Alzheimer's disease pathology and shunt surgery outcome in normal pressure hydrocephalus

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.

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.

Longitudinal post-shunt outcomes in idiopathic normal pressure hydrocephalus with and without comorbid Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) is highly comorbid with idiopathic normal pressure hydrocephalus (iNPH) and may diminish the benefits of shunting; however, findings in this area are mixed. We examined postoperative outcomes, with emphases on cognition and utilization of novel scoring procedures to enhance sensitivity.

METHODS

Using participant data from an iNPH outcome study at Butler Hospital, a mixed effect model examined main and interaction effects of time since surgery (baseline, 3 months, 12 months, and 24-60 months) and AD comorbidity (20 iNPH and 11 iNPH+AD) on activities of daily living (ADLs) and iNPH symptoms. Regression modeling explored whether baseline variables predicted improvements 3 months postoperatively.

RESULTS

There were no group differences in gait, incontinence, and global cognition over time, and neither group showed changes in ADLs. Cognitive differences were observed postoperatively; iNPH patients showed stable improvements in working memory (p = 0.012) and response inhibition (p = 0.010), while iNPH + AD patients failed to maintain initial gains. Regarding predicting postoperative outcomes, baseline AD biomarkers did not predict shunt response at 3 months; however, older age at surgery predicted poorer cognitive outcomes (p = 0.04), and presurgical Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) (p = 0.035) and Mini-Mental Status Examination (MMSE) scores (p = 0.009) predicted improvements incontinence.

CONCLUSION

iNPH + AD may be linked with greater declines in aspects of executive functioning postoperatively relative to iNPH alone. While baseline AD pathology may not prognosticate shunt response, younger age appears linked with postsurgical cognitive improvement, and utilizing both brief and comprehensive cognitive measures may help predict improved incontinence. These results illustrate the potential benefits of surgery and inform postoperative expectations for those with iNPH + AD.

[Coincidence of normal pressure hydrocephalus and Alzheimer`s disease: therapeutic implications and open questions]

Normal pressure hydrocephalus (NPH) is prevalent in aging patient populations. Despite its clinical relevance, many patients with NPH may not receive adequate treatment. Because of the frequency of Alzheimer`s disease in these patients, there could be overlapping pathophysiological mechanisms that are as yet incompletely understood. Cerebral comorbidities seem to have negative effects on therapeutic response to ventriculoperitoneal shunting. In order to avoid unnecessary and unsuccessful surgery in highly vulnerable elderly patients, they have to be taken into consideration in the diagnostic process.

Idiopathic normal pressure hydrocephalus: historical context and a contemporary guide

Idiopathic normal pressure hydrocephalus (NPH) was described in 1965 as a syndrome in which hydrocephalus develops but with a normal cerebrospinal fluid (CSF) pressure, causing shunt-responsive gait apraxia, cognitive impairment and urinary incontinence. Not all patients respond to shunting despite having the clinical syndrome with appropriate radiological features. This has led to considerable debate over subsequent decades regarding idiopathic NPH. It is now understood that asymptomatic communicating hydrocephalus can develop in many healthy older people, and that over time this can develop into a symptomatic state that sometimes responds to CSF shunting, but to a variable extent. This review looks at the historical background of NPH, the use of predictive tests, the current state of clinical evidence for the diagnosis and treatment of idiopathic NPH and the possible underlying causes, to provide a contemporary practical guide for assessing patients with the radiological features of idiopathic NPH.

Clinical Features of Idiopathic Normal Pressure Hydrocephalus: Critical Review of Objective Findings

Background

Idiopathic normal pressure hydrocephalus (iNPH) is characterized by the classic clinical triad of gait, cognitive, and urinary dysfunction, albeit incomplete in a relevant proportion of patients. The clinical findings and evolution of these symptoms have been variably defined in the literature.

Objectives

To evaluate how the phenomenology has been defined, assessed, and reported, we performed a critical review of the existing literature discussing the phenomenology of iNPH. The review also identified the instrumental tests most frequently used and the evolution of clinical and radiologic findings.

Methods

The review was divided into 3 sections based on gait, cognitive, and urinary dysfunction. Each section performed a literature search using the terms "idiopathic normal pressure hydrocephalus" (iNPH), with additional search terms used by each section separately. The number of articles screened, duplicates, those meeting the inclusion criteria, and the number of articles excluded were recorded. Findings were subsequently tallied and analyzed.

Results

A total of 1716 articles with the aforementioned search criteria were identified by the 3 groups. A total of 81 full-text articles were reviewed after the elimination of duplicates, articles that did not discuss phenomenological findings or instrumental testing of participants with iNPH prior to surgery, and articles with fewer than 10 participants.

Conclusions

"Wide-based gait" was the most common gait dysfunction identified. Cognitive testing varied significantly across articles, and ultimately a specific cognitive profile was not identified. Urodynamic testing found detrusor overactivity and "overactive bladder" as the most common symptom of urinary dysfunction.

Idiopathic normal pressure hydrocephalus and frontotemporal dementia: an unexpected association

Idiopathic normal pressure hydrocephalus has a complex multifactorial pathogenesis and is associated with Alzheimer's disease in many patients. To date, it is not well known if a similar association exists with behavioural variant of frontotemporal lobar degeneration. In a first step, we compare the prevalence of idiopathic normal pressure hydrocephalus in two groups of patients, one with behavioural variant of frontotemporal lobar degeneration (n = 69) and the other with Alzheimer's disease (n = 178). In the second step, we describe more precisely the phenotype of patients with the association of idiopathic normal pressure hydrocephalus and behavioural variant of frontotemporal lobar degeneration. Firstly, we report that the prevalence of idiopathic normal pressure hydrocephalus was far higher in the group of patients with behavioural variant of frontotemporal lobar degeneration than in the group of patients with Alzheimer's disease (7.25% and 1.1%, respectively, P = 0.02). Secondly, we show that patients with the double diagnosis share common clinical and para-clinical features of both idiopathic normal pressure hydrocephalus and behavioural variant of frontotemporal lobar degeneration patients, including CSF shunting efficacy in real-life experience. Overall, our results suggest a link between these two conditions and should encourage neurologists to look for idiopathic normal pressure hydrocephalus in their behavioural variant of frontotemporal lobar degeneration patients in the event of gait disturbances; the benefit/risk balance could indeed be in favour of shunt surgery for selected patients with this newly described entity.

Ventricular volume in relation to lumbar CSF levels of amyloid-β 1–42, tau and phosphorylated tau in iNPH, is there a dilution effect?

Background

Levels of the biomarkers amyloid-β 1–42 (Aβ42), tau and phosphorylated tau (p-tau) are decreased in the cerebrospinal fluid (CSF) of patients with idiopathic normal pressure hydrocephalus (iNPH). The mechanism behind this is unknown, but one potential explanation is dilution by excessive CSF volumes. The aim of this study was to investigate the presence of a dilution effect, by studying the relationship between ventricular volume (VV) and the levels of the CSF biomarkers.

Methods

In this cross-sectional observational study, preoperative magnetic resonance imaging (MRI) and lumbar CSF was acquired from 136 patients with a median age of 76 years, 89 men and 47 females, selected for surgical treatment for iNPH. The CSF volume of the lateral and third ventricles was segmented on MRI and related to preoperative concentrations of Aβ42, tau and p-tau.

Results

In the total sample VV (Median 140.7 mL) correlated weakly (rs = − 0.17) with Aβ42 (Median 534 pg/mL), but not with tau (Median 216 pg/mL) nor p-tau (Median 31 pg/mL). In a subgroup analysis, the correlation between VV and Aβ42 was only present in the male group (rs = − 0.22, p = 0.038). Further, Aβ42 correlated positively with tau (rs = 0.30, p = 0.004) and p-tau (rs = 0.26, p = 0.012) in males but not in females.

Conclusions

The findings did not support a major dilution effect in iNPH, at least not in females. The only result in favor for dilution was a weak negative correlation between VV and Aβ42 but not with the other lumbar CSF biomarkers. The different results between males and females suggest that future investigations of the CSF pattern in iNPH would gain from sex-based subgroup analysis.

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.

Clinical Outcomes After Ventriculo-Peritoneal Shunting in Patients With Classic vs. Complex NPH

Objective

Normal pressure hydrocephalus (NPH) is a neurological condition characterized by a clinical triad of gait disturbance, cognitive impairment, and urinary incontinence in conjunction with ventriculomegaly. Other neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and vascular dementia share some overlapping clinical features. However, there is evidence that patients with comorbid NPH and Alzheimer's or Parkinson's disease may still exhibit good clinical response after CSF diversion. This study aims to evaluate clinical responses after ventriculo-peritoneal shunt (VPS) in a cohort of patients with coexisting NPH and neurodegenerative disease.

Methods

The study has two components; (i) a pilot study was performed that specifically focused upon patients with Complex NPH and following the inclusion of the Complex NPH subtype into consideration for the clinical NPH programme, (ii) a retrospective snapshot study was performed to confirm and characterize differences between Classic and Complex NPH patients being seen consecutively over the course of 1 year within a working subspecialist NPH clinic. We studied the characteristics of patients with Complex NPH, utilizing clinical risk stratification and multimodal biomarkers.

Results

There was no significant difference between responders and non-responders to CSF diversion on comorbidity scales. After VPS insertion, significantly more Classic NPH patients had improved cognition compared to Complex NPH patients (p = 0.005). Improvement in gait and urinary symptoms did not differ between the groups. 26% of the Classic NPH group showed global improvement of the triad, and 42% improved in two domains. Although only 8% showed global improvement of the triad, all Complex NPH patients improved in gait.

Conclusions

Our study has demonstrated that the presence of neurodegenerative disorders co-existing with NPH should not be the sole barrier to the consideration of high-volume tap test or lumbar drainage via a specialist NPH programme. Further characterization of distinct cohorts of NPH with differing degrees of CSF responsiveness due to overlay from neurodegenerative or comorbidity risk burden may aid toward more precise prognostication and treatment strategies. We propose a simplistic conceptual framework to describe NPH by its Classic vs. Complex subtypes to promote the clinical paradigm shift toward subspecialist geriatric neurosurgery by addressing needs for rapid screening tools at the clinical-research interface.

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

Lumbar-peritoneal shunt for idiopathic normal pressure hydrocephalus and secondary normal pressure hydrocephalus

Objectives:

Normal-pressure hydrocephalus is a clinical syndrome consisting of dilated cerebral ventricles with the clinical triad of gait disturbance, cognitive impairment and/or urinary dysfunction. Lumbar-peritoneal (LP) shunt could improve idiopathic normal pressure hydrocephalus (iNPH) while its effectiveness on secondary NPH (sNPH) is elusive. We compared the clinical results of the patients who received LP shunt surgery between iNPH and sNPH.

Materials and Methods:

We retrospectively analyzed the patients who received LP shunt surgery in a single center from January 1, 2017, to June 30, 2017. Patients selected for LP shunt placement had at least two of three cardinal symptoms of iNPH. The symptoms should persist for more than 3 months with compatible brain magnetic resonance imaging findings. All patients were followed up with iNPH grading scale (iNPHGS) and Modified Rankin Scale (MRS) for evaluation.

Results:

Thirty-three patients (23 male and 10 female patients) with mean age 76-year-old completed follow-up in this study, and 17 patients received lumbar drainage tests and intracranial pressure measurements. Both iNPH (n = 22) and sNPH (n = 11) groups did not have major complications such as infection, nerve root injury, or shunt failure. Both groups have significant improvement in iNPHGS and MRS. Interestingly, we found the correlation between both opening intracranial pressure and pressure gradient difference to the improvement percentage from LP shunt.

Conclusion:

The safety and effectiveness for sNPH patients who received LP shunt placement are equivalent to the iNPH patients. Lumbar drainage test provides prerequisite outcome prediction and should be considered to identify NPH patients planned to receive LP shunt.

Alzheimer's Disease Biomarkers in Idiopathic Normal Pressure Hydrocephalus: Linking Functional Connectivity and Clinical Outcome

BACKGROUND

Alzheimer's disease (AD) pathology impacts the response to treatment in patients with idiopathic normal pressure hydrocephalus (iNPH), possibly through changes in resting-state functional connectivity (rs-FC).

OBJECTIVE

To explore the relationship between cerebrospinal fluid biomarkers of AD and the default mode network (DMN)/hippocampal rs-FC in iNPH patients, based on their outcome after cerebrospinal fluid tap test (CSFTT), and in patients with AD.

METHODS

Twenty-six iNPH patients (mean age: 79.9±5.9 years; 12 females) underwent MRI and clinical assessment before and after CSFTT and were classified as responders (Resp) or not (NResp), based on the improvement at the timed up and go test and walking speed. Eleven AD patients (mean age: 70.91±5.2 years; 5 females), matched to iNPH for cognitive status, were also included. DMN and hippocampal rs-FC was related to amyloid-β42 and phosphorylated tau (pTau) levels.

RESULTS

Lower amyloid-β42 levels were associated with reduced inter- and intra-network rs-FC in NResp, and the interaction between amyloid-β42 and rs-FC was a predictor of outcome after CSFTT. The rs-FC between DMN and salience networks positively correlated to amyloid-β42 levels in both NResp and AD patients. The increase in the inter-network rs-FC after CSFTT was associated with higher pTau and lower amyloid-β42 levels in NResp, and to lower pTau levels in Resp.

CONCLUSION

Amyloid-β42 and pTau impact on rs-FC and its changes after CSFTT in iNPH patients. The interaction between AD biomarkers and rs-FC might explain the responder status in iNPH.

Evaluation of the effect comorbid Parkinson syndrome on normal pressure hydrocephalus assessment

OBJECTIVE

The primary aim of the study was to assess the effect comorbid Parkinson syndromes have on results of CSF tap test (TT) and shunt outcomes for patients presenting with Normal Pressure Hydrocephalus (NPH). We hypothesized that patients with possible NPH and comorbid Parkinson syndromes with Positive DaT scans will not respond to CSF TT at the same rate as patients without comorbid Parkinson syndromes. Additionally, we followed a small number of patients with positive DaT scans who were shunted to assess long term outcome of comorbid Parkinson syndromes.

METHODS

Medical records and neurological exams of 251 patients were reviewed. In our analysis 101 patients with no parkinsonian symptoms and no DaT scans were included as a control group, there were 52 patients with DaT scans, 31 patients were positive (DaT-P). Gait measures were assessed before and after CSF TT using the Wilcoxon matched-pairs signed-rank test or paired t-tests were used. To compare the effect of DaT-P and Control, we used an ANCOVA controlling for age, sex, assistive device used, and past medical history effecting gait.

RESULTS

There was not a significant difference in response between Control and DaT-P group. The Control group improved on timed up and go (TUG) by 14.82%, DualTUG 16.35%, 10-meter Walk Test (10MWT) 18.13%, MiniBEST 15.91%, and 6-minute Walk Test (6MWT) 13.96%, while the DaT-P group improved on TUG by 14.93%, DualTUG 17.24%, 10MWT 22.68%, MiniBEST 18.07%, and 6MWT 16.06%.

CONCLUSION

Our findings suggest that patients with possible NPH and suspected comorbid movement disorder, showed similar improvement after diagnostic CSF TT compared to participants with no parkinsonian symptoms present on exam.

DATA AVAILABILITY STATEMENT

Data relevant to the study will be made available from the corresponding author upon a reasonable request.

Differences in Brain Morphology between Hydrocephalus Ex Vacuo and Idiopathic Normal Pressure Hydrocephalus

OBJECTIVE

The distinction between idiopathic normal pressure hydrocephalus (iNPH) and hydrocephalus ex vacuo caused by encephalic volume loss remains to be established. This study aims to investigate radiological parameters as clinically useful tools to discriminate iNPH from hydrocephalus ex vacuo caused by Alzheimer's disease (AD).

METHODS

A total of 54 patients with ventriculomegaly (iNPH, 25; hydrocephalus ex vacuo, 29) were recruited in this study. Consequently, nine radiological parameters were compared between iNPH and hydrocephalus ex vacuo using magnetic resonance imaging (MRI).

RESULTS

A small callosal angle (CA), the Sylvian fissure dilatation, and absence of narrowing of superior parietal sulci discriminated the iNPH group from the hydrocephalus ex vacuo group (p<0.05). The final binary logistic regression model included narrowing of superior parietal sulci, degrees of the CA, and height of the Sylvian fissure after controlling for age and global Clinical Dementia Rating (CDR). The composite score made from these three indicators (narrowing of superior parietal sulci, degrees of the CA, and height of the Sylvian fissure) was statistically different between iNPH and hydrocephalus ex vacuo.

CONCLUSION

The narrowing of the CA, dilatation of the Sylvain fissure, and narrowing of superior parietal sulci may be used as radiological key indices and noninvasive tools for the differential diagnosis of iNPH from hydrocephalus ex vacuo.

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.

CSF Dynamics for Shunt Prognostication and Revision in Normal Pressure Hydrocephalus

BACKGROUND

Despite the quantitative information derived from testing of the CSF circulation, there is still no consensus on what the best approach could be in defining criteria for shunting and predicting response to CSF diversion in normal pressure hydrocephalus (NPH).

OBJECTIVE

We aimed to review the lessons learned from assessment of CSF dynamics in our center and summarize our findings to date. We have focused on reporting the objective perspective of CSF dynamics testing, without further inferences to individual patient management.

DISCUSSION

No single parameter from the CSF infusion study has so far been able to serve as an unquestionable outcome predictor. Resistance to CSF outflow (Rout) is an important biological marker of CSF circulation. It should not, however, be used as a single predictor for improvement after shunting. Testing of CSF dynamics provides information on hydrodynamic properties of the cerebrospinal compartment: the system which is being modified by a shunt. Our experience of nearly 30 years of studying CSF dynamics in patients requiring shunting and/or shunt revision, combined with all the recent progress made in producing evidence on the clinical utility of CSF dynamics, has led to reconsidering the relationship between CSF circulation testing and clinical improvement.

CONCLUSIONS

Despite many open questions and limitations, testing of CSF dynamics provides unique perspectives for the clinician. We have found value in understanding shunt function and potentially shunt response through shunt testing in vivo. In the absence of infusion tests, further methods that provide a clear description of the pre and post-shunting CSF circulation, and potentially cerebral blood flow, should be developed and adapted to the bed-space.

Frontal Dysexecutive Syndrome in Brain Tumors: A Pragmatic Insight to an Old Problem

Brain tumors have long been considered one of the most prevalent causes of potentially reversible cognitive impairment. An accurate underlying cause of cognitive impairment due to brain tumor needs to be evaluated pragmatically. Patterns of cognitive impairment associated with brain tumors depend mainly on their location, lateralization, pathological classification and secondary effects of the treatment, as well as the structural plasticity and diaschisis. Hence, it is not rare that lesions with different locations and histologies may manifest with a similar pattern of cognitive impairment due to the complex interplay of determinants. We herein report 3 patients with brain tumors affecting different locations and with differing histologies, who shared a similar presentation as “frontal dysexecutive syndrome” masqueraded as psychiatric conditions. Detailed examination of saccades and pursuit along with eye movements and conventional motor examinations were essential not only to diagnose brain tumor as the potential cause of cognitive impairment, but also to rule out other coexisting etiologies with completely different underlying pathological mechanisms (i.e., Huntington's disease in 1 of the cases). A detailed neurological examination, including eye movement assessment, in patients with psychiatric symptoms provides not only important clues to delineate the underlying anatomical substrate involved, but also helps clinicians to make an accurate diagnosis and to select appropriate therapeutic options.

Normalized power variance of eLORETA at high-convexity area predicts shunt response in idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a neuropsychiatric disease characterized by gait disturbance, cognitive deterioration and urinary incontinence associated with excessive accumulation of cerebrospinal fluid (CSF) in the brain ventricles. These symptoms, in particular gait disturbance, can be potentially improved by shunt operation in the early stage of the disease, and the intervention associates with a worse outcome when performed late during the course of the disease. Despite the variable outcome of shunt operation, noninvasive presurgical prediction methods of shunt response have not been established yet. In the present study, we used normalized power variance (NPV), a sensitive measure of the instability of cortical electrical activity, to analyze cortical electrical activity derived from EEG data using exact-low-resolution-electromagnetic-tomography (eLORETA) in 15 shunt responders and 19 non-responders. We found that shunt responders showed significantly higher NPV values at high-convexity areas in beta frequency band than non-responders. In addition, using this difference, we could discriminate shunt responders from non-responders with leave-one-subject-out cross-validation accuracy of 67.6% (23/34) [positive predictive value of 61.1% (11/18) and negative predictive value of 75.0% (12/16)]. Our findings indicate that eLORETA-NPV can be a useful tool for noninvasive prediction of clinical response to shunt operation in patients with iNPH.

Prevalence of Alternative Diagnoses and Implications for Management in Idiopathic Normal Pressure Hydrocephalus Patients

BACKGROUND

Following Bayes theorem, ventriculomegaly and ataxia confer only a 30% chance of idiopathic Normal Pressure Hydrocephalus (NPH). When coupled with positive responses to best diagnostic testing (extended lumbar drainage), 70% of patients recommended for shunting will not actually have NPH. This is inadequate clinical care.

OBJECTIVE

To determine the proportion of alternative and treatable diagnoses in patients referred to a multidisciplinary NPH clinic.

METHODS

Patients without previously diagnosed NPH were queried from prospectively collected data. At least 1 neurosurgeon, cognitive neurologist, and neuropsychologist jointly formulated best treatment plans.

RESULTS

Of 328 total patients, 45% had an alternative diagnosis; 11% of all patients improved with treatment of an alternative diagnosis. Of 87 patients with treatable conditions, the highest frequency of pathologies included sleep disorders, and cervical stenosis, followed by Parkinson disease. Anti-cholinergic burden was a contributor for multiple patients. Of 142 patients undergoing lumbar puncture, 71% had positive responses and referred to surgery. Compared to NPH patients, mimickers were statistically significantly older with lower Montreal Cognitive Assessment (MoCA) score and worse gait parameters. Overall, 26% of the original patients underwent shunting. Pre-post testing revealed a statistically significant improved MoCA score and gait parameters in those patients who underwent surgery with follow-up.

CONCLUSION

Because the Multidisciplinary NPH Clinic selected only 26% for surgery (corroborating 30% in Bayes theorem), an overwhelming majority of patients with suspected NPH will harbor alternative diagnoses. Identification of contributing/confounding conditions will support the meticulous work-up necessary to appropriately manage patients without NPH while optimizing clinical responses to shunting in correctly diagnosed patients.

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.

EEG Resting-State Networks Responsible for Gait Disturbance Features in Idiopathic Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a neuropsychiatric disease characterized by gait disturbance, cognitive dysfunction, and urinary incontinence that affects a large population of elderly people. These symptoms, especially gait disturbance, can potentially be improved by cerebrospinal fluid (CSF) drainage, which is more effective if performed at an early stage of the disease. However, the neurophysiological mechanisms of these symptoms and their recovery by CSF drainage are poorly understood. In this study, using exact low-resolution brain electromagnetic tomography-independent component analysis (eLORETA-ICA) with electroencephalography (EEG) data, we assessed activities of five EEG resting-state networks (EEG-RSNs) in 58 iNPH patients before and after drainage of CSF by lumbar puncture (CSF tapping). In addition, we assessed correlations of changes in these five EEG-RSNs activities with CSF tapping-induced changes in iNPH symptoms. The results reveal that compared with 80 healthy controls, iNPH patients had significantly decreased activities in the occipital alpha rhythm, visual perception network, and self-referential network before CSF tapping. Furthermore, CSF tapping-induced changes in occipital alpha activity correlated with changes in postural sway and frontal lobe function. Changes in visual perception network activity correlated with changes in gait speed. In addition, changes in memory perception network activity correlated with changes in Parkinsonian gait features. These results indicate a recruitment of cognitive networks in gait control, and involvement of the occipital alpha activity in cognitive dysfunction in iNPH patients. Based on these findings, eLORETA-ICA with EEG data can be considered a noninvasive, useful tool for detection of EEG-RSN activities and for understanding the neurophysiological mechanisms underlying this disease.

Reversible Dementias

As the worldwide prevalence of dementia increases, there is a greater and more urgent need for all health care providers to understand how to evaluate and manage cognitive impairment. Many people presenting with a dementing illness have one or more reversible underlying conditions that worsen prognosis and, if treated, can improve cognitive function. This article reviews the major potentially reversible dementias, including the basic workup and management of each condition.

Preoperative biomarkers in patients with idiopathic normal pressure hydrocephalus showing a favorable shunt surgery outcome

INTRODUCTION

Idiopathic normal pressure hydrocephalus (INPH) is known to be a potentially treatable neurologic condition. The neurocognitive outcomes after surgery, however, have been variable. It is important to define preoperative characteristics of patients that predicts the shunting outcome. We aimed to compare baseline differences between shunt-responsive and unresponsive patients after 1year from surgery in order to identify preoperative predictors showing favorable clinical outcomes.

METHODS

Among 69 candidates, 31 patients with probable INPH completed the study. Patients were divided into two groups, responsive group (n=17) and unresponsive group (n=14), according to the clinical outcomes on INPH grading scale and modified Rankin score (MRS). Preoperative cerebrospinal (CSF) Aß, tau levels, MRI findings, and clinical characteristics were compared between the groups. Correlations between shunt responsiveness and preoperative characteristics were also assessed.

RESULTS

After 1year from shunt, gait problem was the most likely to improve. Shunt-responsive group showed lower CSF p-tau/Aß, fewer lacunes, and higher incidence of disproportionately enlarged subarachnoid space (DESH) signs on MRIs compared to those in unresponsive group. Favorable outcome was related with positive DESH sign and fewer lacunes.

CONCLUSIONS

Our results suggest that biomarkers representing non-INPH related pathology including Alzheimer's disease and small vessel disease might show less favorable clinical outcomes after 1year from surgery.