Noninvasive biomarkers in normal pressure hydrocephalus: evidence for the role of neuroimaging

Evaluation of imaging indicators in differentiating idiopathic normal pressure hydrocephalus from Alzheimer's disease

BACKGROUND

There are currently many imaging indicators for idiopathic normal pressure hydrocephalus (iNPH). However, their diagnostic performance has not been well compared, especially in differentiating iNPH from Alzheimer's disease (AD). This study aimed to evaluate the diagnostic performance of these imaging indicators in differentiating iNPH from AD.

METHODS

We retrospectively collected patients with iNPH from the West China Hospital between June 2016 and December 2023. Age-sex-matched patients with AD and healthy controls (HCs) are included as controls (ChiCTR2300070078, March 2023). Twelve imaging indicators were evaluated on MRI, including disproportionately enlarged subarachnoid space hydrocephalus (DESH), Evans' index (EI), callosal angle, z-EI, temporal horn, dilated Sylvian fissure, focal sulcal dilation, tight high convexity, deep white matter hyperintensities, periventricular hyperintensities, DESH scale, and Simplified Radscale. We analyzed the receiver operating characteristic curves and calculated the sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy.

RESULTS

A total of 46 patients with iNPH (mean age: 73.1 ± 6.5; 35 males), 46 patients with AD (mean age: 73.0 ± 6.6; 35 males), and 46 HCs (mean age: 73.0 ± 5.9; 35 males) were included. The largest area under the receiver operating characteristic curve (AUC) was found in EI (0.93; 95 % CI: 0.89-0.98) and z-EI (0.93; 95 % CI: 0.87-0.98). DESH scale ≥ 6 had the highest specificity (93 %, 43/46).

CONCLUSION

EI and z-EI had the best diagnostic performance in differentiating iNPH from AD. The DESH scale could assist in diagnosing iNPH due to its high specificity.

Exploring causal correlations of inflammatory biomarkers in idiopathic normal-pressure hydrocephalus: insights from bidirectional Mendelian randomization analysis

Background and objective

Neuroinflammatory processes have been identified as playing a crucial role in the pathophysiology of various neurodegenerative diseases, including idiopathic normal-pressure hydrocephalus (iNPH). iNPH, defined as a common disease of cognitive impairment in older adults, poses major challenges for therapeutic interventions owing to the stringent methodological requirements of relevant studies, clinical heterogeneity, unclear etiology, and uncertain diagnostic criteria. This study aims to assess the relationship between circulating inflammatory biomarkers and iNPH risk using bidirectional two-sample Mendelian randomization (MR) combined with meta-analysis.

Methods

In our bidirectional MR study, genetic data from a genome-wide association study (GWAS) involving 1,456 iNPH cases and 409,726 controls of European ancestry were employed. Single-nucleotide polymorphisms (SNPs) associated with exposures served as instrumental variables for estimating the causal relationships between iNPH and 132 types of circulating inflammatory biomarkers from corresponding GWAS data. Causal associations were primarily examined using the inverse variance-weighted method, supplemented by MR-Egger, weighted median, simple mode, and weighted mode analyses. In the results, heterogeneity was assessed using the Cochran Q test. Horizontal pleiotropy was evaluated through the MR-Egger intercept test and the MR pleiotropy residual sum and outliers test. Sensitivity analysis was conducted through leave-one-out analysis. Reverse MR analyses were performed to mitigate bias from reverse causality. Meta-analyses of identical inflammatory biomarkers from both data sources strengthened the findings.

Results

Results indicated a genetically predicted association between Interleukin-16 (IL-16) [OR: 1.228, 95% CI: 1.049-1.439, p = 0.011], TNF-related apoptosis ligand (TRAIL) [OR: 1.111, 95% CI: 1.019-1.210, p = 0.017] and Urokinase-type plasminogen activator (uPA) [OR: 1.303, 95% CI: 1.025-1.658, p = 0.031] and the risk of iNPH. Additionally, changes in human Glial cell line-derived neurotrophic factor (hGDNF) [OR: 1.044, 95% CI: 1.006-1.084, p = 0.023], Matrix metalloproteinase-1 (MMP-1) [OR: 1.058, 95% CI: 1.020, 1.098, p = 0.003] and Interleukin-12p70 (IL-12p70) [OR: 0.897, 95% CI: 0.946-0.997, p = 0.037] levels were identified as possible consequences of iNPH.

Conclusion

Our MR study of inflammatory biomarkers and iNPH, indicated that IL-16, TRAIL, and uPA contribute to iNPH pathogenesis. Furthermore, iNPH may influence the expression of hGDNF, MMP-1, and IL-12p70. Therefore, targeting specific inflammatory biomarkers could be promising strategy for future iNPH treatment and prevention.

CSF Biomarkers Predict Gait Outcomes in Idiopathic Normal Pressure Hydrocephalus

Background and Objectives

The assessment of biomarkers in selecting patients with idiopathic normal pressure hydrocephalus (iNPH) for shunt surgery has been limited to small cohort studies and those with limited follow-up. We assessed the potential for CSF biomarkers in predicting immediate response to CSF tap test (TT) and long-term response after shunt surgery.

Methods

CSF was obtained from patients with iNPH referred for CSF TT after baseline assessment of cognition and gait. CSF neurofilament light (NfL), β-amyloid 42 (Aβ1-42), β-amyloid 40 (Aβ1-40), total tau (tTau), and phosphorylated tau 181 (pTau181) and leucine-rich alpha-2-glycoprotein-1 (LRG1) were measured by ELISA. The ability of these measures to predict immediate improvement following CSF TT and long-term improvement following shunt surgery was compared by univariate and adjusted multivariate regression.

Results

Lower NfL, pTau181, tTau, and Aβ1-40 were individually predictive of long-term improvement in gait outcomes after shunt surgery. A multivariate model of these biomarkers and MRI Evans index, adjusted for age, improved prediction (area under the receiver operating curve 0.76, 95% confidence interval 0.66-0.86). tTau, pTau181, and Aβ1-40 levels were statistically different in those whose gait improved after CSF TT compared with those who did not. Using a multivariate model, combining these markers with Evans index and transependymal flow did not significantly improve prediction of an immediate response to CSF TT.

Discussion

A combination of CSF biomarkers can predict improvement following shunt surgery for iNPH. However, these measures only modestly discriminate responders from nonresponders following CSF TT. The findings further suggest that abnormal CSF biomarkers in nonresponders may represent comorbid neurodegenerative pathology or a predegenerative phase that presents with an iNPH phenotype.

Corticospinal tract abnormalities and ventricular dilatation: A transdiagnostic comparative tractography study

BACKGROUND

Microstructural alterations of corticospinal tract (CST) have been found in idiopathic normal pressure hydrocephalus (iNPH). No study, however, investigated the effect of ventricular dilatation on CST in Progressive Supranuclear Palsy (PSP).

OBJECTIVE

The aim of this study was to investigate CST diffusion profile in a large cohort of PSP patients with and without ventricular dilatation.

METHODS

Twenty-three iNPH patients, 87 PSP patients and 26 controls were enrolled. Evans index (EI) and ventricular volume (VV) were measured in all patients. CST tractography was performed to calculate FA, MD, AxD and RD in six different anatomical regions: medulla oblungata (MO), pons (P), cerebral peduncle (CP), posterior limb of internal capsule (PLIC), corona radiata (CR), subcortical white matter (SWM). ANCOVA was used for comparing CST diffusion profiles between the groups and association between CST microstructural metrics and measures of ventricular dilatation (EI and VV) was assessed.

RESULTS

Thirty-three PSP patients had ventricular dilatation (EI > 0.30, PSP-vd) while 54 PSP patients had normal ventricular system (EI ≤ 0.30, PSP-wvd). iNPH patients had the most marked FA and AxD increase in PLIC and CR of CST followed by PSP-vd, PSP-wvd and controls; RD was altered only in iNPH. A strong correlation was found between CST diffusion metrics and EI or VV.

CONCLUSIONS

Our findings confirm the microstructural changes of CST in iNPH patients and demonstrate for the first time similar alterations in PSP-vd patients, suggesting a crucial role of ventricular dilatation in the mechanical compression of CST.

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.

Systematic volumetric analysis predicts response to CSF drainage and outcome to shunt surgery in idiopathic normal pressure hydrocephalus

OBJECTIVES

Idiopathic normal pressure hydrocephalus (INPH) is a neurodegenerative disorder characterized by excess cerebrospinal fluid (CSF) in the ventricles, which can be diagnosed by invasive CSF drainage test and treated by shunt placement. Here, we aim to investigate the diagnostic and prognostic power of systematic volumetric analysis based on brain structural MRI for INPH.

METHODS

We performed a retrospective study with a cohort of 104 probable INPH patients who underwent CSF drainage tests and another cohort of 41 INPH patients who had shunt placement. High-resolution T1-weighted images of the patients were segmented using an automated pipeline into 283 structures that are grouped into different granularity levels for volumetric analysis. Volumes at multi-granularity levels were used in a recursive feature elimination model to classify CSF drainage responders and non-responders. We then used pre-surgical brain volumes to predict Tinetti and MMSE scores after shunting, based on the least absolute shrinkage and selection operator.

RESULTS

The classification accuracy of differentiating the CSF drainage responders and non-responders increased as the granularity increased. The highest diagnostic accuracy was achieved at the finest segmentation with a sensitivity/specificity/precision/accuracy of 0.89/0.91/0.84/0.90 and an area under the curve of 0.94. The predicted post-surgical neurological scores showed high correlations with the ground truth, with r = 0.80 for Tinetti and r = 0.88 for MMSE. The anatomical features that played important roles in the diagnostic and prognostic tasks were also illustrated.

CONCLUSIONS

We demonstrated that volumetric analysis with fine segmentation could reliably differentiate CSF drainage responders from other INPH-like patients, and it could accurately predict the neurological outcomes after shunting.

KEY POINTS

• We performed a fully automated segmentation of brain MRI at multiple granularity levels for systematic volumetric analysis of idiopathic normal pressure hydrocephalus (INPH) patients. • We were able to differentiate patients that responded to CSF drainage test with an accuracy of 0.90 and area under the curve of 0.94 in a cohort of 104 probable INPH patients, as well as to predict the post-shunt gait and cognitive scores with a coefficient of 0.80 for Tinetti and 0.88 for MMSE. • Feature analysis showed the inferior lateral ventricle, bilateral hippocampus, and orbital cortex are positive indicators of CSF drainage responders, whereas the posterior deep white matter and parietal subcortical white matter were negative predictors.

Dynamic functional networks in idiopathic normal pressure hydrocephalus: Alterations and reversibility by CSF tap test

Idiopathic Normal Pressure Hydrocephalus (iNPH)—the leading cause of reversible dementia in aging—is characterized by ventriculomegaly and gait, cognitive and urinary impairments. Despite its high prevalence estimated at 6% among the elderlies, iNPH remains underdiagnosed and undertreated due to the lack of iNPH‐specific diagnostic markers and limited understanding of pathophysiological mechanisms. INPH diagnosis is also complicated by the frequent occurrence of comorbidities, the most common one being Alzheimer's disease (AD). Here we investigate the resting‐state functional magnetic resonance imaging dynamics of 26 iNPH patients before and after a CSF tap test, and of 48 normal older adults. Alzheimer's pathology was evaluated by CSF biomarkers. We show that the interactions between the default mode, and the executive‐control, salience and attention networks are impaired in iNPH, explain gait and executive disturbances in patients, and are not driven by AD‐pathology. In particular, AD molecular biomarkers are associated with functional changes distinct from iNPH functional alterations. Finally, we demonstrate a partial normalization of brain dynamics 24 hr after a CSF tap test, indicating functional plasticity mechanisms. We conclude that functional changes involving the default mode cross‐network interactions reflect iNPH pathophysiological mechanisms and track treatment response, possibly contributing to iNPH differential diagnosis and better clinical management.

Identification of Normal Pressure Hydrocephalus by Disease-Specific Patterns of Brain Stiffness and Damping Ratio

OBJECTIVES

The aim of this study was to perform a whole-brain analysis of alterations in brain mechanical properties due to normal pressure hydrocephalus (NPH).

MATERIALS AND METHODS

Magnetic resonance elastography (MRE) examinations were performed on 85 participants, including 44 cognitively unimpaired controls, 33 with NPH, and 8 who were amyloid-positive with Alzheimer clinical syndrome. A custom neural network inversion was used to estimate stiffness and damping ratio from patches of displacement data, accounting for edges by training the network to estimate the mechanical properties in the presence of missing data. This learned inversion was first compared with a standard analytical approach in simulation experiments and then applied to the in vivo MRE measurements. The effect of NPH on the mechanical properties was then assessed by voxel-wise modeling of the stiffness and damping ratio maps. Finally, a pattern analysis was performed on each individual's mechanical property maps by computing the correlation between each person's maps with the expected NPH effect. These features were used to fit a classifier and assess diagnostic accuracy.

RESULTS

The voxel-wise analysis of the in vivo mechanical property maps revealed a unique pattern in participants with NPH, including a concentric pattern of stiffening near the dural surface and softening near the ventricles, as well as decreased damping ratio predominantly in superior regions of the white matter (family-wise error corrected P < 0.05 at cluster level). The pattern of viscoelastic changes in each participant predicted NPH status in this cohort, separating participants with NPH from the control and the amyloid-positive with Alzheimer clinical syndrome groups, with areas under the receiver operating characteristic curve of 0.999 and 1, respectively.

CONCLUSIONS

This study provides motivation for further development of the neural network inversion framework and demonstrates the potential of MRE as a novel tool to diagnose NPH and provide a window into its pathogenesis.

Neural circuits of idiopathic Normal Pressure Hydrocephalus: A perspective review of brain connectivity and symptoms meta-analysis

Idiopathic normal pressure hydrocephalus (iNPH) is a prevalent reversible neurological disorder characterized by impaired locomotion, cognition and urinary control with ventriculomegaly. Symptoms can be relieved with cerebrospinal fluid drainage, which makes iNPH the leading cause of reversible dementia. Because of a limited understanding of pathophysiological mechanisms, unspecific symptoms and the high prevalence of comorbidity (i.e. Alzheimer's disease), iNPH is largely underdiagnosed. For these reasons, there is an urgent need for developing noninvasive quantitative biomarkers for iNPH diagnosis and prognosis. Structural and functional changes of brain circuits in relation to symptoms and treatment response are expected to deliver major advances in this direction. We review structural and functional brain connectivity findings in iNPH and complement those findings with iNPH symptom meta-analyses in healthy populations. Our goal is to reinforce our conceptualization of iNPH as to brain network mechanisms and foster the development of new hypotheses for future research and treatment options.

Impact of timing of ventriculoperitoneal shunt placement on outcome in posttraumatic hydrocephalus

OBJECTIVE

Posttraumatic hydrocephalus (PTH) is a frequent sequela of traumatic brain injury (TBI) and complication of related cranial surgery. The roles of PTH and the timing of cerebrospinal fluid (CSF) shunt placement in TBI outcome have not been well described. The goal of this study was to assess the impact of hydrocephalus and timing of ventriculoperitoneal (VP) shunt placement on outcome during inpatient rehabilitation after TBI.

METHODS

In this cohort study, all TBI patients admitted to Craig Hospital between 2009 and 2013 were evaluated for PTH, defined as ventriculomegaly, and hydrocephalus symptoms, delayed or deteriorating recovery, or elevated opening pressure on lumbar puncture. Extent of ventriculomegaly was quantified by the Evans index from CT scans. Outcome measures were emergence from and duration of posttraumatic amnesia (PTA) and functional status as assessed by means of the Functional Independence Measure (FIM). Findings in this group were compared to findings in a group of TBI patients without PTH (controls) who were admitted for inpatient rehabilitation during the same study period and met specific criteria for inclusion.

RESULTS

A total of 701 patients were admitted with TBI during the study period. Of these patients, 59 (8%) were diagnosed with PTH and were included in this study as the PTH group, and 204 who were admitted for rehabilitation and met the criteria for inclusion as controls constituted the comparison group (no-PTH group). PTH was associated with initial postinjury failure to follow commands, midline shift or cistern compression, subcortical contusion, and craniotomy or craniectomy. In multivariable analyses, independent predictors of longer PTA duration and lower FIM score at rehabilitation discharge were PTH, emergency department Glasgow Coma Scale motor score < 6, and longer time from injury to rehabilitation admission. PTH accounted for a 51-day increase in PTA duration and a 29-point reduction in discharge FIM score. In 40% of PTH patients with preshunt CT brain imaging analyzed, ventriculomegaly (Evans index > 0.3) was observed 3 or more days before VP shunt placement (median 10 days, range 3-102 days). Among PTH patients who received a VP shunt, earlier placement was associated with better outcome by all measures assessed and independently predicted better FIM total score and shorter PTA duration.

CONCLUSIONS

Posttraumatic hydrocephalus predicts worse outcome during inpatient rehabilitation, with poorer functional outcomes and longer duration of PTA. In shunt-treated PTH patients, earlier CSF shunting predicted improved recovery. These results suggest that clinical vigilance for PTH onset and additional studies on timing of CSF diversion are warranted.

Abnormal Gray Matter Structural Networks in Idiopathic Normal Pressure Hydrocephalus

Purpose: Idiopathic normal pressure hydrocephalus (iNPH) is known as a treatable form of dementia. Network analysis is emerging as a useful method to study neurological disorder diseases. No study has examined changes of structural brain networks of iNPH patients. We aimed to investigate alterations in the gray matter (GM) structural network of iNPH patients compared with normal elderly volunteers.

Materials and Methods: Structural networks were reconstructed using covariance between regional GM volumes extracted from three-dimensional T1-weighted images of 29 possible iNPH patients and 30 demographically similar normal-control (NC) participants and compared with each other.

Results: Global network modularity was significantly larger in the iNPH network (P < 0.05). Global network measures were not significantly different between the two networks (P > 0.05). Regional network analysis demonstrated eight nodes with significantly decreased betweenness located in the bilateral frontal, right temporal, right insula and right posterior cingulate regions, whereas only the left anterior cingulate was detected with significantly larger betweenness. The hubs of the iNPH network were mostly located in temporal areas and the limbic lobe, those of the NC network were mainly located in frontal areas.

Conclusions: Network analysis was a promising method to study iNPH. Increased network modularity of the iNPH group was detected here, and modularity analysis should be paid much attention to explore the biomarker to select shunting-responsive patients.

Diffusional Kurtosis along the Corticospinal Tract in Adult Normal Pressure Hydrocephalus

BACKGROUND AND PURPOSE

Normal Pressure Hydrocephalus is a reversible form of dementia characterized by enlarged ventricles, which can deform and cause disruptions to adjacent white matter fibers. The purpose of this work was to examine how diffusion and kurtosis parameters vary along the corticospinal tract and determine where along this path microstructure is compromised in patients diagnosed with normal pressure hydrocephalus. We hypothesized that disruption of the corticospinal tract from ventricular enlargement can be measured using diffusion MR imaging and this will be quantified in periventricular regions.

MATERIALS AND METHODS

We developed a method to analyze diffusion parameters at discrete points along neural tracts. We then used diffusion MR imaging data from patients with Alzheimer disease and healthy controls to compare whether diffusion along the corticospinal tract differs from that of patients with normal pressure hydrocephalus.

RESULTS

We found that diffusion parameters can differentiate patients with normal pressure hydrocephalus from those with Alzheimer disease and healthy controls: Axial diffusion, axial kurtosis, and the axonal water fraction were found to differ significantly across groups (P < .05) in an area located close to the superior internal capsule and corona radiata but below the cortex.

CONCLUSIONS

A lower axonal water fraction indicates a lower axonal density in the corticospinal tract, which may indicate permanent damage. Lower axial kurtosis may imply that axons are being more aligned due to compression.

Lumbar Puncture Test in Normal Pressure Hydrocephalus: Does the Volume of CSF Removed Affect the Response to Tap?

BACKGROUND AND PURPOSE

There is limited evidence to support the use of high-volume lumbar taps over lower-volume taps in the diagnosis of normal pressure hydrocephalus. The purpose of this study is to detect whether the volume of CSF removed from patients undergoing high-volume diagnostic lumbar tap test for normal pressure hydrocephalus is significantly associated with post-lumbar tap gait performance.

MATERIALS AND METHODS

This retrospective study included 249 consecutive patients who underwent evaluation for normal pressure hydrocephalus. The patients were analyzed both in their entirety and as subgroups that showed robust response to the lumbar tap test. The volume of CSF removed was treated as both a continuous variable and a discrete variable. Statistical tests were repeated with log-normalized volumes.

RESULTS

This study found no evidence of a relationship between the volume of CSF removed during the lumbar tap test and subsequent gait test performance in the patient population (Pearson coefficient r = 0.049-0.129). Log normalization of the volume of CSF removed and controlling for age and sex failed to yield a significant relationship. Subgroup analyses focusing on patients who showed greater than 20% improvement in any of the gait end points or who were deemed sufficiently responsive clinically to warrant surgery also yielded no significant relationships between the volume of CSF removed and gait outcomes, but there were preliminary findings that patients who underwent tap with larger-gauge needles had better postprocedure ambulation among patients who showed greater than 20% improvement in immediate time score (P = .04, n = 62).

CONCLUSIONS

We found no evidence to support that a higher volume of CSF removal impacts gait testing, suggesting that a high volume of CSF removal may not be necessary in a diagnostic lumbar tap test.

Diagnosis of Normal-Pressure Hydrocephalus: Use of Traditional Measures in the Era of Volumetric MR Imaging

Purpose To assess the diagnostic performance of the callosal angle (CA) and Evans index (EI) measures and to determine their role versus automated volumetric methods in clinical radiology. Materials and Methods Magnetic resonance (MR) examinations performed before surgery (within 1-5 months of the MR examination) in 36 shunt-responsive patients with normal-pressure hydrocephalus (NPH; mean age, 75 years; age range, 58-87 years; 26 men, 10 women) and MR examinations of age- and sex-matched patients with Alzheimer disease (n = 34) and healthy control volunteers (n = 36) were studied. Three blinded observers independently measured EI and CA for each patient. Volumetric segmentation of global gray matter, white matter, ventricles, and hippocampi was performed by using software. These measures were tested by using multivariable logistic regression models to determine which combination of metrics is most accurate in diagnosis. Results The model that used CA and EI demonstrated 89.6%-93.4% accuracy and average area under the curve of 0.96 in differentiating patients with NPH from patients without NPH (ie, Alzheimer disease and healthy control). The regression model that used volumetric predictors of gray matter and white matter was 94.3% accurate. Conclusion CA and EI may serve as a screening tool to help the radiologist differentiate patients with NPH from patients without NPH, which would allow for designation of patients for further volumetric assessment. ^© RSNA, 2017.

Revisiting secondary normal pressure hydrocephalus: does it exist? A review

OBJECTIVE There are several etiologies that can lead to the development of secondary normal pressure hydrocephalus (sNPH). The aim of this study was to evaluate the etiology, diagnosis, treatment, and outcome in patients with sNPH and to highlight important differences between the separate etiologies. METHODS A comprehensive review of the literature was performed to identify studies conducted between 1965 and 2015 that included data regarding the etiology, treatment, diagnosis, and outcome in patients with sNPH. Sixty-four studies with a total of 1309 patients were included. The inclusion criteria of this study were articles that were written in English, included more than 2 patients with the diagnosis of sNPH, and contained data regarding the etiology, diagnosis, treatment, or outcome of NPH. The most common assessment of clinical improvement was based on the Stein and Langfitt grading scale or equivalent improvement on other alternative ordinal grading scales. RESULTS The main etiologies of sNPH were subarachnoid hemorrhage (SAH) in 46.5%, head trauma in 29%, intracranial malignancies in 6.2%, meningoencephalitis in 5%, and cerebrovascular disease in 4.5% of patients. In 71.9% of patients the sNPH was treated with ventriculoperitoneal shunt placement, and 24.4% had placement of a ventriculoatrial shunt. Clinical improvement after shunt placement was reported in 74.4% and excellent clinical improvement in 58% of patients with sNPH. The mean follow-up period after shunt placement was 13 months. Improvement was seen in 84.2% of patients with SAH, 83% of patients with head trauma, 86.4% of patients with brain tumors, 75% of patients with meningoencephalitis, and 64.7% of patients with NPH secondary to stroke. CONCLUSIONS Secondary NPH encompasses a diverse group of clinical manifestations associated with a subset of patients with acquired hydrocephalus. The most common etiologies of sNPH include SAH and traumatic brain injury. Secondary NPH does indeed exist, and should be differentiated from idiopathic NPH based on outcome and on clinical, pathophysiological, and epidemiological characteristics, but should not be considered as a separate entity.

Multimodal analysis to predict shunt surgery outcome of 284 patients with suspected idiopathic normal pressure hydrocephalus

OBJECTIVES

Optimal selection of idiopathic normal pressure hydrocephalus (iNPH) patients for shunt surgery is challenging. Disease State Index (DSI) is a statistical method that merges multimodal data to assist clinical decision-making. It has previously been shown to be useful in predicting progression in mild cognitive impairment and differentiating Alzheimer's disease (AD) and frontotemporal dementia. In this study, we use the DSI method to predict shunt surgery response for patients with iNPH.

METHODS

In this retrospective cohort study, a total of 284 patients (230 shunt responders and 54 non-responders) from the Kuopio NPH registry were analyzed with the DSI. Analysis included data from patients' memory disorder assessments, age, clinical symptoms, comorbidities, medications, frontal cortical biopsy, CT/MRI imaging (visual scoring of disproportion between Sylvian and suprasylvian subarachnoid spaces, atrophy of medial temporal lobe, superior medial subarachnoid spaces), APOE genotyping, CSF AD biomarkers, and intracranial pressure.

RESULTS

Our analysis showed that shunt responders cannot be differentiated from non-responders reliably even with the large dataset available (AUC = 0.58).

CONCLUSIONS

Prediction of the treatment response in iNPH is challenging even with our extensive dataset and refined analysis. Further research of biomarkers and indicators predicting shunt responsiveness is still needed.

Quantitative evaluation of changes in gait after extended cerebrospinal fluid drainage for normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is characterized by gait instability, urinary incontinence and cognitive dysfunction. These symptoms can be relieved by cerebrospinal fluid (CSF) drainage, but the time course and nature of the improvements are poorly characterized. Attempts to prospectively identify iNPH patients responsive to CSF drainage by evaluating presenting gait quality or via extended lumbar cerebrospinal fluid drainage (eLCD) trials are common, but the reliability of such approaches is unclear. Here we combine eLCD trials with computerized quantitative gait measurements to predict shunt responsiveness in patients undergoing evaluation for possible iNPH. In this prospective cohort study, 50 patients presenting with enlarged cerebral ventricles and gait, urinary, and/or cognitive difficulties were evaluated for iNPH using a computerized gait analysis system during a 3day trial of eLCD. Gait speed, stride length, cadence, and the Timed Up and Go test were quantified before and during eLCD. Qualitative assessments of incontinence and cognition were obtained throughout the eLCD trial. Patients who improved after eLCD underwent ventriculoperitoneal shunt placement, and symptoms were reassessed serially over the next 3 to 15months. There was no significant difference in presenting gait characteristics between patients who improved after drainage and those who did not. Gait improvement was not observed until 2 or more days of continuous drainage in most cases. Symptoms improved after eLCD in 60% of patients, and all patients who improved after eLCD also improved after shunt placement. The degree of improvement after eLCD correlated closely with that observed after shunt placement.

Relationship between cerebrospinal fluid flow, ventricles morphology, and DTI properties in internal capsules: differences between Alzheimer's disease and normal-pressure hydrocephalus

BACKGROUND

Normal-pressure hydrocephalus (NPH) and Alzheimer's disease (AD) have some similar clinical features and both involve white matter and cerebrospinal fluid (CSF) disorders.

PURPOSE

To compare putative relationships between ventricular morphology, CSF flow, and white matter diffusion in AD and NPH.

MATERIAL AND METHODS

Thirty patients (18 with AD and 12 with suspected NPH) were included in the study. All patients underwent a 3-Tesla MRI scan, which included phase-contrast MRI of the aqueduct (to assess the aqueductal CSF stroke volume) and a DTI session (to calculate the fractional anisotropy [FA] and apparent diffusion coefficient [ADC]) in the internal capsules).

RESULTS

FA was correlated with ventricular volume in the suspected NPH population (P < 0.001; rs = 0.88), whereas the ADC was highly correlated with the aqueductal CSF stroke volume in AD (P < 0.001; rs = 0.79).

CONCLUSION

Although AD and NPH both involve CSF disorders, the two diseases do not have the same impact on the internal capsules. The magnitude of the ADC is related to the aqueductal CSF stroke volume in AD, whereas FA is related to ventricular volume in NPH.

Differentiating shunt-responsive normal pressure hydrocephalus from Alzheimer disease and normal aging: pilot study using automated MRI brain tissue segmentation

Evidence suggests that normal pressure hydrocephalus (NPH) is underdiagnosed in day to day radiologic practice, and differentiating NPH from cerebral atrophy due to other neurodegenerative diseases and normal aging remains a challenge. To better characterize NPH, we test the hypothesis that a prediction model based on automated MRI brain tissue segmentation can help differentiate shunt-responsive NPH patients from cerebral atrophy due to Alzheimer disease (AD) and normal aging. Brain segmentation into gray and white matter (GM, WM), and intracranial cerebrospinal fluid was derived from pre-shunt T1-weighted MRI of 15 shunt-responsive NPH patients (9 men, 72.6 ± 8.0 years-old), 17 AD patients (10 men, 72.1 ± 11.0 years-old) chosen as a representative of cerebral atrophy in this age group; and 18 matched healthy elderly controls (HC, 7 men, 69.7 ± 7.0 years old). A multinomial prediction model was generated based on brain tissue volume distributions. GM decrease of 33% relative to HC characterized AD (P < 0.005). High preoperative ventricular and near normal GM volumes characterized NPH. A multinomial regression model based on gender, GM and ventricular volume had 96.3% accuracy differentiating NPH from AD and HC. In conclusion, automated MRI brain tissue segmentation differentiates shunt-responsive NPH with high accuracy from atrophy due to AD and normal aging. This method may improve diagnosis of NPH and improve our ability to distinguish normal from pathologic aging.

The influence of lumbar spinal drainage on diffusion parameters in patients with suspected normal pressure hydrocephalus using 3T MRI

BACKGROUND

Normal pressure hydrocephalus (NPH) has been an ongoing and challenging field of research for the past decades because two main issues are still not fully understood: the pathophysiologic mechanisms underlying ventricular enlargement and prediction of outcome after surgery.

PURPOSE

To evaluate changes in diffusion tensor imaging (DTI) derived parameters in patients with suspected normal pressure hydrocephalus before and after withdrawal of cerebrospinal fluid (CSF).

MATERIAL AND METHODS

Twenty-four consecutive patients with clinical and radiological suspicion of NPH and 14 age-matched control subjects were examined with DTI on a clinical 3T scanner. Patients were examined before and 6-36 h after CSF drainage (interval between scans, 5 days). Fifteen patients were finally included in data analysis. Fractional anisotropy (FA) and mean, parallel, and radial diffusivity (MD, PD, RD) were evaluated using a combination of a ROI-based approach and a whole-brain voxel-by-voxel analysis.

RESULTS

Alteration of DTI parameters in patients with suspected NPH is regionally different. Compared to the control group, we found an elevation of FA in the subcortical white matter (SCWM) and corpus callosum, whereas the other diffusion parameters showed an increase throughout the brain in variable extent. We also found a slight normalization of RD in the SCWM in patients after lumbar drainage.

CONCLUSION

Our results show that DWI parameters are regionally dependent and reflect multifactorial (patho-) physiological mechanisms, which need to be interpreted carefully. It seems that improvement of gait is caused by a decrease of interstitial water deposition in the SCWM.

Long-term hydrocephalus alters the cytoarchitecture of the adult subventricular zone

Hydrocephalus can develop secondarily to a disturbance in production, flow and/or absorption of cerebrospinal fluid. Experimental models of hydrocephalus, especially subacute and chronic hydrocephalus, are few and limited, and the effects of hydrocephalus on the subventricular zone are unclear. The aim of this study was to analyze the effects of long-term obstructive hydrocephalus on the subventricular zone, which is the neurogenic niche lining the lateral ventricles. We developed a new method to induce hydrocephalus by obstructing the aqueduct of Sylvius in the mouse brain, thus simulating aqueductal stenosis in humans. In 120-day-old rodents (n=18 per group), the degree of ventricular dilatation and cellular composition of the subventricular zone were studied by immunofluorescence and transmission electron microscopy. In adult patients (age>18years), the sizes of the subventricular zone, corpus callosum, and internal capsule were analyzed by magnetic resonance images obtained from patients with and without aqueductal stenosis (n=25 per group). Mice with 60-day hydrocephalus had a reduced number of Ki67+ and doublecortin+cells on immunofluorescence, as well as decreased number of neural progenitors and neuroblasts in the subventricular zone on electron microscopy analysis as compared to non-hydrocephalic mice. Remarkably, a number of extracellular matrix structures (fractones) contacting the ventricular lumen and blood vessels were also observed around the subventricular zone in mice with hydrocephalus. In humans, the widths of the subventricular zone, corpus callosum, and internal capsule in patients with aqueductal stenosis were significantly smaller than age and gender-matched patients without aqueductal stenosis. In summary, supratentorial hydrocephalus reduces the proliferation rate of neural progenitors and modifies the cytoarchitecture and extracellular matrix compounds of the subventricular zone. In humans, this similar process reduces the subventricular niche as well as the width of corpus callosum and internal capsule.

The callosal angle measured on MRI as a predictor of outcome in idiopathic normal-pressure hydrocephalus

OBJECT

Different neuroimaging biomarkers have been studied to find a tool for prediction of response to CSF shunting in idiopathic normal-pressure hydrocephalus (iNPH). The callosal angle (CA) has been described as useful in discriminating iNPH from ventricular dilation secondary to atrophy. However, the usefulness of the CA as a prognostic tool for the selection of shunt candidates among patients with iNPH is unclear. The aim of this study was to compare the CA in shunt responders with that in nonresponders and clarify whether the CA can serve as a predictor of the outcome.

METHODS

Preoperative MRI brain scans were evaluated in 109 patients who had undergone shunt surgery for iNPH during 2006-2010. Multiplanar reconstruction was performed interactively to obtain a coronal image through the posterior commissure, perpendicular to the anterior-posterior commissure plane. The CA was measured as the angle between the lateral ventricles on the coronal image. The patients were examined clinically before surgery and at 12 months postoperatively.

RESULTS

Shunt responders had a significantly smaller mean preoperative CA compared with nonresponders: 59° (95% CI 56°-63°) versus 68° (95% CI 61°-75°) (p < 0.05). A CA cutoff value of 63° showed the best prognostic accuracy.

CONCLUSIONS

The preoperative CA is smaller in patients whose condition improves after shunt surgery and may be a useful tool in the selection of shunt candidates among patients with iNPH.

Diffusion tensor imaging of idiopathic normal pressure hydrocephalus: a voxel-based fractional anisotropy study

Diffusion tensor imaging (DTI) using a 3.0 tesla magnetic resonance scanner was used to investigate white matter changes caused by idiopathic normal pressure hydrocephalus (INPH) in 10 patients diagnosed by clinical symptoms (gait disturbance, dementia, and/or urinary incontinence) and Evans index >0.3, and compared with findings for 10 age-matched controls (≥60 years). Then, using a computer-automated method, fractional anisotropy (FA) brain maps were generated and finally transformed into the standard space. Voxel-based FA values within two regions of interests (ROIs), the forceps minor and corticospinal tracts, were then separately evaluated. Within each ROI, statistical comparisons of results from the INPH and control groups were performed. In addition, for INPH patients, grading scores for clinical symptoms and FA values were correlated. The forceps minor mean FA value was much smaller for the INPH group (0.504) than for the control group (0.631). The corticospinal tract mean FA value was slightly smaller for the INPH group (0.588) than for the control group (0.632). Additional analyses indicated that lower FA values within the forceps minor tended to be associated with clinical symptoms such as urinary incontinence and gait disturbance. Our findings indicate FA values decreased in the forceps minor of INPH patients. We also found that lower values were associated with severer clinical symptoms, implying that DTI techniques may be developed for more accurate diagnosis.

The human frontal lobes and frontal network systems: an evolutionary, clinical, and treatment perspective

Frontal lobe syndromes, better termed as frontal network systems, are relatively unique in that they may manifest from almost any brain region, due to their widespread connectivity. The understandings of the manifold expressions seen clinically are helped by considering evolutionary origins, the contribution of the state-dependent ascending monoaminergic neurotransmitter systems, and cerebral connectivity. Hence, the so-called networktopathies may be a better term for the syndromes encountered clinically. An increasing array of metric tests are becoming available that complement that long standing history of qualitative bedside assessments pioneered by Alexander Luria, for example. An understanding of the vast panoply of frontal systems' syndromes has been pivotal in understanding and diagnosing the most common dementia syndrome under the age of 60, for example, frontotemporal lobe degeneration. New treatment options are also progressively becoming available, with recent evidence of dopaminergic augmentation, for example, being helpful in traumatic brain injury. The latter include not only psychopharmacological options but also device-based therapies including mirror visual feedback therapy.

Evans' index revisited: the need for an alternative in normal pressure hydrocephalus

BACKGROUND

The international guidelines for the diagnosis of normal pressure hydrocephalus (NPH) define ventricular enlargement as Evans' index greater than 0.3.

OBJECTIVE

To establish whether there is a correlation between Evans' index and ventricular volume (VV) in NPH and whether choosing different planes for the measurements could produce significantly different results.

METHODS

Pre-shunt insertion, thin-section CT scans of the brains of 10 patients with shunt-responsive NPH were reviewed retrospectively, measuring Evans' index, frontal horn index, VV, and total intracranial volume (ICV). The ventricular/intracranial volume index (VV/ICV) was calculated. Correlation between each of the linear indices and VV and VV/ICV was done.

RESULTS

Significant differences were found in the index values calculated at different planes. The frontal horn index at a plane 16 mm parallel to the anterior commissure-posterior commissure (AC-PC) plane showed best correlation with VV and VV/ICV (r: 0.658 and 0.587, respectively). Evans' index, also obtained at a plane 16 mm parallel to the AC-PC plane, showed best correlation with VV and VV/ICV (r: 0.619 and 0.498, respectively).

CONCLUSION

Evans' index value can vary significantly in a patient with NPH, depending on the level of the brain CT scan image at which the frontal horns and maximal inner skull diameters are measured. Evans' index is not an ideal method for estimating the VV in NPH patients. Volumetric measurements represent the logical accurate estimate of true ventricular size as well as the size of the other intracranial compartments.

Secondary normal pressure hydrocephalus in a patient with isolated frontal dilatation--an insight into pathophysiology?

Current theories of the pathophysiology of normal pressure hydrocephalus suggest the classical symptoms are a consequence of disruption of normal frontal function. We present the case of a 70-year-old patient with an isolated, frontal dilatation of his lateral ventricles in the presence of a complete triad as supportive of these theories.

Diffusion tensor imaging findings in young children with benign external hydrocephalus differ from the normal population

PURPOSE

To compare a pediatric population diagnosed with benign external hydrocephalus (BEH) to normal age-matched controls using diffusion tensor imaging (DTI) techniques.

METHODS

We retrospectively identified 17 BEH patients by specific clinical and neuroimaging criteria. Fractional anisotropy (FA) and mean diffusivity (MD) values obtained from DTI scans were compared to a population of age-matched controls and group differences were examined by mixed model analysis. A longitudinal comparison was completed on a subset that underwent multiple scans (n = 8).

RESULTS

In the genu of the corpus callosum (gCC), six of 15 BEH children had an FA value above the upper limit of 95% prediction interval, nine of 15 BEH children had MD values below the lower limit of 95% prediction interval. A similar trend applied to the other regions of interest (ROIs): splenium of the corpus callosum (sCC), ALIC, and PLIC. Statistical analysis demonstrated significant differences in FA within the gCC, sCC, and PLIC and in MD within the sCC between BEH patients and controls given (P = 0.05). No statistical differences were identified at any ROIs at the later scans.

CONCLUSIONS

We found a significant increase in FA and decrease in MD in children with BEH compared with normal children in specific white matter (WM) ROIs, notably in the gCC and sCC; furthermore, in longitudinal comparison, DTI parameters normalized over time. The current study further demonstrates the ability of DTI to distinguish between subtle diffusion changes in periventricular white matter and establishes preliminary objective radiographic parameters for watchful observation of patients with BEH.

The differential diagnosis and treatment of normal-pressure hydrocephalus

BACKGROUND

Normal-pressure hydrocephalus (NPH) arises in adulthood and is characterized by a typical combination of clinical and radiological findings. The mean basal intracranial pressure is normal or mildly elevated. The typical signs of the disease are gait impairment, urinary incontinence, and dementia. The difficulty of distinguishing NPH from other neurodegenerative disorders is the likely reason why some 80% of cases remain unrecognized and untreated. According to current evidence, the spontaneous course of NPH ends, for the vast majority of patients, in dependence on nursing care.

METHODS

This review article is based on relevant publications retrieved by a selective search in Medline and on national and international guidelines for the management of NPH.

RESULTS

Studies with a high evidence level are lacking; thus, the current state of knowledge about NPH is derived from studies of low or intermediate evidence levels, e.g., observational studies. Modern forms of treatment lead to clinical improvement in 70% to 90% of treated patients. The treatment of choice is the implantation of a ventriculoperitoneal shunt. The differential diagnosis is complicated by the fact that three-quarters of patients with NPH severe enough to require treatment also suffer from another neurodegenerative disorder. Therefore, the clinical findings and imaging studies often do not suffice to establish the indication for surgery. To do this, a further, semi-invasive diagnostic procedure is recommended. Current risk/benefit analyses indicate that shunt operations improve outcome compared to the spontaneous course of the disease.

CONCLUSION

Normal pressure hydrocephalus should always enter into the differential diagnosis of patients who present with its characteristic manifestations. If the diagnosis of NPH is confirmed, it should be treated at an early stage.

Correlating magnetic resonance findings with neuropathology and clinical signs in dogs and cats

The histologic characteristics that are the basis for diagnosis of central nervous system conditions cannot be visualized directly using magnetic resonance (MR) methods, but clinical diagnosis may be based on the frequency and pattern of MR imaging signs, which represent predominantly the gross morphologic features of lesions. Additional quantitative MR measures of myelination, cell swelling, gliosis, and neuronal loss may also be used for more specific characterization of lesions. These measures include magnetization transfer ratio, apparent diffusion coefficient, and the concentrations or ratios of metabolites identified by spectroscopy. Confidence that an MR abnormality is responsible for the clinical signs depends primarily on the degree of correspondence between the site of the lesion and the neuroanatomical localization.

Cognitive, biochemical, and imaging profile of patients suffering from idiopathic normal pressure hydrocephalus

INTRODUCTION

It has still not been clearly established whether the cognitive deficits of idiopathic normal pressure hydrocephalus (iNPH) are caused by a disturbance in cerebrospinal fluid (CSF) dynamics or an underlying metabolic disturbance.

OBJECTIVE

To identify the possible associations between biochemical markers, the neuroimaging characteristics, and cognitive deficits of patients undergoing investigations for possible iNPH.

METHODS

A CSF sample obtained during a lumbar puncture from 10 patients with iNPH was analyzed for several biochemical markers (lactate, 8-isoprostane, vascular endothelial growth factor [VEGF], neurofilament heavy protein, glial fibrillary acidic protein, amyloid beta 1-42, and total tau). All patients underwent a battery of neuropsychological testing and imaging as part of their selection process for their suitability for CSF diversion surgical procedure. Volumetric analysis of imaging was carried out measuring the ventricular volume (VV), intracranial volume (ICV), periventricular lucencies, deep white matter hyperintensities, and white matter (WM) volume, as well as their ratios.

RESULTS

A significant negative correlation of preoperative symptom duration and total tau levels (R = -0.841, P = .002) was found. There was a significant positive correlation (R = 0.648, P = .043) between the levels of VEGF and the VV/ICV ratio. There was a significant positive correlation of the levels of glial fibrillary acidic protein and the VV/deep white matter hyperintensities ratio (R = 0.828, P = .006). A significant negative correlation was observed between the levels of neurofilament heavy protein and the VV/ICV ratio (R = -0.657, P = .039) and the WM volume (R = -0.778, P = .023). Lactate levels were lower for patients performing in the normal range on the Recognition Memory Test for faces. Patients who performed better in the Recognition Memory Test words test had higher ICV volumes. All the patients in this study showed below normal performance when the subcortical function was assessed.

CONCLUSION

The positive correlation of VEGF with the severity of ventriculomegaly may indicate that this is because of the transmantle pressure gradient; this response may not be because of hypoxia but represents an attempt at neuroregeneration. The degree of reactive gliosis correlates inversely with the severity of WM lesions. Neuronal degeneration is negatively correlated with the volume of the WM in these patients. The small association of volumetry and the cognitive profile of these patients may be consistent with a direct biochemical disturbance being responsible for the cognitive deficit observed. Ongoing studies with set protocols for neuropsychological assessment and volumetric analysis are warranted to further elucidate on the preliminary results of the current study.

Differential diagnosis of idiopathic normal pressure hydrocephalus from other dementias using diffusion tensor imaging

BACKGROUND AND PURPOSE

Because DTI can provide good markers of white matter pathology, it could be useful in differentiating white matter changes of INPH from those of other dementias. The aim of this study was, by using DTI, to compare the characteristic white matter changes in INPH with those in AD, subcortical vascular dementia, and healthy control subjects.

MATERIALS AND METHODS

Sixteen patients with presurgical INPH, 10 with AD, 10 with subcortical vascular dementia, and 20 healthy control subjects underwent DTI. All patients with INPH showed clinical improvement after shunt surgery, and 9 of them also underwent postshunting DTI. Regions of interest were selected at the periventricular white matter, the anterior limb of the internal capsule, the posterior limb of the internal capsule, the genu and the splenium of the corpus callosum, the superior longitudinal fasciculus, and the inferior longitudinal fasciculus. FA and MD were obtained from each region of interest and were compared among the groups.

RESULTS

Presurgical INPH showed significantly higher FA than all the other groups in the posterior limb of the internal capsule, which was decreased after shunt surgery. Presurgical MD of the INPH group was higher than that in the AD and healthy control groups but lower than that in the subcortical vascular dementia group in the anterior periventricular white matter, the anterior limb of the internal capsule, and the superior longitudinal fasciculus. In differentiating INPH, the sensitivity and specificity of FA in the posterior limb of the internal capsule was 87.5% and 95.0%, respectively.

CONCLUSIONS

Patients with shunt-responsive INPH showed higher FA in the posterior limb of the internal capsule compared with healthy controls and those in other groups of dementia that was reversible with shunt surgery. With this parameter, shunt-responsive INPH could be distinguished from AD, subcortical vascular dementia, and healthy conditions with high diagnostic accuracy.

The role of the neurologist in the longitudinal management of normal pressure hydrocephalus

BACKGROUND

Since normal pressure hydrocephalus (NPH) was first described in 1965, neurologists have been involved in the initial diagnostic evaluation for it but have rarely followed patients specifically to monitor response to therapy after shunt surgery.

REVIEW SUMMARY

The potential role for the neurologist in the longitudinal management of NPH has broadened, partly because of improvement in the tools used to diagnose and treat NPH and partly because of progress in understanding how NPH mimics and interacts with other common disorders of the elderly. The interplay of Alzheimer dementia, vascular dementia, Parkinson disease, and spinal stenosis with NPH presents the clinician with a patient profile that may be challenging to assess. Neurologists also face a broad differential spectrum of less common neurologic diseases that may present with similar signs (including ventriculomegaly) and symptoms; these diseases include frontotemporal dementia, progressive supranuclear palsy, Lewy body disease, corticobasal degeneration, Huntington disease, spongiform encephalopathy, and multiple-system atrophy.

CONCLUSIONS

The neurologist is in a unique position to differentiate NPH from alternative diagnoses, to suggest management strategies for patients with concomitant NPH and another neurologic disorder, and to participate in longitudinal management of NPH.

Brain MRI as a predictor of CSF tap test response in patients with idiopathic normal pressure hydrocephalus

In this study, our objective was to identify the characteristic morphological features of brain MRI associated with a positive cerebrospinal fluid (CSF) tap test in patients with idiopathic normal pressure hydrocephalus (iNPH). Patients diagnosed with clinical suspected iNPH were evaluated. All patients underwent a mini-mental state examination, a brain MRI, and a CSF tap test. The severities of clinical symptoms were rated before and after the CSF tap test. Characteristic brain MRI findings including frontal convexity narrowing, parietal convexity narrowing, upward bowing of the corpus callosum, empty sella, narrowing of the CSF space at the high convexity, marked dilatation of the Sylvian fissure, and disproportion between narrowing of the CSF space at the high convexity and dilatation of the Sylvian fissure ("mismatch" sign) on T1-weighted or FLAIR image were analyzed. Forty-three patients (33 males/ten females, mean age 76.9 ± 6.9 years) with possible iNPH participated in this study. The presence versus absence of empty sella (52.4 vs. 14.3%, OR 6.6, 95% CI 1.5-29.4, p = 0.02) and "mismatch" sign (45.5 vs. 9.5%, OR 7.9, 95% CI 1.5-42.5, p = 0.02) were associated with positive CSF tap test responses. The sensitivity, specificity, positive predictive value, and negative predictive value of the presence of either of these two MRI features in the prediction of CSF tap response were 72.7, 81, 80, and 73.9%, respectively. Specific brain MRI features can be used as markers for the identification of potential CSF tap test responders in iNPH patients. These features may serve as supplemental evidence in the diagnosis of iNPH patients.

Ongoing search for diagnostic biomarkers in idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus is a syndrome, which typically has a clinical presentation of gait/balance disturbance, often accompanied by cognitive decline and/or urinary incontinence. Its diagnosis is based on relevant history and clinical examination, appropriate imaging findings and physiological testing. The clinical picture of idiopathic normal pressure hydrocephalus may occasionally be difficult to distinguish from that of Alzheimer’s dementia, subcortical ischemic vascular dementia and Parkinson’s disease. The aim of this article is to systematically review the literature from the last 29 years in order to identify cerebrospinal fluid (CSF) or imaging biomarkers that may aid in the diagnosis of the syndrome. The authors concluded that no CSF or imaging biomarker is currently fulfilling the criteria required to aid in the diagnosis of the condition. However, a few studies have revealed promising CSF and imaging markers that need to be verified by independent groups. The reasons that the progress in this field has been slow so far is also commented on, as well as steps required to apply the current evidence in the design of future studies within the field.