Exploring mechanisms of ventricular enlargement in idiopathic normal pressure hydrocephalus: a role of cerebrospinal fluid dynamics and motile cilia

Enlarged choroid plexus is linked with poorer physical function in rural older adults: a population-based study

BACKGROUND

The choroid plexus (ChP) plays an important role in producing cerebrospinal fluid (CSF) and physical dysfunction has been associated with alterations in CSF circulation. However, no population-based studies have thus far examined the association of ChP with physical function in older people.

METHODS

This population-based cross-sectional study included 1217 participants (age ≥ 60 years; 57.35% women) in the MRI substudy of the Multimodal Interventions to delay Dementia and disability in rural China. ChP volume was automatically segmented using three-dimensional T1-weighted sequences. Physical function was assessed using the Short Physical Performance Battery (SPPB). Data were analyzed using general linear regression and mediation models.

RESULTS

Controlling for demographic characteristics, cardiovascular risk factors, stroke, disproportionately enlarged subarachnoid-space hydrocephalus (DESH), and total intracranial volume, per 1-ml increase in ChP volume was associated with β-coefficient of -0.24 (95% confidence interval: -0.37 to -0.11) for SPPB summary score, with the association being stronger in females (-0.40; -0.60 to -0.20) than in males (-0.17; -0.33 to -0.01) (p for ChP volume×sex interaction = 0.028). The associations were similar across three domains of balance, chair stand, and walking speed. In addition, enlarged ChP volume was associated with increased ventricular volume and white matter hyperintensity (WMH) volume. Mediation analysis suggested that lateral ventricular volume and periventricular WMH volume significantly mediated the association of ChP volume with the SPPB summary score, with the proportion of mediation being 54.22% and 14.48%, respectively.

CONCLUSION

Larger ChP volume is associated with poorer physical function in older adults, especially in women. The association is largely mediated by lateral ventricular and periventricular WMH volumes.

Disproportionately Enlarged Subarachnoid-Space Hydrocephalus on MRI in Pathologically Confirmed Progressive Supranuclear Palsy

Background and Objective

Several studies have shown that idiopathic normal-pressure hydrocephalus (iNPH) can mimic other neurodegenerative disorders, particularly progressive supranuclear palsy (PSP). In this study, we investigated iNPH clinical and neuroimaging features in patients with autopsy-confirmed PSP or Lewy body disease (LBD) by assessing the normal pressure hydrocephalus (NPH) triad of symptoms and imaging features of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) and Evans index (EI) on antemortem MRI scans.

Methods

Among our study participants (N = 190), the mean (SD) age was 76.8 (9.2) years and 134 (70.5%) were male. The patients had been followed at Mayo Clinic and had autopsy diagnosis of either PSP or LBD. Patients were excluded if they had Alzheimer disease or a history of a disorder that could cause hydrocephalus, such as chronic meningitis or neoplasia. The study included 101 patients with PSP and 89 with LBD. The frequency of DESH and a high EI on brain MRI were analyzed in PSP and LBD with logistic regression analyses, adjusting for age, sex, and brain weight. The NPH triad of symptoms was assessed relative to imaging findings.

Results

We found that DESH and high EI were similar between PSP and LBD. The mean age at death (PSP: 74.0 [8.2]; LBD: 80.0 [9.2]) and brain weight (PSP: 1,190 [123]; LBD: 1,300 [150]) were greater in LBD compared with PSP (p < 0.001 for each). The frequency of DESH was greater in LBD than PSP (13% vs 3%, p = 0.004), while a high EI was similar in PSP and LBD (36% vs 32%, p = 0.500). The adjusted odds ratios for DESH and high EI were similar between the 2 groups (DESH: adjusted ORs 0.3, 95% CI 0.06-1.25, p = 0.119; high EI: adjusted ORs 1.8, 95% CI 0.86-4.06, p = 0.120).

Discussion

These findings suggest that DESH and high EI, often considered biomarkers for iNPH, may lack specificity and may be found in a subset of patients with PSP or LBD leading to unnecessary neurosurgery for iNPH.

Neuroimaging of Adult Hydrocephalus

Ventricle expansion and disproportionately enlarged subarachnoid-space hydrocephalus (DESH) are the hallmark features of idiopathic normal-pressure hydrocephalus, which has recently also been referred to as Hakim's disease. DESH refers to the unbalanced distribution of CSF in the subarachnoid space characterized by tightened sulci in the high convexities and Sylvian fissure dilation. The ventricles and Sylvian fissure expand in the parietal direction. This process compresses the brain and subarachnoid space around the parietal region. In addition to 2-dimensional imaging indicators, this study describes new 3-dimensional and 4-dimensional imaging indicators.

Neurodevelopmental Implications Underpinning Hereditary Spastic Paraplegia

BACKGROUND

Hereditary spastic paraplegia (HSP) is a group of rare genetic neurodegenerative disorders characterized by corticospinal tract abnormalities. But frequently, abnormalities of proteins implicated in HSP have been identified in brain disorders of childhood, raising the possibility that early brain developmental mechanism underlying HSP.

RESULTS AND CONCLUSIONS

Here we summarized the clinical features of 89 HSP subtypes and found most have onset of symptoms earliest reported in infancy or early childhood. Importantly, HSP patients showed early brain developmental related phenotypes such as microcephaly, ventricular enlargement, and corpus callosum dysplasia. In addition, the expression trajectories analysis showed HSP genes were diffusely expressed across all human prenatal cortical regions and most genes enriched from post-conception weeks 8-24, periods characterized by neuro progenitor proliferation and neurogenesis. Furthermore, studies utilizing patient derived induced pluripotent stem cells (iPSCs)/organoids and mouse models have suggested that most HSP proteins play either direct or indirect roles in the development of the central nervous system. Therefore, HSP possesses a neurodevelopmental aspect and is not merely a degenerative disease, which may aid in better understanding the pathogenesis of this disease.

Screening of Aβ and phosphorylated tau status in the cerebrospinal fluid through machine learning analysis of portable electroencephalography data

Diagnosing Alzheimer's disease (AD) through pathological markers is typically costly and invasive. This study aims to find a noninvasive, cost-effective method using portable electroencephalography (EEG) to detect changes in AD-related biomarkers in cerebrospinal fluid (CSF). A total of 102 patients, both with and without AD-related biomarker changes (amyloid beta and phosphorylated tau), were recorded using a 2-minute resting-state portable EEG. A machine-learning algorithm then analyzed the EEG data to identify these biomarker changes. The results showed that the machine learning model could distinguish patients with AD-related biomarker changes, achieving 68.1% accuracy (AUROC 0.75) for amyloid beta and 71.2% accuracy (AUROC 0.77) for phosphorylated tau, with gamma activities being key features. When excluding cases with idiopathic normal pressure hydrocephalus, accuracy improved to 74.1% (AUROC 0.80) for amyloid beta and 73.1% (AUROC 0.80) for phosphorylated tau. This study suggests that portable EEG combined with machine learning is a promising noninvasive and cost-effective tool for early AD-related pathological marker screening, which could enhance neurophysiological understanding and diagnostic accessibility.

Transmantle pressure under the influence of free breathing: non-invasive quantification of the aqueduct pressure gradient in healthy adults

BACKGROUND

The pressure gradient between the ventricles and the subarachnoid space (transmantle pressure) is crucial for understanding CSF circulation and the pathogenesis of certain neurodegenerative diseases. This pressure can be approximated by the pressure difference across the aqueduct (ΔP). Currently, no dedicated platform exists for quantifying ΔP, and no research has been conducted on the impact of breathing on ΔP. This study aims to develop a post-processing platform that balances accuracy and ease of use to quantify aqueduct resistance and, in combination with real-time phase contrast MRI, quantify ΔP driven by free breathing and cardiac activities.

METHODS

Thirty-four healthy participants underwent 3D balanced fast field echo (BFFE) sequence and real-time phase contrast (RT-PC) imaging on a 3T scanner. We used the developed post-processing platform to analyse the BFFE images to quantify the aqueduct morphological parameters such as resistance. RT-PC data were then processed to quantify peak flow rates driven by cardiac and free breathing activity (Qc and Qb) in both directions. By multiplying these Q by resistance, ΔP driven by cardiac and breathing activity was obtained (ΔPc and ΔPb). The relationships between aqueduct resistance and flow rates and ΔP driven by cardiac and breathing activity were analysed, including a sex difference analysis.

RESULTS

The aqueduct resistance was 78 ± 51 mPa·s/mm³. The peak-to-peak cardiac-driven ΔP (Sum of ΔPc+ and ΔPc-) was 24.2 ± 11.4 Pa, i.e., 0.18 ± 0.09 mmHg. The peak-to-peak breath-driven ΔP was 19 ± 14.4 Pa, i.e., 0.14 ± 0.11 mmHg. Males had a longer aqueduct than females (17.9 ± 3.1 mm vs. 15 ± 2.5 mm, p < 0.01) and a larger average diameter (2.0 ± 0.2 mm vs. 1.8 ± 0.3 mm, p = 0.024), but there was no gender difference in resistance values (p = 0.25). Aqueduct resistance was negatively correlated with stroke volume and the peak cardiac-driven flow (p < 0.05); however, there was no correlation between aqueduct resistance and breath-driven peak flow rate.

CONCLUSIONS

The highly automated post-processing software developed in this study effectively balances ease of use and accuracy for quantifying aqueduct resistance, providing technical support for future research on cerebral circulation physiology and the exploration of new clinical diagnostic methods. By integrating real-time phase contrast MRI, this study is the first to quantify the aqueduct pressure difference under the influence of free breathing. This provides an important physiological reference for further studies on the impact of breathing on transmantle pressure and cerebral circulation mechanisms.

MRI imaging characteristics of brainstem and midbrain aqueduct in patients with iNPH

Idiopathic normal pressure hydrocephalus (iNPH) is frequently difficult to diagnose due to the absence of specific symptoms, yet early detection and surgical intervention are essential for preventing sequela such as irreversible dementia. This study explores the specific magnetic resonance imaging (MRI) features of the brainstem and mesencephalic aqueduct in patients with iNPH. Head MRI data of 50 iNPH patients and 30 healthy matched controls were compared for mesencephalic aqueduct length, diameter, and angle, structural features of the brainstem at the sagittal plane, brainstem component volume ratios, angle between the brainstem and spinal cord, and the area and morphology of the pontine cisterns. Compared to healthy individuals, iNPH patients exhibited significant dilation of the mesencephalic aqueduct diameter, a reduced aqueduct angle, and a decrease in the sagittal plane area of the brainstem, with the most pronounced reduction in the midbrain region. Notably, the CSF spaces surrounding the brainstem were dilated, resulting in the prepontine cistern presenting a "hammer-like" shape on the sagittal plane. The prevalence of this hammer shape was positively correlated with prepontine cistern area in patients with iNPH. These unique imaging characteristics may facilitate the clinical recognition of iNPH for early diagnosis and treatment.

Cardiac and respiratory activities induce temporal changes in cerebral blood volume, balanced by a mirror CSF volume displacement in the spinal canal

Understanding cerebrospinal fluid (CSF) dynamics is crucial for elucidating the pathogenesis and diagnosis of neurodegenerative diseases. The primary mechanisms driving CSF oscillations remain a topic of debate. This study investigates whether cerebral blood volume displacement (CBV), modulated by breathing and cardiac activity, is the predominant drivers of CSF oscillations. We examined 12 healthy volunteers (aged 20-34 years) using a clinical 3T MRI scanner to quantify cerebral blood flow at the intracranial level and CSF flow at the C2-C3 spinal level under free and deep breathing conditions, utilizing real-time phase-contrast sequences. We then obtained CBV and CSF volume displacement (CSFV) curves by integrating the flow rate signals. Cardiac and respiratory signals were recorded during acquisition to reconstruct cardiac-driven and breath-driven CBV and CSFV curves. During deep breathing, compared to free breathing, the total cerebral arterial flow rate decreased by 29 % (from 12.5 ml/s to 8.8 ml/s), and the duration of the cardiac cycle period shortened by 15 % (0.90 s to 0.77 s), leading to reductions of 37 % and 23 % in cardiac-driven CBV and CSFV amplitudes, respectively. Conversely, breath-driven CBV and CSFV amplitudes increased substantially by 207 % and 326 %, respectively. Notably, during free breathing, cardiac-driven CBV and CSFV were significantly greater than their breath-driven counterparts; however, during deep breathing, the amplitudes of cardiac-driven and breath-driven CBV and CSFV did not differ significantly. CBV and CSFV curves demonstrated strong coupled inverse oscillation under both breathing conditions, with consistent CSF inflow toward the intracranial compartment during inspiration. This study quantifies the contributions of cardiac and breathing activities to CBV and CSFV under varying breathing patterns, confirming that CBV changes, driven by cardiac and respiratory activities, are strongly inversely coupled with CSF oscillations. These findings enhance our understanding of CSF circulation mechanisms and offer potential diagnostic implications for neurodegenerative diseases.

Association between telomere length and idiopathic normal pressure hydrocephalus: a Mendelian randomization study

Objective

Idiopathic normal pressure hydrocephalus (iNPH) is highly prevalent among elderly individuals, and there is a strong correlation between telomere length and biological aging. However, there is limited evidence to elucidate the relationship between telomere length and iNPH. This study aimed to investigate the associations between telomere length and iNPH using the Mendelian randomization (MR) method.

Methods

The genetic variants of telomere length were obtained from 472,174 UK Biobank individuals. Summary level data of iNPH were acquired from 218,365 individuals of the FinnGen consortium. Five MR estimation methods, including inverse-variance weighting (IVW), MR-Egger regression, weighted median, weighted mode and simple mode, were used for causal inference. Comprehensive sensitivity analyses were conducted to test the robustness of the results. In addition, multivariable MR was further implemented to identify potential mechanisms in the causal pathway from telomere length to iNPH.

Results

Genetically determined longer telomere length was significantly associated with decreased risk of iNPH (OR = 0.44, 95% CI 0.24-0.80; p = 0.008). No evident heterogeneity (Cochran Q = 138.11, p = 0.386) and pleiotropy (MR Egger intercept = 0.01, p = 0.514) were observed in the sensitivity analysis. In addition, multivariable MR indicated that the observed association was attenuated after adjustment for several vascular risk factors, including essential hypertension (IVW OR = 0.55, 95% CI 0.30-1.03; p = 0.061), type 2 diabetes (IVW OR = 0.71, 95% CI 0.09-5.39; p = 0.740) and coronary artery disease (IVW OR = 0.58, 95% CI 0.31-1.07; p = 0.082).

Conclusion

Our MR study revealed a strong negative correlation of telomere length with iNPH. The causal relationship might be driven by several vascular risk factors.

Mechanisms of hydrocephalus after intraventricular haemorrhage: a review

Intraventricular haemorrhage (IVH) is bleeding within the ventricular system, which in adults is usually mainly secondary to cerebral haemorrhage and subarachnoid haemorrhage. Hydrocephalus is one of the most common complications of intraventricular haemorrhage, which is characterised by an increase in intracranial pressure due to an increased accumulation of cerebrospinal fluid within the ventricular system, and is closely related to the patient's prognosis. Surgical methods such as shunt surgery have been used to treat secondary hydrocephalus in recent years and have been effective in improving the survival and prognosis of patients with hydrocephalus. However, complications such as shunt blockage and intracranial infection are often faced after surgery. Moreover, little is known about the mechanism of hydrocephalus secondary to intraventricular haemorrhage. This review discusses the mechanisms regarding the occurrence of secondary hydrocephalus after intraventricular haemorrhage in adults in terms of blood clot obstruction, altered cerebrospinal fluid dynamics, inflammation, and blood composition.

Impairment of spinal CSF flow precedes immune cell infiltration in an active EAE model

Accumulation of immune cells and proteins in the subarachnoid space (SAS) is found during multiple sclerosis and in the animal model experimental autoimmune encephalomyelitis (EAE). Whether the flow of cerebrospinal fluid (CSF) along the SAS of the spinal cord is impacted is yet unknown. Combining intravital near-infrared (NIR) imaging with histopathological analyses, we observed a significantly impaired bulk flow of CSF tracers within the SAS of the spinal cord prior to EAE onset, which persisted until peak stage and was only partially recovered during chronic disease. The impairment of spinal CSF flow coincided with the appearance of fibrin aggregates in the SAS, however, it preceded immune cell infiltration and breakdown of the glia limitans superficialis. Conversely, cranial CSF efflux to cervical lymph nodes was not altered during the disease course. Our study highlights an early and persistent impairment of spinal CSF flow and suggests it as a sensitive imaging biomarker for pathological changes within the leptomeninges.

Accumulation of Cerebrospinal Fluid, Ventricular Enlargement, and Cerebral Folate Metabolic Errors Unify a Diverse Group of Neuropsychiatric Conditions Affecting Adult Neocortical Functions

Cerebrospinal fluid (CSF) is a fluid critical to brain development, function, and health. It is actively secreted by the choroid plexus, and it emanates from brain tissue due to osmolar exchange and the constant contribution of brain metabolism and astroglial fluid output to interstitial fluid into the ventricles of the brain. CSF acts as a growth medium for the developing cerebral cortex and a source of nutrients and signalling throughout life. Together with perivascular glymphatic and interstitial fluid movement through the brain and into CSF, it also acts to remove toxins and maintain metabolic balance. In this study, we focused on cerebral folate status, measuring CSF concentrations of folate receptor alpha (FOLR1); aldehyde dehydrogenase 1L1, also known as 10-formyl tetrahydrofolate dehydrogenase (ALDH1L1 and FDH); and total folate. These demonstrate the transport of folate from blood across the blood-CSF barrier and into CSF (FOLR1 + folate), and the transport of folate through the primary FDH pathway from CSF into brain FDH + ve astrocytes. Based on our hypothesis that CSF flow, drainage issues, or osmotic forces, resulting in fluid accumulation, would have an associated cerebral folate imbalance, we investigated folate status in CSF from neurological conditions that have a severity association with enlarged ventricles. We found that all the conditions we examined had a folate imbalance, but these folate imbalances were not all the same. Given that folate is essential for key cellular processes, including DNA/RNA synthesis, methylation, nitric oxide, and neurotransmitter synthesis, we conclude that ageing or some form of trauma in life can lead to CSF accumulation and ventricular enlargement and result in a specific folate imbalance/deficiency associated with the specific neurological condition. We believe that addressing cerebral folate imbalance may therefore alleviate many of the underlying deficits and symptoms in these conditions.

Regulation of brain fluid volumes and pressures: basic principles, intracranial hypertension, ventriculomegaly and hydrocephalus

The principles of cerebrospinal fluid (CSF) production, circulation and outflow and regulation of fluid volumes and pressures in the normal brain are summarised. Abnormalities in these aspects in intracranial hypertension, ventriculomegaly and hydrocephalus are discussed. The brain parenchyma has a cellular framework with interstitial fluid (ISF) in the intervening spaces. Framework stress and interstitial fluid pressure (ISFP) combined provide the total stress which, after allowing for gravity, normally equals intracerebral pressure (ICP) with gradients of total stress too small to measure. Fluid pressure may differ from ICP in the parenchyma and collapsed subarachnoid spaces when the parenchyma presses against the meninges. Fluid pressure gradients determine fluid movements. In adults, restricting CSF outflow from subarachnoid spaces produces intracranial hypertension which, when CSF volumes change very little, is called idiopathic intracranial hypertension (iIH). Raised ICP in iIH is accompanied by increased venous sinus pressure, though which is cause and which effect is unclear. In infants with growing skulls, restriction in outflow leads to increased head and CSF volumes. In adults, ventriculomegaly can arise due to cerebral atrophy or, in hydrocephalus, to obstructions to intracranial CSF flow. In non-communicating hydrocephalus, flow through or out of the ventricles is somehow obstructed, whereas in communicating hydrocephalus, the obstruction is somewhere between the cisterna magna and cranial sites of outflow. When normal outflow routes are obstructed, continued CSF production in the ventricles may be partially balanced by outflow through the parenchyma via an oedematous periventricular layer and perivascular spaces. In adults, secondary hydrocephalus with raised ICP results from obvious obstructions to flow. By contrast, with the more subtly obstructed flow seen in normal pressure hydrocephalus (NPH), fluid pressure must be reduced elsewhere, e.g. in some subarachnoid spaces. In idiopathic NPH, where ventriculomegaly is accompanied by gait disturbance, dementia and/or urinary incontinence, the functional deficits can sometimes be reversed by shunting or third ventriculostomy. Parenchymal shrinkage is irreversible in late stage hydrocephalus with cellular framework loss but may not occur in early stages, whether by exclusion of fluid or otherwise. Further studies that are needed to explain the development of hydrocephalus are outlined.

Enlarged perivascular spaces and their association with motor, cognition, MRI markers and cerebrovascular risk factors in male fragile X premutation carriers

FMR1 premutation carriers (55-200 CGG repeats) are at risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS), a neurodegenerative disorder associated with motor and cognitive impairment. Bilateral hyperintensities of the middle cerebellar peduncles (MCP sign) are the major radiological hallmarks of FXTAS. In the general population, enlarged perivascular spaces (PVS) are biomarkers of small vessel disease and glymphatic dysfunction and are associated with cognitive decline. Our aim was to determine if premutation carriers show higher ratings of PVS than controls and whether enlarged PVS are associated with motor and cognitive impairment, MRI features of neurodegeneration, cerebrovascular risk factors and CGG repeat length. We evaluated 655 MRIs (1-10 visits/participant) from 229 carriers (164 with FXTAS and 65 without FXTAS) and 133 controls. PVS in the basal ganglia (BG-EPVS), centrum semiovale, and midbrain were evaluated with a semiquantitative scale. Mixed-effects models were used for statistical analysis adjusting for age. In carriers with FXTAS, we revealed that (1) BG-PVS ratings were higher than those of controls and carriers without FXTAS; (2) BG-PVS severity was associated with brain atrophy, white matter hyperintensities, enlarged ventricles, FXTAS stage and abnormal gait; (3) age-related increase in BG-PVS was associated with cognitive dysfunction; and (4) PVS ratings of all three regions showed robust associations with CGG repeat length and were higher in carriers with the MCP sign than carriers without the sign. This study demonstrates clinical relevance of PVS in FXTAS especially in the basal ganglia region and suggests microangiopathy and dysfunctional cerebrospinal fluid circulation in FXTAS physiopathology.

Modeling cerebrospinal fluid dynamics across the entire intracranial space through integration of four-dimensional flow and intravoxel incoherent motion magnetic resonance imaging

BACKGROUND

Bidirectional reciprocal motion of cerebrospinal fluid (CSF) was quantified using four-dimensional (4D) flow magnetic resonance imaging (MRI) and intravoxel incoherent motion (IVIM) MRI. To estimate various CSF motions in the entire intracranial region, we attempted to integrate the flow parameters calculated using the two MRI sequences. To elucidate how CSF dynamics deteriorate in Hakim's disease, an age-dependent chronic hydrocephalus, flow parameters were estimated from the two MRI sequences to assess CSF motion in the entire intracranial region.

METHODS

This study included 127 healthy volunteers aged ≥ 20 years and 44 patients with Hakim's disease. On 4D flow MRI for measuring CSF motion, velocity encoding was set at 5 cm/s. For the IVIM MRI analysis, the diffusion-weighted sequence was set at six b-values (i.e., 0, 50, 100, 250, 500, and 1000 s/mm2), and the biexponential IVIM fitting method was adapted. The relationships between the fraction of incoherent perfusion (f) on IVIM MRI and 4D flow MRI parameters including velocity amplitude (VA), absolute maximum velocity, stroke volume, net flow volume, and reverse flow rate were comprehensively evaluated in seven locations in the ventricles and subarachnoid spaces. Furthermore, we developed a new parameter for fluid oscillation, the Fluid Oscillation Index (FOI), by integrating these two measurements. In addition, we investigated the relationship between the measurements and indices specific to Hakim's disease and the FOIs in the entire intracranial space.

RESULTS

The VA on 4D flow MRI was significantly associated with the mean f-values on IVIM MRI. Therefore, we estimated VA that could not be directly measured on 4D flow MRI from the mean f-values on IVIM MRI in the intracranial CSF space, using the following formula; e0.2(f-85) + 0.25. To quantify fluid oscillation using one integrated parameter with weighting, FOI was calculated as VA × 10 + f × 0.02. In addition, the FOIs at the left foramen of Luschka had the strongest correlations with the Evans index (Pearson's correlation coefficient: 0.78). The other indices related with Hakim's disease were significantly associated with the FOIs at the cerebral aqueduct and bilateral foramina of Luschka. FOI at the cerebral aqueduct was also elevated in healthy controls aged ≥ 60 years.

CONCLUSIONS

We estimated pulsatile CSF movements in the entire intracranial CSF space in healthy individuals and patients with Hakim's disease using FOI integrating VA from 4D flow MRI and f-values from IVIM MRI. FOI is useful for quantifying the CSF oscillation.

Atypical Presentation of Longstanding Overt Ventriculomegaly in Adults: A Case Report

Hydrocephalus involves the enlargement of the ventricular system due to increased cerebrospinal fluid. This condition often presents with ventriculomegaly, associated with cognitive decline, gait disturbances, visual changes, and other neurological symptoms. In adults, hydrocephalus may result from longstanding overt ventriculomegaly in adults (LOVA), characterized by macrocephaly, subnormal IQ, urinary incontinence, and gait issues. In a recent case report, a 52-year-old Hispanic female displayed similar predisposing factors and radiological findings for a LOVA diagnosis. Despite the absence of focal neurological deficits or typical complaints, she experienced a breakthrough seizure episode after years without incident.

Impact of the Ventricle Size on Alzheimer's Disease Progression: A Retrospective Longitudinal Study

Background and Purpose

Ventricle enlargement has been implicated in the pathophysiology of Alzheimer's disease (AD). We studied the relationship between ventricular size and cognitive function in patients with AD. We focused on the effect of the initial ventricle size on the rate of cognitive decline in patients with AD.

Methods

A retrospective analysis of probable clinical AD participants with more than 2 magnetic resonance imaging images was performed. To measure ventricle size, we used visual rating scales of (1) Cardiovascular Health Study (CHS) score and (2) conventional linear measurement method.

Results

Increased clinical dementia rating (CDR) was correlated with a decreased Mini-Mental Status Examination (MMSE) score, and increased medial temporal lobe atrophy (MTLA) and global ventricle size (p<0.001, p<0.001, p=0.021, respectively). There was a significant correlation between the change in cognitive function in the group (70%-100%ile) with a large initial ventricle size (p=0.021 for ΔCDR, p=0.01 for ΔMMSE), while the median ventricle size (30%-70%ile) showed correlation with other brain structural changes (MTLA, frontal atrophy [FA], and white matter) (p=0.036 for initial MTLA, p=0.034 for FA).

Conclusions

In this study, the initial ventricle size may be a potential new imaging biomarker for initial cognitive function and clinical progression in AD. We found a relationship between the initial ventricle size and initial AD-related brain structural biomarkers.

Automatic assessment of disproportionately enlarged subarachnoid-space hydrocephalus from 3D MRI using two deep learning models

Background

Disproportionately enlarged subarachnoid-space hydrocephalus (DESH) is a key feature for Hakim disease (idiopathic normal pressure hydrocephalus: iNPH), but subjectively evaluated. To develop automatic quantitative assessment of DESH with automatic segmentation using combined deep learning models.

Methods

This study included 180 participants (42 Hakim patients, 138 healthy volunteers; 78 males, 102 females). Overall, 159 three-dimensional (3D) T1-weighted and 180 T2-weighted MRIs were included. As a semantic segmentation, 3D MRIs were automatically segmented in the total ventricles, total subarachnoid space (SAS), high-convexity SAS, and Sylvian fissure and basal cistern on the 3D U-Net model. As an image classification, DESH, ventricular dilatation (VD), tightened sulci in the high convexities (THC), and Sylvian fissure dilatation (SFD) were automatically assessed on the multimodal convolutional neural network (CNN) model. For both deep learning models, 110 T1- and 130 T2-weighted MRIs were used for training, 30 T1- and 30 T2-weighted MRIs for internal validation, and the remaining 19 T1- and 20 T2-weighted MRIs for external validation. Dice score was calculated as (overlapping area) × 2/total area.

Results

Automatic region extraction from 3D T1- and T2-weighted MRI was accurate for the total ventricles (mean Dice scores: 0.85 and 0.83), Sylvian fissure and basal cistern (0.70 and 0.69), and high-convexity SAS (0.68 and 0.60), respectively. Automatic determination of DESH, VD, THC, and SFD from the segmented regions on the multimodal CNN model was sufficiently reliable; all of the mean softmax probability scores were exceeded by 0.95. All of the areas under the receiver-operating characteristic curves of the DESH, Venthi, and Sylhi indexes calculated by the segmented regions for detecting DESH were exceeded by 0.97.

Conclusion

Using 3D U-Net and a multimodal CNN, DESH was automatically detected with automatically segmented regions from 3D MRIs. Our developed diagnostic support tool can improve the precision of Hakim disease (iNPH) diagnosis.

Magnetic Resonance Imaging Diagnosis in Normal Pressure Hydrocephalus

BACKGROUND

Idiopatic normal pressure hydrocephalus (iNPH) is a progressive neurologic syndrome featured by the triad of gait disturbance, mental deterioration and urinary incontinence, associated with ventriculomegaly and normal cerebrospinal fluid (CSF) pressure. The clinical presentation may be atypical or incomplete, or mimicked by other diseases, so conventional neuroradiologic imaging plays an important role in defining this pathology. iNPH pathophysiologic mechanisms have not yet been fully elucidated, although several studies have demonstrated the involvement of the glymphatic system, a highly organized fluid transport system, the malfunction of which is involved in the pathogenesis of several disorders including normotensive hydrocephalus.

METHODS

Recent studies have shown how crucial in the diagnosis of this pathology is the definition of morphologic biomarkers, such as ventricular enlargement disproportionate to cerebral atrophy and associated ballooning of frontal horns; periventricular hyperintensities; and corpus callosum thinning and elevation, with callosal angle <90 degrees.

RESULTS

Another interesting feature that is becoming a well-recognized factor to look for and useful for the diagnosis of iNPH is disproportionately enlarged subarachnoid space hydrocephalus, which includes enlarged ventricles, tight high-convexity and medial surface subarachnoid spaces, and expanded Sylvian fissures. A correct choice of MRI sequences is important for a proper characterization identification of others diseases that may underlie this pathology. Magnetic resonance imaging allows us to evaluate CSF flow, enabling us to define qualitative and quantitative parameters necessary for the purpose of accurate iNPH diagnosis.

CONCLUSIONS

iNPH can represent a real diagnostic challenge; a proper correlation among clinical features, traditional MRI, and CSF dynamics analysis can lead to a correct diagnosis.

Age-Related Changes in Cerebrospinal Fluid Dynamics in the Pathogenesis of Chronic Hydrocephalus in Adults

Cerebrospinal fluid (CSF) dynamics has dramatically changed in this century. In the latest concept of CSF dynamics, CSF is thought to be produced mainly from interstitial fluid excreted from the brain parenchyma and is absorbed in the meningeal lymphatics. Moreover, CSF does not always flow from the ventricles to the subarachnoid space unidirectionally through the foramina of Magendie and Luschka. In an environment of increased intracranial CSF in idiopathic normal pressure hydrocephalus, CSF freely moves through the inferior choroidal point of the choroidal fissure, which interfaces between the inferior horn of the lateral ventricles and the ambient cistern and through the velum interpositum between the third ventricle and the quadrigeminal cistern. The structure of the hippocampus adjacent to the inferior part of the choroidal fissure may be important in preventing the accumulation of waste products in the hippocampus. A recent imaging technology for CSF dynamics, such as four-dimensional flow and intravoxel incoherent motion magnetic resonance imaging, can visualize and quantify the pulsatile complex CSF motion in clinical usage. We present the current concepts of CSF dynamics with advanced magnetic resonance imaging techniques, which will be helpful in the management and understanding of the pathogenesis of chronic hydrocephalus in adults.

Aging-related volume changes in the brain and cerebrospinal fluid using artificial intelligence-automated segmentation

OBJECTIVES

To verify the reliability of the volumes automatically segmented using a new artificial intelligence (AI)-based application and evaluate changes in the brain and CSF volume with healthy aging.

METHODS

The intracranial spaces were automatically segmented in the 21 brain subregions and 5 CSF subregions using the AI-based application on the 3D T1-weighted images in healthy volunteers aged > 20 years. Additionally, the automatically segmented volumes of the total ventricles and subarachnoid spaces were compared with the manually segmented volumes of those extracted from 3D T2-weighted images using the intra-class correlation and Bland-Altman analysis.

RESULTS

In this study, 133 healthy volunteers aged 21-92 years were included. The mean intra-class correlations between the automatically and manually segmented volumes of the total ventricles and subarachnoid spaces were 0.986 and 0.882, respectively. The increase in the CSF volume was estimated to be approximately 30 mL (2%) per decade from 265 mL (18.7%) in the 20s to 488 mL (33.7%) in ages above 80 years; however, the increase in the volume of total ventricles was approximately 20 mL (< 2%) until the 60s and increased in ages above 60 years.

CONCLUSIONS

This study confirmed the reliability of the CSF volumes using the AI-based auto-segmentation application. The intracranial CSF volume increased linearly because of the brain volume reduction with aging; however, the ventricular volume did not change until the age of 60 years and above and then gradually increased. This finding could help elucidate the pathogenesis of chronic hydrocephalus in adults.

KEY POINTS

• The brain and CSF spaces were automatically segmented using an artificial intelligence-based application. • The total subarachnoid spaces increased linearly with aging, whereas the total ventricle volume was around 20 mL (< 2%) until the 60s and increased in ages above 60 years. • The cortical gray matter gradually decreases with aging, whereas the subcortical gray matter maintains its volume, and the cerebral white matter increases slightly until the 40s and begins to decrease from the 50s.

High homocysteine is associated with idiopathic normal pressure hydrocephalus in deep perforating arteriopathy: a cross-sectional study

BACKGROUND AND OBJECTIVE

The pathogenesis and pathophysiology of idiopathic normal pressure hydrocephalus (iNPH) remain unclear. Homocysteine may reduce the compliance of intracranial arteries and damage the endothelial function of the blood-brain barrier (BBB), which may be the underlying mechanism of iNPH. The overlap cases between deep perforating arteriopathy (DPA) and iNPH were not rare for the shared risk factors. We aimed to investigate the relationship between serum homocysteine and iNPH in DPA.

METHODS

A total of 41 DPA patients with iNPH and 49 DPA patients without iNPH were included. Demographic characteristics, vascular risk factors, laboratory results, and neuroimaging data were collected. Multivariable logistic regression analysis was performed to investigate the relationship between serum homocysteine and iNPH in DPA patients.

RESULTS

Patients with iNPH had significantly higher homocysteine levels than those without iNPH (median, 16.34 mmol/L versus 14.28 mmol/L; P = 0.002). There was no significant difference in CSVD burden scores between patients with iNPH and patients without iNPH. Univariate logistic regression analysis demonstrated that patients with homocysteine levels in the Tertile3 were more likely to have iNPH than those in the Tertile1 (OR, 4.929; 95% CI, 1.612-15.071; P = 0.005). The association remained significant after multivariable adjustment for potential confounders, including age, male, hypertension, diabetes mellitus, atherosclerotic cardiovascular disease (ASCVD) or hypercholesterolemia, and eGFR level.

CONCLUSION

Our study indicated that high serum homocysteine levels were independently associated with iNPH in DPA. However, further research is needed to determine the predictive value of homocysteine and to confirm the underlying mechanism between homocysteine and iNPH.

The Olfactory Bulb in Companion Animals-Anatomy, Physiology, and Clinical Importance

The Olfactory Bulb is a component of the Olfactory System, in which it plays an essential role as an interface between the peripheral components and the cerebral cortex responsible for olfactory interpretation and discrimination. It is in this element that the first selective integration of olfactory stimuli occurs through a complex cell interaction that forwards the received olfactory information to higher cortical centers. Considering its position in the organizational hierarchy of the olfactory system, it is now known that changes in the Olfactory Bulb can lead to olfactory abnormalities. Through imaging techniques, it was possible to establish relationships between the occurrence of changes secondary to brain aging and senility, neurodegenerative diseases, head trauma, and infectious diseases with a decrease in the size of the Olfactory Bulb and in olfactory acuity. In companion animals, this relationship has also been identified, with observations of relations between the cranial conformation, the disposition, size, and shape of the Olfactory Bulb, and the occurrence of structural alterations associated with diseases with different etiologies. However, greater difficulty in quantitatively assessing olfactory acuity in animals and a manifestly smaller number of studies dedicated to this topic maintain a lack of concrete and unequivocal results in this field of veterinary sciences. The aim of this work is to revisit the Olfactory Bulb in companion animals in all its dimensions, review its anatomy and histological characteristics, physiological integration in the olfactory system, importance as a potential early indicator of the establishment of specific pathologies, as well as techniques of imaging evaluation for its in vivo clinical exploration.

Usefulness of intravoxel incoherent motion MRI for visualizing slow cerebrospinal fluid motion

BACKGROUND

In the cerebrospinal fluid (CSF) dynamics, the pulsations of cerebral arteries and brain is considered the main driving force for the reciprocating bidirectional CSF movements. However, measuring these complex CSF movements on conventional flow-related MRI methods is difficult. We tried to visualize and quantify the CSF motion by using intravoxel incoherent motion (IVIM) MRI with low multi-b diffusion-weighted imaging.

METHODS

Diffusion-weighted sequence with six b values (0, 50, 100, 250, 500, and 1000 s/mm²) was performed on 132 healthy volunteers aged ≥ 20 years and 36 patients with idiopathic normal pressure hydrocephalus (iNPH). The healthy volunteers were divided into three age groups (< 40, 40 to < 60, and ≥ 60 years). In the IVIM analysis, the bi-exponential IVIM fitting method using the Levenberg-Marquardt algorithm was adapted. The average, maximum, and minimum values of ADC, D, D*, and fraction of incoherent perfusion (f) calculated by IVIM were quantitatively measured in 45 regions of interests in the whole ventricles and subarachnoid spaces.

RESULTS

Compared with healthy controls aged ≥ 60 years, the iNPH group had significantly lower mean f values in all the parts of the lateral and 3rd ventricles, whereas significantly higher mean f value in the bilateral foramina of Luschka. In the bilateral Sylvian fossa, which contain the middle cerebral bifurcation, the mean f values increased gradually with increasing age, whereas those were significantly lower in the iNPH group. In the 45 regions of interests, the f values in the bilateral foramina of Luschka were the most positively correlated with the ventricular size and indices specific to iNPH, whereas that in the anterior part of the 3rd ventricle was the most negatively correlated with the ventricular size and indices specific to iNPH. Other parameters of ADC, D, and D* were not significantly different between the two groups in any locations.

CONCLUSIONS

The f value on IVIM MRI is useful for evaluating small pulsatile complex motion of CSF throughout the intracranial CSF spaces. Patients with iNPH had significantly lower mean f values in the whole lateral ventricles and 3rd ventricles and significantly higher mean f value in the bilateral foramina of Luschka, compared with healthy controls aged ≥ 60 years.

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

BACKGROUND AND OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Choroid plexus epithelium and its role in neurological diseases

Choroid plexus epithelial cells can secrete cerebrospinal fluid into the ventricles, serving as the major structural basis of the selective barrier between the neurological system and blood in the brain. In fact, choroid plexus epithelial cells release the majority of cerebrospinal fluid, which is connected with particular ion channels in choroid plexus epithelial cells. Choroid plexus epithelial cells also produce and secrete a number of essential growth factors and peptides that help the injured cerebrovascular system heal. The pathophysiology of major neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, as well as minor brain damage diseases like hydrocephalus and stroke is still unknown. Few studies have previously connected choroid plexus epithelial cells to the etiology of these serious brain disorders. Therefore, in the hopes of discovering novel treatment options for linked conditions, this review extensively analyzes the association between choroid plexus epithelial cells and the etiology of neurological diseases such as Alzheimer's disease and hydrocephalus. Finally, we review CPE based immunotherapy, choroid plexus cauterization, choroid plexus transplantation, and gene therapy.

Metabolic regulation of the neural stem cell fate: Unraveling new connections, establishing new concepts

The neural stem cell niche is a key regulator participating in the maintenance, regeneration, and repair of the brain. Within the niche neural stem cells (NSC) generate new neurons throughout life, which is important for tissue homeostasis and brain function. NSCs are regulated by intrinsic and extrinsic factors with cellular metabolism being lately recognized as one of the most important ones, with evidence suggesting that it may serve as a common signal integrator to ensure mammalian brain homeostasis. The aim of this review is to summarize recent insights into how metabolism affects NSC fate decisions in adult neural stem cell niches, with occasional referencing of embryonic neural stem cells when it is deemed necessary. Specifically, we will highlight the implication of mitochondria as crucial regulators of NSC fate decisions and the relationship between metabolism and ependymal cells. The link between primary cilia dysfunction in the region of hypothalamus and metabolic diseases will be examined as well. Lastly, the involvement of metabolic pathways in ependymal cell ciliogenesis and physiology regulation will be discussed.

Ependymal Cilia: Physiology and Role in Hydrocephalus

Cerebrospinal fluid (CSF), a colorless liquid that generally circulates from the lateral ventricles to the third and fourth ventricles, provides essential nutrients for brain homeostasis and growth factors during development. As evidenced by an increasing corpus of research, CSF serves a range of important functions. While it is considered that decreased CSF flow is associated to the development of hydrocephalus, it has recently been postulated that motile cilia, which line the apical surfaces of ependymal cells (ECs), play a role in stimulating CSF circulation by cilia beating. Ependymal cilia protrude from ECs, and their synchronous pulsing transports CSF from the lateral ventricle to the third and fourth ventricles, and then to the subarachnoid cavity for absorption. As a result, we postulated that malfunctioning ependymal cilia could disrupt normal CSF flow, raising the risk of hydrocephalus. This review aims to demonstrate the physiological functions of ependymal cilia, as well as how cilia immobility or disorientation causes problems. We also conclude conceivable ways of treatment of hydrocephalus currently for clinical application and provide theoretical support for regimen improvements by investigating the relationship between ependymal cilia and hydrocephalus development.

Targeting choroid plexus epithelium as a novel therapeutic strategy for hydrocephalus

The choroid plexus is a tissue located in the lateral ventricles of the brain and is composed mainly of choroid plexus epithelium cells. The main function is currently thought to be the secretion of cerebrospinal fluid and the regulation of its pH, and more functions are gradually being demonstrated. Assistance in the removal of metabolic waste and participation in the apoptotic pathway are also the functions of choroid plexus. Besides, it helps to repair the brain by regulating the secretion of neuropeptides and the delivery of drugs. It is involved in the immune response to assist in the clearance of infections in the central nervous system. It is now believed that the choroid plexus is in an inflammatory state after damage to the brain. This state, along with changes in the cilia, is thought to be an abnormal physiological state of the choroid plexus, which in turn leads to abnormal conditions in cerebrospinal fluid and triggers hydrocephalus. This review describes the pathophysiological mechanism of hydrocephalus following choroid plexus epithelium cell abnormalities based on the normal physiological functions of choroid plexus epithelium cells, and analyzes the attempts and future developments of using choroid plexus epithelium cells as a therapeutic target for hydrocephalus.

Advances in brain barriers and brain fluids research in 2021: great progress in a time of adversity

This editorial highlights advances in brain barrier and brain fluid research in 2021. It covers research on components of the blood–brain barrier, neurovascular unit and brain fluid systems; how brain barriers and brain fluid systems are impacted by neurological disorders and their role in disease progression; and advances in strategies for treating such disorders.

Sustained glymphatic transport and impaired drainage to the nasal cavity observed in multiciliated cell ciliopathies with hydrocephalus

Background

Hydrocephalus (increased ventricular size due to CSF accumulation) is a common finding in human ciliopathies and in mouse models with genetic depletion of the multiciliated cell (MCC) cilia machinery. However, the contribution of MCC to CSF dynamics and, the mechanism by which impaired MCC function leads to hydrocephalus remains poorly understood. The aim of our study was to examine if defects in MCC ciliogenesis and cilia-generated CSF flow impact central nervous system (CNS) fluid homeostasis including glymphatic transport and solute waste drainage.

Methods

We used two distinct mouse models of MCC ciliopathy: MCC-specific CEP164 conditional knockout mice (FOXJ1-Cre;CEP164^fl/fl (N = 10), 3-month-old) and p73 knock-out (p73^−/− (N = 8), 5-month-old) mice. Age-matched, wild-type littermates for each of the mutants served as controls. Glymphatic transport and solute drainage was quantified using in vivo T1 mapping by magnetic resonance imaging (MRI) after CSF infusion of gadoteric acid. Brain morphometry and aquaporin 4 expression (AQP4) was also assessed. Intracranial pressure (ICP) was measured in separate cohorts.

Results

In both of the two models of MCC ciliopathy we found the ventriculomegaly to be associated with normal ICP. We showed that FOXJ1-Cre;CEP164^fl/fl mice with hydrocephalus still demonstrated sustained glymphatic transport and normal AQP4 expression along capillaries. In p73^−/− mice glymphatic transport was even increased, and this was paralleled by an increase in AQP4 polarization around capillaries. Further, solute drainage via the cribriform plate to the nasal cavity was severely impaired in both ciliopathy models and associated with chronic rhinitis and olfactory bulb hypoplasia.

Conclusions

The combination of sustained glymphatic transport, impaired solute drainage via the cribriform plate to the nasal cavity and hydrocephalus has not previously been reported in models of MCC ciliopathy. Our data enhance our understanding of how different types of ciliopathies contribute to disruption of CNS fluid homeostasis, manifested in pathologies such as hydrocephalus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-022-00319-x.

Can Shunt Response in Patients with Idiopathic Normal Pressure Hydrocephalus Be Predicted from Preoperative Brain Imaging? A Retrospective Study of the Diagnostic Use of the Normal Pressure Hydrocephalus Radscale in 119 Patients

BACKGROUND AND PURPOSE

The Normal Pressure Hydrocephalus Radscale is a combined scoring of 7 different structural imaging markers on preoperative brain CT or MR imaging in patients with idiopathic normal pressure hydrocephalus: callosal angle, Evans Index, Sylvian fissure dilation, apical sulcal narrowing, mean temporal horn diameter, periventricular WM lesions, and focal sulcal dilation. The purpose of this retrospective study was to assess the performance of the Normal Pressure Hydrocephalus Radscale in distinguishing idiopathic normal pressure hydrocephalus shunt responders from nonresponders.

MATERIALS AND METHODS

The preoperative MR imaging and CT scans of 119 patients with idiopathic normal pressure hydrocephalus were scored using the Normal Pressure Hydrocephalus Radscale. A summary shunt-response score assessed within 6 months from ventriculoperitoneal shunt surgery, combining the effect on cognition, gait, and urinary incontinence, was used as a reference. The difference between the mean Normal Pressure Hydrocephalus Radscale for responders and nonresponders was tested using the Student t test. The area under the curve was calculated for the Normal Pressure Hydrocephalus Radscale to assess shunt response. To ascertain reproducibility, we assessed the interobserver agreement between the 2 independent observers as intraclass correlation coefficients for the Normal Pressure Hydrocephalus Radscale for 74 MR imaging scans and 19 CT scans.

RESULTS

Ninety-four (79%) of 119 patients were shunt responders. The mean Normal Pressure Hydrocephalus Radscale score for shunt responders was 8.35 (SD, 1.53), and for nonresponders, 7.48 (SD, 1.53) (P = .02). The area under the curve for the Normal Pressure Hydrocephalus Radscale was 0.66 (range, 0.54-0.78). The intraclass correlation coefficient for the Normal Pressure Hydrocephalus Radscale was 0.86 for MR imaging and 0.82 for CT.

CONCLUSIONS

The Normal Pressure Hydrocephalus Radscale showed moderate discrimination for shunt response but cannot, on its own, be used for selecting patients with idiopathic normal pressure hydrocephalus for shunt surgery.

Reconsidering Ventriculoperitoneal Shunt Surgery and Postoperative Shunt Valve Pressure Adjustment: Our Approaches Learned From Past Challenges and Failures

Treatment for idiopathic normal pressure hydrocephalus (iNPH) continues to develop. Although ventriculoperitoneal shunt surgery has a long history and is one of the most established neurosurgeries, in the 1970s, the improvement rate of iNPH triad symptoms was poor and the risks related to shunt implantation were high. This led experts to question the surgical indication for iNPH and, over the next 20 years, cerebrospinal fluid (CSF) shunt surgery for iNPH fell out of favor and was rarely performed. However, the development of programmable-pressure shunt valve devices has reduced the major complications associated with the CSF drainage volume and appears to have increased shunt effectiveness. In addition, the development of support devices for the placement of ventricular catheters including preoperative virtual simulation and navigation systems has increased the certainty of ventriculoperitoneal shunt surgery. Secure shunt implantation is the most important prognostic indicator, but ensuring optimal initial valve pressure is also important. Since over-drainage is most likely to occur in the month after shunting, it is generally believed that a high initial setting of shunt valve pressure is the safest option. However, this does not always result in sufficient improvement of the symptoms in the early period after shunting. In fact, evidence suggests that setting the optimal valve pressure early after shunting may cause symptoms to improve earlier. This leads to improved quality of life and better long-term independent living expectations. However, in iNPH patients, the remaining symptoms may worsen again after several years, even when there is initial improvement due to setting the optimal valve pressure early after shunting. Because of the possibility of insufficient CSF drainage, the valve pressure should be reduced by one step (2–4 cmH₂O) after 6 months to a year after shunting to maximize symptom improvement. After the valve pressure is reduced, a head CT scan is advised a month later.

Molecular Mechanisms and Risk Factors for the Pathogenesis of Hydrocephalus

Hydrocephalus is a neurological condition due to the aberrant circulation and/or obstruction of cerebrospinal fluid (CSF) flow with consequent enlargement of cerebral ventricular cavities. However, it is noticed that a lot of patients may still go through symptomatic progression despite standard shunting procedures, suggesting that hydrocephalus is far more complicated than a simple CSF circulative/obstructive disorder. Growing evidence indicates that genetic factors play a fundamental role in the pathogenesis of some hydrocephalus. Although the genetic research of hydrocephalus in humans is limited, many genetic loci of hydrocephalus have been defined in animal models. In general, the molecular abnormalities involved in the pathogenesis of hydrocephalus include brain development and ependymal cell dysfunction, apoptosis, inflammation, free radical generation, blood flow, and cerebral metabolism. Moreover, recent studies have indicated that the molecular abnormalities relevant to aberrant cerebral glymphatic drainage turn into an attractive subject in the CSF circulation disorder. Furthermore, the prevalent risk factors could facilitate the development of hydrocephalus. In this review, we elicited some possible fundamental molecular mechanisms and facilitating risk factors involved in the pathogenesis of hydrocephalus, and aimed to widen the diagnosis and therapeutic strategies for hydrocephalus management. Such knowledge could be used to improve patient care in different ways, such as early precise diagnosis and effective therapeutic regimens.

Neuropathological findings in possible normal pressure hydro-cephalus: A post-mortem study of 29 cases with lifelines

Aims: There are very few detailed post-mortem studies on idiopathic normal-pressure hydrocephalus (iNPH) and there is a lack of proper neuropathological criteria for iNPH. This study aims to update the knowledge on the neuropathology of iNPH and to develop the neuropathological diagnostic criteria of iNPH. Methods: We evaluated the clinical lifelines and post-mortem findings of 29 patients with possible NPH. Pre-mortem cortical brain biopsies were taken from all patients during an intracranial pressure measurement or a cerebrospinal fluid (CSF) shunt surgery. Results: The mean age at the time of the biopsy was 70±8 SD years and 74±7 SD years at the time of death. At the time of death, 11/29 patients (38%) displayed normal cognition or mild cognitive impairment (MCI), 9/29 (31%) moderate dementia and 9/29 (31%) severe dementia. Two of the demented patients had only scarce neuropathological findings indicating a probable hydrocephalic origin for the dementia. Amyloid-β (Aβ) and hyperphosphorylated τ (HPτ) in the biopsies predicted the neurodegenerative diseases so that there were 4 Aβ positive/low Alzheimer's disease neuropathological change (ADNC) cases, 4 Aβ positive/intermediate ADNC cases, 1 Aβ positive case with both low ADNC and progressive supranuclear palsy (PSP), 1 HPτ/PSP and primary age-related tauopathy (PART) case, 1 Aβ/HPτ and low ADNC/synucleinopathy case and 1 case with Aβ/HPτ and high ADNC. The most common cause of death was due to cardiovascular diseases (10/29, 34%), followed by cerebrovascular diseases or subdural hematoma (SDH) (8/29, 28%). Three patients died of a postoperative intracerebral hematoma (ICH). Vascular lesions were common (19/29, 65%). Conclusions: We update the suggested neuropathological diagnostic criteria of iNPH, which emphasize the rigorous exclusion of all other known possible neuropathological causes of dementia. Despite the first 2 probable cases reported here, the issue of "hydrocephalic dementia" as an independent entity still requires further confirmation. Extensive sampling (with fresh frozen tissue including meninges) with age-matched neurologically healthy controls is highly encouraged.

Clinical comorbidities correlated with a response to the cerebrospinal fluid tap test in idiopathic normal-pressure hydrocephalus

AIMS

The mainstay of treatment for idiopathic normal-pressure hydrocephalus (iNPH) is spinal fluid shunting. A tap test (TT) is recommended as an indication of shunting. Patients with iNPH are often elderly and have multiple comorbidities affecting the shunting outcome. We investigated the factors affecting TT in patients with iNPH.

METHODS

Seventy-five patients with iNPH were admitted to our department for a TT from April 2010 to May 2021. The patients were divided into a responsive group and an unresponsive group according to the clinical outcomes after TT on the Timed Up and Go Test (TUG), Mini-Mental State Examination (MMSE), or iNPH grading scale. Factors affecting the TT were compared between the responders and nonresponders.

RESULTS

There were 38 patients (50.7%) in the TT responder group, and the prevalence of improvement was 82.9% in the TUG, 27.6% in the MMSE, and 76.3% in the iNPH grading scale. There were no significant differences in the vascular risk factors between the two groups. The prevalence of lumbar spondylosis, compression fracture, severe periventricular hyperintensity, deep and subcortical white matter hyperintensity (DSWMH), and old cerebral infarcts was significantly higher among the TT nonresponders. The logistic regression analysis showed that severe DSWMH and lumbar spondylosis were associated with a TT nonresponse (p < 0.001 and p = 0.003, respectively). Shunting was performed in 22 patients, 19 of whom were TT responders.

CONCLUSION

Severe DSWMH and lumbar spondylosis were associated with a poor response to the TT in iNPH patients. We should consider risk factors when selecting candidates for shunt surgery.