History, Anatomy, Histology, and Embryology of the Ventricles and Physiology of the Cerebrospinal Fluid

Cerebrospinal fluid is an essential, clear, and colorless liquid for the homeostasis of the brain and neuronal functioning. It circulates in the brain ventricles, the cranial and spinal subarachnoid spaces. The mean cerebrospinal fluid volume is 150 ml, with 125 ml in subarachnoid spaces and 25 ml in the ventricles. Cerebrospinal fluid is mainly secreted by the choroid plexuses. Cerebrospinal fluid secretion in adults ranges between 400 and 600 ml per day and it is renewed about four or five times a day. Cerebrospinal fluid is mainly reabsorbed from arachnoid granulations. Any disruption in this well-regulated system from overproduction to decreased absorption or obstruction could lead to hydrocephalus.

Choroid plexus enlargement is associated with neuroinflammation and reduction of blood brain barrier permeability in depression

Background: Recent studies have shown that choroid plexuses (CP) may be involved in the neuro-immune axes, playing a role in the interaction between the central and peripheral inflammation. Here we aimed to investigate CP volume alterations in depression and their associations with inflammation. Methods: 51 depressed participants (HDRS score >13) and 25 age- and sex-matched healthy controls (HCs) from the Wellcome Trust NIMA consortium were re-analysed for the study. All the participants underwent full peripheral cytokine profiling and simultaneous [11C]PK11195 PET/structural MRI imaging for measuring neuroinflammation and CP volume respectively. Results: We found a significantly greater CP volume in depressed subjects compared to HCs (t(76) = +2.17) that was positively correlated with [11C]PK11195 PET binding in the anterior cingulate cortex (r=0.28, p=0.02), prefrontal cortex (r=0.24, p=0.04), and insular cortex (r=0.24, p=0.04), but not with the peripheral inflammatory markers: CRP levels (r=0.07, p=0.53), IL-6 (r=-0.08, p=0.61), and TNF-α (r=-0.06, p=0.70). The CP volume correlated with the [11C]PK11195 PET binding in CP (r=0.34, p=0.005). Integration of transcriptomic data from the Allen Human Brain Atlas with the brain map depicting the correlations between CP volume and PET imaging found significant gene enrichment for several pathways involved in neuroinflammatory response. Conclusion: This result supports the hypothesis that changes in brain barriers may cause reduction in solute exchanges between blood and CSF, disturbing the brain homeostasis and ultimately contributing to inflammation in depression. Given that CP anomalies have been recently detected in other brain disorders, these results may not be specific to depression and might extend to other conditions with a peripheral inflammatory component.

Mechanisms of brain protection against autoimmune inflammation

A significant number of unique antigens expressed in the brain can activate an adaptive immune response, increasing the risk of autoimmune inflammation in the central nervous system (CNS). As a result, a complex protection system exists in the CNS to prevent autoimmune reactions. In addition to the blood-brain- and blood-cerebrospinal fluid-barriers, we discuss complex systems of antigen drainage and circulation of antigen-presenting cells in the CNS. Moreover, the interaction of the CNS with the peripheral immune system typically occurs in specific areas (choroid plexuses, perivascular spaces, and brain meninges), and resident cells of the innate immune system (macrophages, microglia, astrocytes) have limited opportunities for antigen presentation and do not migrate to regional lymph nodes. There are signs of activation of adaptive immunity against CNS antigens in normal conditions, which, however, do not lead to autoimmune diseases. The review covers the mechanisms of maintaining natural immune self-tolerance in the CNS and their failure in autoimmune CNS pathology.

Axial multi-layer perceptron architecture for automatic segmentation of choroid plexus in multiple sclerosis

Choroid plexuses (CP) are structures of the ventricles of the brain which produce most of the cerebrospinal fluid (CSF). Several postmortem and in vivo studies have pointed towards their role in the inflammatory process in multiple sclerosis (MS). Automatic segmentation of CP from MRI thus has high value for studying their characteristics in large cohorts of patients. To the best of our knowledge, the only freely available tool for CP segmentation is FreeSurfer but its accuracy for this specific structure is poor. In this paper, we propose to automatically segment CP from non-contrast enhanced T1-weighted MRI. To that end, we introduce a new model called "Axial-MLP" based on an assembly of Axial multi-layer perceptrons (MLPs). This is inspired by recent works which showed that the self-attention layers of Transformers can be replaced with MLPs. This approach is systematically compared with a standard 3D U-Net, nnU-Net, Freesurfer and FastSurfer. For our experiments, we make use of a dataset of 141 subjects (44 controls and 97 patients with MS). We show that all the tested deep learning (DL) methods outperform FreeSurfer (Dice around 0.7 for DL vs 0.33 for FreeSurfer). Axial-MLP is competitive with U-Nets even though it is slightly less accurate. The conclusions of our paper are two-fold: 1) the studied deep learning methods could be useful tools to study CP in large cohorts of MS patients; 2)~Axial-MLP is a potentially viable alternative to convolutional neural networks for such tasks, although it could benefit from further improvements.

Isolated intracranial hypertension associated with COVID-19

Background Headache is a frequent complaint in COVID-19 patients. However, no detailed information on headache characteristics is provided in these reports. Our objective is to describe the characteristics of headache and the cerebrospinal fluid (CSF) profile in COVID-19 patients, highlighting the cases of isolated intracranial hypertension. Methods In this cross-sectional study, we selected COVID-19 patients who underwent lumbar puncture due to neurological complaints from April to May 2020. We reviewed clinical, imaging, and laboratory data of patients with refractory headache in the absence of other encephalitic or meningitic features. CSF opening pressures higher than 250 mmH2O were considered elevated, and from 200 to 250 mmH2O equivocal. Results Fifty-six COVID-19 patients underwent lumbar puncture for different neurological conditions. A new, persistent headache that prompted a CSF analysis was diagnosed in 13 (23.2%). The pain was throbbing, holocranial or bilateral in the majority of patients. All patients had normal CSF analysis and RT-qPCR for SARS-CoV-2 was negative in all samples. Opening pressure >200 mmH2O was present in 11 patients and, in six of these, > 250 mmH2O. 6/13 patients had complete improvement of the pain, five had partial improvement, and two were left with a daily persistent headache. Conclusions In a significant proportion of COVID-19 patients, headache was associated to intracranial hypertension in the absence of meningitic or encephalitic features. Coagulopathy associated with COVID-19 could be an explanation, but further studies including post-mortem analysis of areas of production and CSF absorption (choroid plexuses and arachnoid granulations) are necessary to clarify this issue.

Late diagnosis of isolated central diabetes insipidus secondary to congenital toxoplasmosis—case report

ABSTRACT Congenital toxoplasmosis is an uncommon infection. Hypothalamic/pituitary involvement leading to isolated central diabetes insipidus is extremely rare. Making a correct diagnosis of this condition, albeit challenging, is crucial for adequate management. We present a 54-year-old female who developed central diabetes insipidus as a complication of congenital toxoplasmosis. She had polydipsia and hypernatraemia on presentation and responded to intranasal desmopressin with normalization of above-mentioned findings. Magnetic resonance imaging and cranial X-ray’s showed pronounced intracranial calcifications in both choroid plexuses. Thyroid function tests, serum cortisol level and anterior pituitary function were all normal. To the best of our knowledge, this is the first reported case of isolated diabetes insipidus due to congenital toxoplasmosis in literature diagnosed late in adulthood and gives an insight into the challenges of diagnosing central diabetes insipidus and the hypothalamic/pituitary involvement in cases of congenital toxoplasmosis.

Targeting the Choroid Plexuses for Protein Drug Delivery

Delivery of therapeutic agents to the central nervous system is challenged by the barriers in place to regulate brain homeostasis. This is especially true for protein therapeutics. Targeting the barrier formed by the choroid plexuses at the interfaces of the systemic circulation and ventricular system may be a surrogate brain delivery strategy to circumvent the blood-brain barrier. Heterogenous cell populations located at the choroid plexuses provide diverse functions in regulating the exchange of material within the ventricular space. Receptor-mediated transcytosis may be a promising mechanism to deliver protein therapeutics across the tight junctions formed by choroid plexus epithelial cells. However, cerebrospinal fluid flow and other barriers formed by ependymal cells and perivascular spaces should also be considered for evaluation of protein therapeutic disposition. Various preclinical methods have been applied to delineate protein transport across the choroid plexuses, including imaging strategies, ventriculocisternal perfusions, and primary choroid plexus epithelial cell models. When used in combination with simultaneous measures of cerebrospinal fluid dynamics, they can yield important insight into pharmacokinetic properties within the brain. This review aims to provide an overview of the choroid plexuses and ventricular system to address their function as a barrier to pharmaceutical interventions and relevance for central nervous system drug delivery of protein therapeutics. Protein therapeutics targeting the ventricular system may provide new approaches in treating central nervous system diseases.

Monocyte recruitment to the inflamed central nervous system: migration pathways and distinct functional polarization

ABSTRACTThe central nervous system (CNS) parenchyma is enclosed by anatomical interfaces including multilayered meninges, the blood-brain barrier (BBB), the choroid plexuses within ventricles and the glia limitans. These border areas hold distinct functional specializations which control the trafficking of monocyte-derived cells toward the CNS parenchyma, altogether maintaining CNS homeostasis. By crossing activated endothelial, epithelial and glial borders, circulating leukocytes gain however access to the CNS parenchyma in several inflammatory diseases including multiple sclerosis.Studies in animal models of neuroinflammation have helped describing the phenotypic specifications of these invading monocyte-derived cells, able to exert detrimental or beneficial functions depending on the local environment. In this context, in vivo visualization of iNOS+ pro-inflammatory and arginase-1+ anti-inflammatory macrophages has recently revealed that these distinct cell phenotypes are highly compartmentalized by CNS borders. While arginase-1+ macrophages densely populate the leptomeninges, iNOS+ macrophages rather accumulate in perivascular spaces and at the pia mater-CNS parenchymal interface.How and where these macrophages acquire their functional commitment, and whether differentially-activated monocyte-derived cells infiltrate the CNS through distinct gateways, remains however unclear.In this study, we have investigated the interaction of monocyte-derived macrophages with endothelial (BBB) and epithelial (choroid plexus) barriers of the CNS, both in vitro and in vivo. By using primary mouse brain microvascular endothelial cells as in vitro model of the BBB, we observed that, compared to unpolarized primary macrophages, adhesion of functionally-committed macrophages to endothelial cells was drastically reduced, literally abrogating their diapedesis across the BBB. Conversely, when interacting with an activated choroid plexus epithelium, both pro- and anti-inflammatory macrophages displayed substantial adhesive and migratory properties. Accordingly, in vivo analysis of choroid plexuses revealed increased macrophage trafficking and a scattered presence of polarized cells upon induction of anti-CNS inflammation.Altogether, we show that acquisition of distinct macrophage polarizations significantly alters the adhesive and migratory properties of these cells in a barrier-specific fashion. While monocytes trafficking at the level of the BBB seem to acquire their signature phenotype only following diapedesis, other anatomical interfaces can be the entry site for functionally activated monocyte-derived cells. Our study highlights the choroid plexus as a key access gateway for macrophages during neuroinflammation, and its stroma as a potential priming site for their functional polarization.

Pineal gland calcifications in patients with benign and malignant tumors of the larynx, pharynx, paranasal sinuses and auditory nerve

Calcifications of the brain – pineal gland, choroid plexuses of the lateral ventricles – are a long-known phenomenon. Calcification in such functionally important organs as the pineal gland and choroid plexuses of the lateral ventricles cannot be physiological (it is enough to recall the formation of stones in the gallbladder, kidneys, prostate gland, calcinosis of the heart valves and coronary vessels) or relatively neutral process in the body and not affect the activity of these organs. The purpose of the investigation is to study the nosological predisposition of calcifications and the incidence of calcification of the pineal gland and choroid plexuses of the lateral ventricles in benign and malignant tumors of the larynx, pharynx, paranasal sinuses and auditory nerve. Material and research methods. The analysis of CT images of 425 persons was carried out (data archive of the Institute): 50 practically healthy persons from 22 to 60 years without any chronic diseases of the head and neck and a history of surgical interventions; 23 – from 61 to 74 years with normal body aging, not taking any medications, with healthy lifestyle; 235 – from 22 to 74 years with maxillary sinus cysts; 61 – from 28 to 71 years with acoustic neuromas; 56 – from 14 to 74 years with benign and malignant tumors of the larynx, nasal pharynx and paranasal sinuses. Conclusions. Pineal gland calcifications – can be considered as: mobile depot or cemetery of calcium; the result of an organ and/or a tumor-bearing organism protective reaction; a sign of a normal or decreased pineal gland function. The formation and growth of calcifications of the pineal gland and choroid plexuses of the lateral ventricles is associated with the growth and development of the body, benign and malignant tumors of the larynx, pharynx, paranasal sinuses and the auditory nerve (very likely, the tumors of other localizations as well). The formation and growth of calcifications of the pineal gland and choroid plexuses of the lateral ventricles indicates an increase of the heterogeneity of the human body tissues and organs with age and the acquisition of diseases.