the role of diffusion tensor imaging (DTI) in evaluating white matter alterations in patients with iNPH. DTI analysis in specific anatomical regions seems to be a promising MR biomarker of iNPH and could also be used in the differential diagnosis from other dementias. However, there is a substantial lack of structured reviews on this topic. Thus, we performed a literature search and analyzed the most recent and pivotal articles that investigated the role of DTI in iNPH in order to provide an up-to-date overview of the application of DTI in this setting. We reviewed studies published between January 2000 and June 2020. Thirty-eight studies and four reviews were included. Despite heterogeneity in analysis approaches, the majority of studies reported significant correlations between DTI and clinical symptoms in iNPH patients, as well as different DTI patterns in patients with iNPH compared to those with Alzheimer or Parkinson diseases. It remains to be determined whether DTI could predict the success after CSF shunting.

The Pathogenesis Based on the Glymphatic System, Diagnosis, and Treatment of Idiopathic Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a rare neurological disorder with no clear prevalence factors and is a significant danger to the elderly. The intracranial glymphatic system is the internal environment that maintains brain survival and metabolism, and thus fluid exchange changes in the glymphatic system under various pathological conditions can provide important insights into the pathogenesis and differential diagnosis of many neurodegenerative diseases such as iNPH. iNPH can be diagnosed using a combination of clinical symptoms, imaging findings and history, and cerebrospinal fluid biomarkers due to the glymphatic system disorder. However, only few researchers have linked the two. Shunt surgery can improve the glymphatic system disorders in iNPH patients, and the surgical approach is determined using a combination of clinical diagnosis and trials. Therefore, we have composed this review to provide a future opportunity for elucidating the pathogenesis of iNPH based on the glymphatic system, and link the glymphatic system to the diagnosis and treatment of iNPH. The review will provide new insights into the medical research of iNPH.