Evaluation of coexistence of Alzheimer's disease in idiopathic normal pressure hydrocephalus using ELISA analyses for CSF biomarkers

The impact of neurocognitive and psychiatric disorders on the risk of idiopathic normal pressure hydrocephalus: A bidirectional Mendelian randomization study

BACKGROUND

Neurocognitive and psychiatric disorders have been proved that they can comorbid more often with idiopathic normal pressure hydrocephalus (iNPH) than general population. However, the potential causal association between these disorders and iNPH has not been assessed. Thus, our study aims to investigate the causal relationship between them based on a bidirectional Mendelian randomization (MR) analysis.

METHODS

Random effects of the inverse variance weighted (IVW) method were conducted to obtain the causal association among the neurocognitive disorders, psychiatric disorders, and iNPH. Genome-wide association studies (GWAS) of 12 neurocognitive and psychiatric disorders were downloaded via the OpenGWAS database, GWAS Catalog, and Psychiatric Genomics Consortium, whereas GWAS data of iNPH were obtained from the FinnGen consortium round 9 release, with 767 cases and 375,610 controls of European ancestry. We also conducted the sensitivity analysis in these significant causal inferences using weighted median model, Cochrane's Q test, MR-Egger regression, MR Pleiotropy Residual Sum and Outlier detect and the leave-one-out analysis.

RESULTS

For most of the neurocognitive and psychiatric disorders, no causal association was established between them and iNPH. We have found that iNPH (odds ratio [OR] = 1.030, 95% confidence interval [CI]: 1.011-1.048, p = .001) is associated with increased risk for schizophrenia, which failed in validation of sensitivity analysis. Notably, genetically predicted Parkinson's disease (PD) is associated with increased risk of iNPH (OR = 1.256, 95% CI: 1.045-1.511, p = .015).

CONCLUSION

Our study has revealed the potential causal effect in which PD associated with an increased risk of iNPH. Further study is warranted to investigate the association between PD and iNPH and the potential underlying mechanism.

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.

Cerebrospinal Fluid Biomarkers in iNPH: A Narrative Review

Idiopathic normal pressure hydrocephalus (iNPH) is a neurological syndrome characterized by the clinical triad of gait disorder, cognitive impairment and urinary incontinence. It has attracted interest because of the possible reversibility of symptoms, especially with timely treatment. The main pathophysiological theory is based on a vicious circle of disruption in circulation of cerebrospinal fluid (CSF) that leads to the deceleration of its absorption. Data regarding CSF biomarkers in iNPH are contradictory and no definite CSF biomarker profile has been recognized as in Alzheimer's disease (AD), which often co-exists with iNPH. In this narrative review, we investigated the literature regarding CSF biomarkers in iNPH, both the established biomarkers total tau protein (t-tau), phosphorylated tau protein (p-tau) and amyloid peptide with 42 amino acids (Aβ42), and other molecules, which are being investigated as emerging biomarkers. The majority of studies demonstrate differences in CSF concentrations of Aβ42 and tau-proteins (t-tau and p-tau) among iNPH patients, healthy individuals and patients with AD and vascular dementia. iNPH patients present with lower CSF Aβ42 and p-tau concentrations than healthy individuals and lower t-tau and p-tau concentrations than AD patients. This could prove helpful for improving diagnosis, differential diagnosis and possibly prognosis of iNPH patients.

Cognitive Impairment in Idiopathic Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a significant cause of the severe cognitive decline in the elderly population. There is no cure for iNPH, but cognitive symptoms can be partially alleviated through cerebrospinal fluid (CSF) diversion. In the early stages of iNPH, cognitive deficits occur primarily in the executive functions and working memory supported by frontostriatal circuits. As the disease progresses, cognition declines continuously and globally, leading to poor quality of life and daily functioning. In this review, we present recent advances in understanding the neurobiological mechanisms of cognitive impairment in iNPH, focusing on (1) abnormal CSF dynamics, (2) dysfunction of frontostriatal and entorhinal-hippocampal circuits and the default mode network, (3) abnormal neuromodulation, and (4) the presence of amyloid-β and tau pathologies.

Update on the Cognitive Presentations of iNPH for Clinicians

This mini-review focuses on cognitive impairment in iNPH. This symptom is one of the characteristic triad of symptoms in a condition long considered to be the only treatable dementia. We present an update on recent developments in clinical, neuropsychological, neuroimaging and biomarker aspects. Significant advances in our understanding have been made, notably regarding biomarkers, but iNPH remains a difficult diagnosis. Stronger evidence for permanent surgical treatment is emerging but selection for treatment remains challenging, particularly with regards to cognitive presentations. Encouragingly, there has been increasing interest in iNPH, but more research is required to better define the underlying pathology and delineate it from overlapping conditions, in order to inform best practise for the clinician managing the cognitively impaired patient. In the meantime, we strongly encourage a multidisciplinary approach and a structured service pathway to maximise patient benefit.

Alzheimer’s Disease CSF Biomarker Profiles in Idiopathic Normal Pressure Hydrocephalus

Patients with idiopathic normal pressure hydrocephalus (iNPH) frequently show pathologic CSF Aβ₄₂ levels, comparable with Alzheimer’s Disease (AD). Nevertheless, the clinical meaning of these findings has not been fully explained. We aimed to assess the role of AD CSF biomarkers (Aβ₄₂, Aβ₄₂/Aβ₄₀, p-tau, t-tau) in iNPH. To this purpose, we enrolled 44 patients diagnosed with iNPH and 101 with AD. All the patients underwent CSF sampling. We compared CSF biomarker levels in iNPH and AD: Aβ₄₂ levels were not different between iNPH and AD, while Aβ₄₂/Aβ₄₀, p-tau, and t-tau were significantly different and showed excellent accuracy in distinguishing iNPH and AD. A multiple logistic regression analysis showed that Aβ₄₂/Aβ₄₀ was the variable that most contributed to differentiating the two groups. Furthermore, iNPH patients with positive Aβ₄₂/Aβ₄₀ had higher p-tau and t-tau than iNPH patients with negative Aβ₄₂/Aβ₄₀. Those iNPH patients who showed cognitive impairment had lower Aβ₄₂/Aβ₄₀ and higher p-tau than patients without cognitive impairment. We concluded that positive CSF Aβ₄₂ with negative Aβ₄₂/Aβ₄₀, p-tau, and t-tau is a typical CSF profile of iNPH. On the contrary, positive Aβ₄₂/Aβ₄₀ in iNPH patients, especially when associated with positive p-tau, may lead to suspicion of a coexistent AD pathology.

Higher levels of neurofilament light chain and total tau in CSF are associated with negative outcome after shunt surgery in patients with normal pressure hydrocephalus

Background

Lumbar punctures are a common examination in the work-up of patients with idiopathic normal pressure hydrocephalus (iNPH) and cerebrospinal fluid (CSF) biomarkers should therefore be available for use in selection of shunt candidates. The aim of this study was to investigate if CSF biomarkers are associated with outcome after shunt surgery alone or in combination with comorbidity and imaging markers, and investigate associations between CSF biomarkers and symptoms.

Methods

Preoperative CSF biomarkers were analyzed in 455 patients operated with shunt surgery for iNPH at a single center during 2011–2018. Symptoms before and 12 months after shunt surgery were graded with the Swedish iNPH scale. Neurofilament light chain protein (NfL), total tau (T-tau), phosphorylated tau (P-tau) and amyloid beta1-42 (Aβ1-42) CSF levels were measured. Evans’ index and disproportionately enlarged subarachnoid space hydrocephalus were measured on preoperative CT-scans. Preoperative evaluation and follow-up 12 months after shunt surgery were available in 376 patients.

Results

Higher levels of NfL and T-tau were associated with less improvement after shunt surgery (β = − 3.10, p = 0.016 and β = − 2.45, p = 0.012, respectively). Patients whose symptoms deteriorated after shunt surgery had higher preoperative levels of NfL (1250 ng/L [IQR:1020–2220] vs. 1020 [770–1649], p < 0.001) and T-tau (221 ng/L [IQR: 159–346] vs. 190 [135–261], p = 0.0039) than patients with postoperative improvement on the iNPH scale. Among the patients who improved ≥ 5 levels on the iNPH scale (55%), NfL was abnormal in 22%, T-tau in 14%, P-tau in 6% and Aβ1-42 in 45%, compared with normal reference limits. The inclusion of CSF biomarkers, imaging markers and comorbidity in multivariate predictive Orthogonal Projections to Latent Structures (OPLS) models to did not improve predictability in outcome after shunt surgery.

Conclusions

Higher levels of T-tau and NfL were associated with a less favorable response to shunt surgery, suggesting a more active neurodegeneration in this group of patients. However, CSF levels of these biomarkers can be elevated also in patients who respond to shunt surgery. Thus, none of these CSF biomarkers, alone or used in combination, are suitable for excluding patients from surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-022-00306-2.

Amyloid Positive Hydrocephalus: A Hydrocephalic Variant of Alzheimer's Disease?

BACKGROUND

Alzheimer's disease (AD) and normal pressure hydrocephalus (NPH) commonly coexist.

OBJECTIVE

We aimed to characterize an overlapping syndrome of AD and NPH that presents with gait disturbance, ventriculomegaly on magnetic resonance imaging, and significant amyloid deposition on positron emission tomography (PET).

METHODS

Of 114 patients who underwent cerebrospinal fluid (CSF) drainage for a possible diagnosis of NPH between 2015 and 2020 in Samsung Medical Center, we identified 24 patients (21.1%) with the NPH patients with amyloid deposition on PET, which we referred to as hydrocephalic AD in this study. We compared their clinical and imaging findings with those of 123 typical AD without hydrocephalic signs/symptoms. We also investigated the frequency and potential predictors of the tap test response in hydrocephalic AD.

RESULTS

Evans' index was 0.36±0.03, and a disproportionately enlarged subarachnoid space was present in 54.2% of the hydrocephalic AD patients. The mean age (75.2±7.3 years) and the APOE4 frequency (68.2%) did not differ from those of AD controls. However, the hydrocephalic AD patients showed better memory and language performance, and a thinner cingulate cortex. About 42% of the hydrocephalic AD patients responded to the tap test, of whom seven underwent shunt surgery. Cognition did not improve, whereas gait improved after shunt surgery in all.

CONCLUSION

Hydrocephalic AD has different neuropsychological and imaging characteristics from typical AD. Future studies are warranted to further investigate the effect of CSF removal on their clinical course and to elucidate the pathophysiological interaction between amyloid and NPH.

The role of amyloid PET in patient selection for extra-ventricular shunt insertion for the treatment of idiopathic normal pressure hydrocephalus: A pooled analysis

BACKGROUND

Idiopathic Normal Pressure Hydrocephalus (iNPH) can be effectively treated through shunt insertion. However, most shunted patients experience little or no clinical benefit, which suggests suboptimal patient selection. While contentious, multiple studies have reported poorer shunt outcomes associated with concomitant Alzheimer's disease. Prompted by this observation, multiple studies have assessed the role of amyloid PET, a specific test for Alzheimer's disease, in patient selection for shunting.

METHODS

A comprehensive literature search was performed to identify studies that assessed the association between amyloid PET result and the clinical response to shunting in patients with suspected iNPH. Pooled diagnostic statistics were calculated.

RESULTS

Across three relevant studies, a total of 38 patients with suspected iNPH underwent amyloid PET imaging and shunt insertion. Twenty-three patients had a positive clinical response to shunting. 18/28 (64.3%) of patients with a negative amyloid PET and 5/10 (50%) with a positive amyloid PET had a positive response to shunting. The pooled sensitivity, specificity and accuracy was 33.3%, 76.2% and 58.3%. None of these statistics reached statistical significance.

CONCLUSION

The results of this pooled analysis do not support the selection of patients with suspected iNPH for shunting on the basis of amyloid PET alone. However, due to small cohort sizes and weakness in study design, further high-quality studies are required to properly determine the role of amyloid PET in assessing this complex patient group.

Cerebrospinal Fluid Alzheimer's Biomarkers and Neurofilament Light Profile of Idiopathic Normal Pressure Hydrocephalus in China: A PUMCH Cohort Study

INTRODUCTION

Idiopathic normal pressure hydrocephalus (iNPH) is one of the potentially reversible dementias. Early and accurate diagnosis is important for patients' prognosis. Emerging evidence shows fluid biomarkers are useful in diagnosis and pathophysiological research of iNPH.

METHODS

Probable iNPH and Alzheimer's disease (AD) patients were recruited. Clinical diagnosis was performed according to international guidelines. CSF collection complied with a standard protocol. Commercial accessible ELISA kits were introduced for measurement of CSF t-tau, p-tau181, Aβ42, and NfL.

RESULTS

Twenty-seven iNPH, 27 AD, and 18 controls were included. The profiles of CSF t-tau, p-tau181, and t-tau/Aβ42 in the iNPH and AD were significantly different (p < 0.0001). The profiles of CSF t-tau, p-tau181, and t-tau/Aβ42 in the iNPH and control were not different (p > 0.05). Level of CSF Aβ42 in iNPH was significantly lower than control (p < 0.0001) and also significantly higher than AD (p < 0.05). NfL level in iNPH and AD was increased, but its level in iNPH was significantly lower than that in AD (p = 0.005). NfL and t-tau level in the iNPH group was significantly correlated (coefficient = 0.649, p = 0.005), but not in AD (coefficient = 0.298, p = 0.157).

CONCLUSION

Alzheimer's CSF biomarker profile of iNPH subjects showed moderately decreased Aβ42 and normal t-tau, p-tau181, and t-tau/Aβ42, which was distinguishable from AD. The different profiles and correlation of t-tau and NfL suggested different pathophysiology of AD and iNPH. t-tau was relatively an AD-specific neurodegenerative biomarker compared to NfL.

Predictive Value of Cerebrospinal Fluid Biomarkers for Tap Test Responsiveness in Patients With Suspected Idiopathic Normal Pressure Hydrocephalus

Background: The value of cerebrospinal fluid (CSF) biomarkers for assessing idiopathic normal pressure hydrocephalus (iNPH) must be determined. This prospective study aimed to reveal the correlation between CSF biomarkers and clinical symptoms of iNPH and the predictive value of these biomarkers for tap test responsiveness.

Methods: Thirty-nine patients with suspected iNPH were recruited, contributed qualified CSF, and underwent a tap test and unified pre- and post-test evaluations of the neurological function.

Results: The analysis of biomarkers from the patients’ CSF showed decreased levels of tau and its phosphorylated form, especially in the tap test (+) group. The responsiveness of the tap test was also related to the number of combined symptoms (p < 0.01), and a correlation was found between the end pressure or pressure difference in CSF and tap test responsiveness (p < 0.05). The results of the binary logistic regression analysis showed that P (tap test responsiveness) = 1/1 + e^∧ − (−5.505 + 55.314 * ratio of p/T-tau − 1.586 * numbers of combined symptoms). The combined indicators (−5.505 + 0.553 * percentage of p/T-tau − 1.586 * numbers of combined symptoms) resulted in the highest sensitivity and specificity of 94.12% and 72.73%, respectively.

Conclusions: CSF biomarkers may be assessed to judge tap test responsiveness, which is beneficial for the feasibility of a clinical application.

Preoperative Predictive Factors of Short-Term Outcome in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

Surgical treatment of idiopathic normal pressure hydrocephalus (iNPH) by ventriculoperitoneal (VP) or lumboperitoneal (LP) shunting can achieve long-term recovery of activities of daily living; however, in a subset of patients, maintenance of independence lasted for <6 months. This study examined positive preoperative predictive factors of short-term outcome for shunted iNPH patients.

METHODS

Over a 9-year period, consecutive patients from multiple centers diagnosed with probable iNPH underwent either VP or LP shunt surgery. Preoperative variables of age, symptom duration, iNPH severity, tap test response, and magnetic resonance imaging findings of disproportionately enlarged subarachnoid space hydrocephalus (DESH) or incomplete DESH were retrospectively evaluated in relation to 1-year postoperative outcome.

RESULTS

Outcome for 154 shunt patients (12 VP, 142 LP) as measured by postoperative disability modified Rankin Scale (mRS) and iNPH-gait disturbance (GD) was the same regardless of age. Symptom duration was inversely correlated with both iNPH severity (P < 0.0001) and postoperative improvement at 1 year (P = 0.0015). Severity also correlated inversely with postoperative improvement at 1 year (P < 0.0001). Age was not significantly correlated with the degree of postoperative improvement (mRS: P = 0.487; iNPH grading scale [GD]: P = 0.725). Outcome at 1 year (mRS, gait domain, and activities of daily living significantly improved in patients with a good response to the tap test (P < 0.0001) Preoperative DESH correlated with improvement in mRS and GD (P < 0.0001).

CONCLUSIONS

Mild preoperative iNPH severity, shorter preoperative symptom duration, good tap test response, and complete DESH were associated with good short-term postoperative outcome at 1 year. These positive factors may be useful for prediction of short-term surgical outcome in iNPH patients.

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.

Revisiting the Cerebrospinal Fluid Biomarker Profile in Idiopathic Normal Pressure Hydrocephalus: The Bologna Pro-Hydro Study

Cerebrospinal fluid (CSF) biomarkers have been extensively investigated in idiopathic normal pressure hydrocephalus (iNPH) with the aim of a better differential diagnosis, but the pathophysiological mechanisms underlying CSF biomarker changes and the relationship between biomarker levels and clinical variables are still a matter of debate. We evaluated CSF amyloid-β (Aβ)42 and Aβ40, total (t)-tau, phosphorylated (p)-tau, total prion protein (t-PrP), and neurofilament light chain protein (NfL) in healthy controls (n = 50) and subjects with iNPH (n = 71), Alzheimer's disease (AD) (n = 60), and several other subtypes of dementia (n = 145). Patients with iNPH showed significantly lower levels of Aβ42, Aβ40, t-tau, and p-tau compared to controls. Similarly, t-PrP values showed a trend toward lower levels in iNPH patients than in controls. At variance, NfL levels were increased in iNPH as in all other neurodegenerative dementias, with no significant difference between "pure" iNPH cases and those with vascular or AD comorbidities. The Aβ42/Aβ40 ratio showed higher diagnostic value than Aβ42 alone in the differential diagnosis between iNPH and AD. There were no clinically relevant associations between neuroimaging markers, scores at clinical and cognitive scales/tests, or rates of response at tap test and CSF biomarker results. In summary, the CSF biomarker signature in patients with iNPH is mainly characterized by reduced CSF concentrations of Aβ- and tau-related proteins. The assessment of CSF neurodegenerative biomarker profile in iNPH, including the Aβ42/Aβ40 ratio, contributes to the differential diagnosis with AD and other dementias but shows poor associations with clinical variables.

Cerebrospinal Fluid Biomarkers in Idiopathic Normal Pressure Hydrocephalus versus Alzheimer's Disease and Subcortical Ischemic Vascular Disease: A Systematic Review

BACKGROUND

The diagnostic workup of idiopathic normal pressure hydrocephalus (iNPH) can be challenging due to an overlap in symptoms and neuroimaging features with other disorders. Despite a growing interest, a cerebrospinal fluid (CSF) biomarker profile in iNPH has not yet been identified.

OBJECTIVE

To determine the CSF biomarkers with the greatest evidence for differentiating iNPH from the most common differential diagnoses, Alzheimer's disease (AD) and subcortical ischemic vascular disease (SIVD).

METHODS

A systematic literature search was conducted in PubMed to identify relevant articles up to July 2018 using the following MESH-terms: "Cerebrospinal fluid", "diagnos*", "hydrocephalus, normal pressure". Relevant data were extracted to assess the risk of bias in the included studies.

RESULTS

Twenty-five studies including 664 patients with iNPH, 502 with AD, 57 with SIVD, 81 with other disorders, and 338 healthy controls (HC) were included. They investigated the diagnostic value of 92 CSF biomarkers. Most evidence existed for amyloid-β 42 (Aβ42), phosphorylated tau (p-tau), and total tau (t-tau) in iNPH versus AD and HC: Aβ42 did not differ between iNPH and AD, but was lower than in HC subjects. T-tau and p-tau were lower in iNPH versus AD on a level comparable to HC subjects. There was moderate or limited evidence for 62 and 88 biomarkers, respectively. Several plausible biases characterize the literature including small sample sizes and inconsistent diagnostic criteria.

CONCLUSION

T-tau and p-tau may differentiate iNPH from AD and Aβ42 from HC. A combination of these biomarkers may improve the diagnostic accuracy in iNPH.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Preoperative Phosphorylated Tau Concentration in the Cerebrospinal Fluid Can Predict Cognitive Function Three Years after Shunt Surgery in Patients with Idiopathic Normal Pressure Hydrocephalus

Background:

Idiopathic normal pressure hydrocephalus (iNPH) is commonly treated by cerebrospinal fluid (CSF) shunting. However, the long-term efficacy of shunt intervention in the presence of comorbid Alzheimer’s disease (AD) pathology is debated.

Objective:

To identify AD-associated CSF biomarkers predictive of shunting surgery outcomes in patients with iNPH.

Methods:

Preoperative levels of total and phosphorylated Tau (p-Tau) were measured in 40 patients with iNPH divided into low (<30 pg/mL) and high (≥30 pg/mL) p-Tau groups and followed up for three years after lumboperitoneal shunting. The modified Rankin Scale (mRS), Mini-Mental State Examination (MMSE), Frontal Assessment Battery, and iNPH Grading Scale scores were compared between the age-adjusted low (n = 24; mean age 75.7 years [SD 5.3]) and high (n = 11; mean age 76.0 years [SD 5.6]) p-Tau groups.

Results:

Cognitive function improved early in the low p-Tau group and was maintained thereafter (p = 0.005). In contrast, the high p-Tau group showed a gradual decline to baseline levels by the third postoperative year (p = 0.040). Although the p-Tau concentration did not correlate with the preoperative MMSE score, a negative correlation appeared and strengthened during follow-up (R² = 0.352, p < 0.001). Furthermore, the low p-Tau group showed rapid and sustained mRS grade improvement, whereas mRS performance gradually declined in the high p-Tau group.

Conclusions:

Preoperative CSF p-Tau concentration predicted some aspects of cognitive function after shunt intervention in patients with iNPH. The therapeutic effects of shunt treatment were shorter-lasting in patients with coexisting AD pathology.

Cerebrospinal Fluid Levels of β-Amyloid 40 and β-Amyloid 42 are Proportionately Decreased in Amyloid Positron-Emission Tomography Negative Idiopathic Normal-Pressure Hydrocephalus Patients

BACKGROUND AND PURPOSE

Cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) could be misleading in idiopathic normal-pressure hydrocephalus (iNPH). We therefore investigated the CSF biomarkers in 18F-florbetaben amyloid-negative positron-emission tomography (PET) [amyloid PET(-)] iNPH, amyloid-positive PET [amyloid PET(+)] AD, and cognitively normal (CN) subjects.

METHODS

Ten amyloid PET(+) AD patients (56.7±5.6 years old, mean±standard deviation), 10 amyloid PET(-) iNPH patients (72.8±4.5 years old), and 8 CN subjects (61.2±6.5 years old) were included. We measured the levels of β-amyloid (Aβ)40, Aβ42, total tau (t-tau) protein, and phosphorylated tau (p-tau) protein in the CSF using enzyme-linked immunosorbent assays.

RESULTS

The level of Aβ42 and the Aβ42/Aβ40 ratio in the CSF were significantly lower in AD than in iNPH or CN subjects. The Aβ40 level did not differ significantly between AD and iNPH (p=1.000), but it did between AD and CN subjects (p=0.032). The levels of both t-tau and p-tau were higher in AD than in iNPH or CN subjects. The levels of Aβ42, Aβ40, t-tau, and p-tau were lower in iNPH than in CN subjects, but there was no significant difference after controlling for age.

CONCLUSIONS

Our results suggest that the mechanism underlying low CSF Aβ levels differs between amyloid PET(-) iNPH and amyloid PET(+) AD subjects. The lower levels of all CSF biomarkers in iNPH patients might be due to reduced clearances from extracellular fluid and decreased brain metabolism of the periventricular zone in iNPH resulting from glymphatic dysfunction.

Cerebrospinal Fluid Amyloid-β 42, Total Tau and Phosphorylated Tau are Low in Patients with Normal Pressure Hydrocephalus: Analogies and Differences with Alzheimer's Disease

Co-existence of Alzheimer's disease (AD) in normal pressure hydrocephalus (NPH) is a frequent finding, thus a common pathophysiological basis between AD and NPH has been postulated. We measured CSF amyloid-β 42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) concentrations in a sample of 294 patients with different types of dementia and 32 subjects without dementia. We then compared scores on neuropsychological tests of NPH patients with pathological and normal CSF Aβ42 values. Aβ42 levels were significantly lower in NPH than in control patients, with no significant differences between AD and NPH. On the contrary, t-tau and p-tau levels were significantly lower in NPH than in AD, with no differences between NPH and controls. NPH patients with pathological Aβ42 levels did not perform worse than NPH patients with normal Aβ42 levels in any cognitive domains. Our data seem to support the hypothesis of amyloid accumulation in brains of NPH patients. Nevertheless, amyloid does not seem to play a pathogenetic role in the development of cognitive deficits in NPH.

Changes of cerebrospinal fluid protein concentrations and gait patterns in geriatric normal pressure hydrocephalus patients after ventriculoperitoneal shunting surgery

Normal pressure hydrocephalus (NPH) was the first type of dementia ever described that can be treated using ventriculoperitoneal shunting surgery. Three typical clinical symptoms of NPH include gait disturbance, progressive cognitive dysfunction, and urinary incontinence. Although there are articles that have discovered several cerebrospinal fluid (CSF) protein biomarkers associated with NPH; however, studies examining individual and total protein concentrations from the ventricular CSF before and after shunting surgery are lacking. This study used proteomics to calculate the CSF individual and total protein concentrations before, and one week, one month and three months after the shunting surgery. Parameters of cadence, step length, walking speed, and percentages of single- and double-limb support in a gait cycle were measured. Protein concentrations associated with anti-oxidation, aging, and in the prevention of neurotoxic agent production increased by at least 2-folds after the surgery, indicating that the brain may become less susceptible to neurodegeneration. These proteins were alpha-1B-glycoprotein, apolipoproteins A-1 & A-IV, prostaglandin-H2 D-isomerase, alpha-1-antitrypsin, and serotransferrin. In gait analysis, lower cadence, decreased double-limb support, longer step length, and increased single-limb support were observed after the surgery, indicating a more stable walking balance. These changes lasted for a period of at least 3 months. As a result, shunting surgery may be recommended for geriatric patients with confirmed diagnosis of normal pressure hydrocephalus.

Change of Amyloid-β 1-42 Toxic Conformer Ratio After Cerebrospinal Fluid Diversion Predicts Long-Term Cognitive Outcome in Patients with Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

Alzheimer's disease (AD) pathology in idiopathic normal pressure hydrocephalus (iNPH) contributes to poor shunt responses. Amyloid-β 1- 42 (Aβ42) toxic conformer was recently identified with features of rapid oligomerization, strong neurotoxicity and synaptotoxicity.

OBJECTIVE

This observational study points to Aβ42 toxic conformer as a biomarker for AD pathology and for poor postoperative prognosis in patients with iNPH.

METHODS

The first cohort consisted of patients with AD (n = 17) and iNPH (n = 17), and cognitively normal individuals (CN, n = 12). The second cohort, consisted of 51 patients with iNPH, was divided into two groups according to phosphorylated Tau (pTau) level (low- and high-pTau groups); the low-pTau group was further subdivided according to one-year postoperative change in Aβ42 toxic conformer ratio (%) [Aβ42 toxic conformer/Aβ42×100] (decreased- and increased-conformer subgroups). Enzyme-linked immunosorbent assay was used to measure pTau, Aβ42, and Aβ42 toxic conformer in cerebrospinal fluid. Outcomes were evaluated using neuropsychological tests one- and two-years postoperatively.

RESULTS

In the first cohort, Aβ42 toxic conformer ratio in the iNPH group (10.8%) was significantly higher than that in the CN group (6.3%) and significantly lower than that in the AD group (17.2%). In the second cohort, the high-pTau group showed cognitive decline two-years postoperatively compared to baseline. However, the low-pTau group showed favorable outcomes one-year postoperatively; furthermore, the increased-conformer subgroup showed cognitive decline two-years postoperatively while the decreased-conformer subgroup maintained the improvement.

CONCLUSIONS

Change in Aβ42 toxic conformer ratio predicts long-term cognitive outcome in iNPH, even in the low-pTau group.

Prognostic value of amyloid PET scan in normal pressure hydrocephalus

Amyloid positron emission tomography ([18F] florbetaben (FBB) PET) can be used to determine concomitant Alzheimer's disease (AD) in idiopathic normal pressure hydrocephalus (iNPH) patients. FBB PET scans and the tap test were performed in 31 patients with clinically suspected iNPH, and amyloid positive (iNPH/FBB+) and negative (iNPH/FBB-) groups were compared with respect to clinical characteristics. We evaluated prognostic value of FBB PET scans by analyzing the response to the tap test using a linear mixed model. We also performed a multivariable regression analysis to investigate whether amyloid PET positivity can predict the positive tap test response independent of other AD biomarkers. The results showed that the iNPH/FBB+ group (7/31, 22.6%) had a higher percentage of APOE4 carriers, lower Aβ42, higher CSF t-tau, and p-tau/Aβ42 ratio than the iNPH/FBB- group (24/31, 77.4%), while the two groups did not differ in imaging characteristics. The iNPH/FBB- group had a higher percentage of tap responders and showed a greater improvement in gait scores after the tap test than the iNPH/FBB+ group (group-tap test effect interaction, p = 0.035). A multivariable logistic regression analysis showed that amyloid positivity on PET scans (OR 0.03, p = 0.029) and CSF p-tau (OR 0.87, p = 0.044) were independently associated with the positive tap test response. Among 21 tap responders in the iNPH/FBB- group, 14 patients received shunt surgery and 12/14 (85.7%) patients showed symptom improvement. Our findings suggest that amyloid PET scans can help determine which iNPH patients will benefit from shunt surgery by discriminating concomitant AD.

Cerebrospinal fluid Aβ42, t-tau, and p-tau levels in the differential diagnosis of idiopathic normal-pressure hydrocephalus: a systematic review and meta-analysis

Objectives

The purpose of this systematic review and meta-analysis was to evaluate the performance of cerebrospinal fluid (CSF) beta amyloid 42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) as potential diagnostic biomarkers for idiopathic normal-pressure hydrocephalus (iNPH) and to assess their utility indistinguishing patients with iNPH from those with Alzheimer disease (AD) and healthy normal controls.

Methods

Studies were identified by searching PubMed, Embase, the Cochrane Library, Web of Science, Chinese National Knowledge Infrastructure (CNKI), Wanfang Chinese Periodical Database, VIP Chinese database, and Chinese Bio-medicine Database (CBM) before August 2016. The standardized mean difference (SMD) and 95% confidence interval (CI), comparing CSF Aβ42, t-tau, and p-tau levels between iNPH, AD and healthy controls, were calculated using random-effects models. Subgroup analyses were created according to ethnicity (Caucasian or Asian) and CSF type (lumbar or ventricular), and the publication bias was estimated using Egger’s test and the Begg’s test.

Results

A total of 10 studies including 413 patients with iNPH, 186 patients with AD and 147 healthy controls were included in this systematic review and meta-analysis. The concentrations of CSF t-tau, and p-tau were significantly lower in iNPH patients compared to AD (SMD = −1.26, 95% CI −1.95 to −0.57, P = 0.0004; SMD = −1.54, 95% CI −2.34 to −0.74, P = 0.0002, respectively) and lower than healthy controls (SMD = −0.80, 95% CI −1.50 to −0.09, P = 0.03; SMD = −1.12, 95% CI −1.38 to −0.86, P < 0.00001, respectively). Patients with iNPH had significantly lower Aβ42 levels compared with controls (SMD = −1.14, 95% CI −1.74 to −0.55, P = 0.0002), and slightly higher Aβ42 levels compared with AD patients (SMD = 0.32, 95% CI 0.00–0.63, P = 0.05). Subgroup analyses showed that the outcomes may have been influenced by ethnicity and CSF source. Compared to AD, overall sensitivity in differentiating iNPH was 0.813 (95% CI 0.636–0.928) for Aβ42, 0.828 (95% CI 0.732–0.900) for t-tau, 0.943 (95% CI 0.871–0.981) for p-tau. Relative to AD, overall specificity in differentiating iNPH was 0.506 (95% CI 0.393–0.619) for Aβ42, 0.842 (95% CI 0.756–0.907) for t-tau, 0.851 (95% CI 0.767–0.914) for p-tau.

Conclusion

The results of our meta-analysis suggest that iNPH may be associated with significantly reduced levels of CSF Aβ42, t-tau and p-tau compared to the healthy normal state. Compared to AD, both t-tau and p-tau were significantly decreased in iNPH, but CSF Aβ42 was slightly increased. Prospective studies are needed to further assess the clinical utility of these and other CSF biomarkers in assisting in the diagnosis of iNPH and differentiating it from AD and other neurodegenerative disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s12987-017-0062-5) contains supplementary material, which is available to authorized users.

Cerebrospinal fluid biomarkers of infantile congenital hydrocephalus

Introduction

Hydrocephalus is a complex neurological disorder with a pervasive impact on the central nervous system. Previous work has demonstrated derangements in the biochemical profile of cerebrospinal fluid (CSF) in hydrocephalus, particularly in infants and children, in whom neurodevelopment is progressing in parallel with concomitant neurological injury. The objective of this study was to examine the CSF of children with congenital hydrocephalus (CHC) to gain insight into the pathophysiology of hydrocephalus and identify candidate biomarkers of CHC with potential diagnostic and therapeutic value.

Methods

CSF levels of amyloid precursor protein (APP) and derivative isoforms (sAPPα, sAPPβ, Aβ₄₂), tau, phosphorylated tau (pTau), L1CAM, NCAM-1, aquaporin 4 (AQP4), and total protein (TP) were measured by ELISA in 20 children with CHC. Two comparative groups were included: age-matched controls and children with other neurological diseases. Demographic parameters, ventricular frontal-occipital horn ratio, associated brain malformations, genetic alterations, and surgical treatments were recorded. Logistic regression analysis and receiver operating characteristic curves were used to examine the association of each CSF protein with CHC.

Results

CSF levels of APP, sAPPα, sAPPβ, Aβ₄₂, tau, pTau, L1CAM, and NCAM-1 but not AQP4 or TP were increased in untreated CHC. CSF TP and normalized L1CAM levels were associated with FOR in CHC subjects, while normalized CSF tau levels were associated with FOR in control subjects. Predictive ability for CHC was strongest for sAPPα, especially in subjects ≤12 months of age (p<0.0001 and AUC = 0.99), followed by normalized sAPPβ (p = 0.0001, AUC = 0.95), tau, APP, and L1CAM. Among subjects ≤12 months, a normalized CSF sAPPα cut-point of 0.41 provided the best prediction of CHC (odds ratio = 528, sensitivity = 0.94, specificity = 0.97); these infants were 32 times more likely to have CHC.

Conclusions

CSF proteins such as sAPPα and related proteins hold promise as biomarkers of CHC in infants and young children, and provide insight into the pathophysiology of CHC during this critical period in neurodevelopment.

Correlations between mini-mental state examination score, cerebrospinal fluid biomarkers, and pathology observed in brain biopsies of patients with normal-pressure hydrocephalus

Alzheimer disease (AD)-related pathology was assessed in cortical biopsy samples of 111 patients with idiopathic normal-pressure hydrocephalus. Alzheimer disease hallmark lesions-β-amyloid (Aβ) and hyperphosphorylated tau (HPtau)-were observed in 47% of subjects, a percentage consistent with that for whole-brain assessment reported postmortem in unselected cohorts. Higher-immunostained area fraction of AD pathology corresponded with lower preoperative mini-mental state examination scores. Concomitant Aβ and HPtau pathology, reminiscent of that observed in patients with AD, was observed in 22% of study subjects. There was a significant correlation between Aβ-immunostained area fraction in tissue and Aβ42 (42-amino-acid form of Aβ) in cerebrospinal fluid (CSF). Levels of Aβ42 were significantly lower in CSF in subjects with concomitant Aβ and HPtau pathology compared with subjects lacking pathology. Moreover, a significant correlation between HPtau-immunostained area fraction and HPtau in CSF was noted. Both HPtau and total tau were significantly higher in CSF in subjects with concomitant Aβ and HPtau pathology compared with subjects lacking pathology. The 42-amino-acid form of Aβ (Aβ42) and HPtau in CSF were the most significant predictors of the presence of AD pathology in cortical biopsies. Long-term follow-up studies are warranted to assess whether all patients with idiopathic normal-pressure hydrocephalus with AD pathology progress to AD and to determine the pathologic substrate of idiopathic normal-pressure hydrocephalus.

A consensus in Korea regarding a protocol to reduce preanalytical sources of variability in the measurement of the cerebrospinal fluid biomarkers of Alzheimer's disease

Cerebrospinal fluid (CSF) can provide vital informative about pathological processes occurring in the brain. In particular, the CSF concentrations of Aβ42, tTau, and pTau181 are useful for the early diagnosis of Alzheimer's disease (AD). However, many studies have demonstrated that confounding factors related to the preanalytical processing of CSF can seriously influence measurements of these AD biomarkers. It is therefore important to develop a standardized protocol for the acquisition and handling of CSF, particularly with regard to the types of tube used for collection and storage, the proper aliquot volume, blood contamination, and the number of tube transfers and freeze-thaw cycles, because these aspects of the procedure have been shown to affect AD biomarker measurements. A survey of the impact of several individual preanalytical procedures on the measurement of AD biomarkers in CSF was conducted for this review article, and the implications of the differences among them are discussed. Furthermore, following a review of the procedures used in Korean and international biomarker laboratories, a consensus was reached among a cooperative Korean multicenter research group regarding a standardized protocol for the analysis of AD biomarkers in CSF. All efforts were made to be stringent regarding the controversial issues associated with this protocol, thus minimizing the confounding influence of various factors on current investigations using established AD biomarkers and on future studies using novel biomarkers of AD and other neurodegenerative disorders.