Involvement of the glymphatic/meningeal lymphatic system in Alzheimer's disease: insights into proteostasis and future directions

BACKGROUND

 Alzheimer's disease (AD) is pathologically characterized by the abnormal accumulation of Aβ and tau proteins. There has long been a keen interest among researchers in understanding how Aβ and tau are ultimately cleared in the brain. The discovery of this glymphatic system introduced a novel perspective on protein clearance and it gained recognition as one of the major brain clearance pathways for clearing these pathogenic proteins in AD. This finding has sparked interest in exploring the potential contribution of the glymphatic/meningeal lymphatic system in AD. Furthermore, there is a growing emphasis and discussion regarding the possibility that activating the glymphatic/meningeal lymphatic system could serve as a novel therapeutic strategy against AD.

OBJECTIVES

 Given this current research trend, the primary focus of this comprehensive review is to highlight the role of the glymphatic/meningeal lymphatic system in the pathogenesis of AD. The discussion will encompass future research directions and prospects for treatment in relation to the glymphatic/meningeal lymphatic system.

Highly Sensitive 3-Tesla Real Inversion Recovery MRI Detects Leptomeningeal Contrast Enhancement in Chronic Active Multiple Sclerosis

BACKGROUND

Leptomeningeal contrast enhancement (LME) on T2-weighted Fluid-Attenuated Inversion Recovery (T2-FLAIR) MRI is a reported marker of leptomeningeal inflammation, which is known to be associated with progression of multiple sclerosis (MS). However, this MRI approach, as typically implemented on clinical 3-tesla (T) systems, detects only a few enhancing foci in ~25% of patients and has thus been criticized as poorly sensitive.

PURPOSE

To compare an optimized 3D real-reconstruction inversion recovery (Real-IR) MRI sequence on a clinical 3 T scanner to T2-FLAIR for prevalence, characteristics, and clinical/radiological correlations of LME.

MATERIALS AND METHODS

We obtained 3D T2-FLAIR and Real-IR scans before and after administration of standard-dose gadobutrol in 177 scans of 154 participants (98 women, 64%; mean ± SD age: 49 ± 12 years), including 124 with an MS-spectrum diagnosis, 21 with other neurological and/or inflammatory disorders, and 9 without neurological history. We calculated contrast-to-noise ratios (CNR) in 20 representative LME foci and determined association of LME with cortical lesions identified at 7 T (n = 19), paramagnetic rim lesions (PRL) at 3 T (n = 105), and clinical/demographic data.

RESULTS

We observed focal LME in 73% of participants on Real-IR (70% in established MS, 33% in healthy volunteers, P < 0.0001), compared to 33% on T2-FLAIR (34% vs. 11%, P = 0.0002). Real-IR showed 3.7-fold more LME foci than T2-FLAIR ( P = 0.001), including all T2-FLAIR foci. LME CNR was 2.5-fold higher by Real-IR ( P < 0.0001). The major determinant of LME status was age. Although LME was not associated with cortical lesions, the number of PRL was associated with the number of LME foci on both T2-FLAIR ( P = 0.003) and Real-IR ( P = 0.0003) after adjusting for age, sex, and white matter lesion volume.

CONCLUSIONS

Real-IR a promising tool to detect, characterize, and understand the significance of LME in MS. The association between PRL and LME highlights a possible role of the leptomeninges in sustaining chronic inflammation.

Discrimination of leptomeningeal carcinomatosis and meningeal inflammation/infection with internal acoustic canal enhancement

PURPOSE

The purpose of this study is to investigate whether the presence and pattern of enhancement at the internal acoustic canal (IAC) could help in discriminating between leptomeningeal carcinomatosis (LCa) and meningeal inflammation/infection (MMI).

METHODS

Magnetic resonance (MR) images of patients with leptomeningeal enhancement were retrospectively evaluated. MR images of the LCa group (n = 33), MMI group (n = 19) and control group (n = 33) were evaluated for the presence, type (moderate/prominent), and localization (unilateral/bilateral) of the IAC enhancement.

RESULTS

The presence of IAC enhancement was significantly more common in patients with LCa (p < 0.001). In 73.7 % of patients with MMI, no contrast enhancement was observed in the IAC. In patients with contrast enhancement in the IAC, the risk of LCa in the etiology is 20 times greater than the risk of having MMI. Seventy-five percent of the IAC enhancement seen in LCa patients and 20 % of the IAC enhancements seen in MMI patients was bilateral. This difference was statistically significant (p = 0.029).

CONCLUSION

Intense contrast enhancement of the IAC can be a marker for LCa.

Leptomeningeal Carcinomatosis from Solid Tumor Malignancies: Treatment Strategies and Biomarkers

Leptomeningeal metastases/diseases (LMDs) are a late-stage complication of solid tumor or hematologic malignancies. LMD is spread of cancer cells to the layers of the leptomeninges (pia and arachnoid maters) and subarachnoid space seen in 3 to 5% of cancer patients. It is a disseminated disease which carries with it significant neurologic morbidity and mortality. Our understanding of disease pathophysiology is currently lacking; however, advances are being made. As our knowledge of disease pathogenesis has improved, treatment strategies have evolved. Mainstays of treatment such as radiotherapy have changed from involved-field radiotherapy strategies to proton craniospinal irradiation which has demonstrated promising results in recent clinical trials. Systemic treatment strategies have also improved from more traditional chemotherapeutics with limited central nervous system (CNS) penetration to more targeted therapies with better CNS tumor response. Many challenges remain from earlier clinical detection of disease through improvement of active treatment options, but we are getting closer to meaningful treatment.

Meningoencephalomyelitis associated with foreign plant material in a dog: case report and brief literature review

Neurologic disease associated with migration of plant material is reported infrequently in dogs. Here we describe meningoencephalomyelitis associated with foreign plant material in a 2-y-old castrated male West Highland White Terrier dog with acute neck pain. Magnetic resonance imaging revealed spinal meningeal contrast enhancement. Although clinical signs improved after treatment with steroids, the dog was readmitted for further evaluation 3-mo later and was euthanized after generalized epileptic seizures. Autopsy findings consisted of coalescing, pus-filled, neuroparenchymal cavitations surrounded by hemorrhage in the left caudal colliculus and rostral left cerebellar hemisphere. Histologically, lesions consisted of necrosis and suppuration, which surrounded a 1 × 2-mm foreign body morphologically consistent with plant material and clusters of gram-positive bacterial cocci. Affected areas were surrounded by reactive astrocytes, fibrous connective tissue, and mixed inflammatory infiltrates. Areas of hemorrhage and infiltration by neutrophils and foamy macrophages with fibrinoid change of small capillaries were observed in the adjacent neuroparenchyma. The inflammation extended to the perivascular spaces in the leptomeninges (mesencephalon, cerebellum, and brainstem, and spinal cord) and spinal central canal. Anaerobic bacterial culture of frozen samples of cerebellum yielded heavy growth of Bacteroides pyogenes.

Current views on meningeal lymphatics and immunity in aging and Alzheimer's disease

Alzheimer's disease (AD) is an aging-related form of dementia associated with the accumulation of pathological aggregates of amyloid beta and neurofibrillary tangles in the brain. These phenomena are accompanied by exacerbated inflammation and marked neuronal loss, which altogether contribute to accelerated cognitive decline. The multifactorial nature of AD, allied to our still limited knowledge of its etiology and pathophysiology, have lessened our capacity to develop effective treatments for AD patients. Over the last few decades, genome wide association studies and biomarker development, alongside mechanistic experiments involving animal models, have identified different immune components that play key roles in the modulation of brain pathology in AD, affecting its progression and severity. As we will relay in this review, much of the recent efforts have been directed to better understanding the role of brain innate immunity, and particularly of microglia. However, and despite the lack of diversity within brain resident immune cells, the brain border tissues, especially the meninges, harbour a considerable number of different types and subtypes of adaptive and innate immune cells. Alongside microglia, which have taken the centre stage as important players in AD research, there is new and exciting evidence pointing to adaptive immune cells, namely T and B cells found in the brain and its meninges, as important modulators of neuroinflammation and neuronal (dys)function in AD. Importantly, a genuine and functional lymphatic vascular network is present around the brain in the outermost meningeal layer, the dura. The meningeal lymphatics are directly connected to the peripheral lymphatic system in different mammalian species, including humans, and play a crucial role in preserving a "healthy" immune surveillance of the CNS, by shaping immune responses, not only locally at the meninges, but also at the level of the brain tissue. In this review, we will provide a comprehensive view on our current knowledge about the meningeal lymphatic vasculature, emphasizing its described roles in modulating CNS fluid and macromolecule drainage, meningeal and brain immunity, as well as glial and neuronal function in aging and in AD.

Meningioangiomatosis with Skull Erosion

Meningioangiomatosis (MA) is a rare, poorly studied brain hamartomatous lesion, the etiology of which is not fully elucidated. It typically involves the leptomeninges, extending to the underlying cortex, characterized by small vessel proliferation, perivascular cuffing, and scattered calcifications. Given its close proximity to, or direct involvement of, the cerebral cortex, MA lesions typically manifest in younger patients as recurrent episodes of refractory seizures, comprising approximately 0.6% of operated-on intractable epileptic lesions. Due to the absence of characteristic radiological features, MA lesions constitute a significant radiological challenge, making them easy to miss or misinterpret. Although MA lesions are rarely reported with still-unknown etiology, it is prudent to be aware of these lesions for prompt diagnosis and management to avoid morbidity and mortality associated with delayed diagnosis and treatment. We present a case of a young patient with a first-time seizure caused by a right parieto-occipital MA lesion that was successfully excised via an awake craniotomy, achieving 100% seizure control.

Dural and Leptomeningeal Diseases: Anatomy, Causes, and Neuroimaging Findings

Meningeal lesions can be caused by various conditions and pose diagnostic challenges. The authors review the anatomy of the meninges in the brain and spinal cord to provide a better understanding of the localization and extension of these diseases and summarize the clinical and imaging features of various conditions that cause dural and/or leptomeningeal enhancing lesions. These conditions include infectious meningitis (bacterial, tuberculous, viral, and fungal), autoimmune diseases (vasculitis, connective tissue diseases, autoimmune meningoencephalitis, Vogt-Koyanagi-Harada disease, neuro-Behçet syndrome, Susac syndrome, and sarcoidosis), primary and secondary tumors (meningioma, diffuse leptomeningeal glioneuronal tumor, melanocytic tumors, and lymphoma), tumorlike diseases (histiocytosis and immunoglobulin G4-related diseases), medication-induced diseases (immune-related adverse effects and posterior reversible encephalopathy syndrome), and other conditions (spontaneous intracranial hypotension, amyloidosis, and moyamoya disease). Although meningeal lesions may manifest with nonspecific imaging findings, correct diagnosis is important because the treatment strategy varies among these diseases. ©RSNA, 2023 Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article. Quiz questions for this article are available through the Online Learning Center.

Imaging of the meningeal lymphatic network in healthy adults: A 7T MRI study

BACKGROUND AND PURPOSE

Meningeal lymphatic vessels (MLVs) along the dural venous sinuses are suspected to be important in connecting the glymphatic and peripheral lymphatic system. Understanding the topography of MLVs may clarify the role of the glymphatic system in neurological diseases. The aim of this analysis was to use high resolution pre- and post-contrast FLAIR 7T MRI to identify and characterize the morphology of MLV in a cohort of healthy volunteers.

MATERIALS AND METHODS

MRI examinations of seventeen healthy volunteers enrolled as controls in a larger 7T MRI study were reviewed. Pre- and post-contrast 3-D FLAIR subtractions and MP2RAGE sequences were spatially normalized and reviewed for signal intensity and enhancement patterns within putative MLVs along pre-determined dural and venous structures. Frequency of occurrence of MLVs at the above-described locations and patterns of their enhancement were analyzed.

RESULTS

Putative MLVs are commonly located along the superior sagittal sinus (SSS) and cortical veins. A "fixed enhancement" signal pattern was more frequent at these locations (p<.05). The morphology of MLVs along the SSS qualitatively changes in an antero-posterior direction. Lack of signal was more frequent along the straight and transverse sinuses (p<.05).

CONCLUSION

Putative MLVs in healthy individuals are concentrated along the SSS and cortical veins. FLAIR signal and enhancement characteristics suggest these structures may transport proteinaceous fluid. Pathways connecting MLVs to cervical lymph nodes however remain unclear.

Primary meningeal central nervous system lymphoma: A case report and literature review

RATIONALE

Primary central nervous system lymphoma (PCNSL) is a rare extranodal non-Hodgkin lymphoma, and isolated meningeal PCNSL, without evidence of parenchymal involvement, is even less common, occurring in only 10% to 15% of cases.

PATIENT CONCERNS

A 65-years-old female presented to our hospital with progressive lower extremity motor dysfunction and blurred vision. The initial neurological examination revealed decreased muscle strength in both lower extremities and sensory dysfunction of lower extremities, saddle area, and buttocks. Brain magnetic resonance imaging showed no abnormalities. Lumbar enhanced magnetic resonance imaging showed T11 to L3 horizontal meningeal enhancement. Cerebrospinal fluid (CSF) cytology revealed lymphoma cells. Immunohistochemistry and flow cytometry of the CSF were performed as auxiliary methods to establish the diagnosis of lymphoma.

DIAGNOSES

The patient was diagnosed primary meningeal central nervous system lymphoma.

INTERVENTIONS

During hospitalization, the patient was treated with 2 courses of high-dose intrathecal methotrexate and rituximab combined with intrathecal chemotherapy and supportive treatment.

OUTCOMES

After 2 years of follow-up, the patient was able to walk and take care of herself.

LESSONS

Cases of PCNSL involving only the meninges are rare. Multimodal analysis of the CSF comprises an important component of the diagnostic work-up for patients with primary meningeal central nervous system lymphoma.

Recurrent meningeal malignant tumor: Assessment of differences in the solitary fibrous tumor/hemangiopericytoma spectrum through a case report

Solitary fibrous tumors (SFTs) are neoplasms that grow from mesenchymal fusiform cells. In the central nervous system, meninges are the common origin of these neoplasms. Although literature reports mostly SFT as benign neoplasm, malignancy data have been described in recurrences or metastatic lesions. Definitive diagnosis includes immunohistochemical profiles assessing cellular positivity for CD34, vimentin, CD99 and Bcl-2. Recent studies have demonstrated NAB2-STAT6 gene fusion as a distinct molecular feature of SFT with overexpression of the fusion protein NAB2-STAT6 in nuclei of these cells. Since several years, pathologists have grouped SFT and hemangiopericytomas (HPC) as different phenotypes of the same entity although both neoplasms do not share numerous features. This article, based on a case of a recurrent malignant SFT, aims to emphasize differences in the SFT/HPC spectrum due to the diagnostic, therapeutic and prognostic implications.

Single-cell profiling of human dura and meningioma reveals cellular meningeal landscape and insights into meningioma immune response

BACKGROUND

Recent investigations of the meninges have highlighted the importance of the dura layer in central nervous system immune surveillance beyond a purely structural role. However, our understanding of the meninges largely stems from the use of pre-clinical models rather than human samples.

METHODS

Single-cell RNA sequencing of seven non-tumor-associated human dura samples and six primary meningioma tumor samples (4 matched and 2 non-matched) was performed. Cell type identities, gene expression profiles, and T cell receptor expression were analyzed. Copy number variant (CNV) analysis was performed to identify putative tumor cells and analyze intratumoral CNV heterogeneity. Immunohistochemistry and imaging mass cytometry was performed on selected samples to validate protein expression and reveal spatial localization of select protein markers.

RESULTS

In this study, we use single-cell RNA sequencing to perform the first characterization of both non-tumor-associated human dura and primary meningioma samples. First, we reveal a complex immune microenvironment in human dura that is transcriptionally distinct from that of meningioma. In addition, we characterize a functionally diverse and heterogenous landscape of non-immune cells including endothelial cells and fibroblasts. Through imaging mass cytometry, we highlight the spatial relationship among immune cell types and vasculature in non-tumor-associated dura. Utilizing T cell receptor sequencing, we show significant TCR overlap between matched dura and meningioma samples. Finally, we report copy number variant heterogeneity within our meningioma samples.

CONCLUSIONS

Our comprehensive investigation of both the immune and non-immune cellular landscapes of human dura and meningioma at single-cell resolution builds upon previously published data in murine models and provides new insight into previously uncharacterized roles of human dura.

Recurrent IgG4-Related Meningeal Disease of the Cervicothoracic Spine: A Case Report and Review of the Literature

BACKGROUND

IgG4-related disease is a rare, recently recognized chronic inflammatory disease. IgG4-related hypertrophic pachymeningitis (IgG4-RHP) of the central nervous system predominantly involves the cranial meninges. Spinal involvement remains rare.

OBJECTIVE

We report a case of recurrent cervicothoracic IgG4-RHP and review the surgical literature.

METHODS AND MATERIALS

A 35-year-old woman presented with a 6-month history of neck and right shoulder pain, progressive right triceps weakness and paresthesias in the right C8 and T1 dermatomes. MRI demonstrated a T2 hypointense epidural soft tissue mass extending from C6-T1. The patient underwent C6-T1 laminoforaminotomy and partial resection with near complete symptom resolution. Histopathology was consistent with diagnosis of IgG4-RHP. Eighteen months postoperatively, she experienced symptom recurrence necessitating re-operation and adjuvant postoperative prednisone with complete resolution at 40-months' follow-up.

RESULTS AND CONCLUSIONS

Of the now nineteen confirmed cases of IgG4-RHP, fifteen underwent surgery. A majority achieved partial resection. Three surgical patients did not receive adjuvant therapy with symptomatic recurrence between 2 and 18 months.

Environmental Enrichment Induces Meningeal Niche Remodeling through TrkB-Mediated Signaling

Neural precursors (NPs) present in the hippocampus can be modulated by several neurogenic stimuli, including environmental enrichment (EE) acting through BDNF-TrkB signaling. We have recently identified NPs in meninges; however, the meningeal niche response to pro-neurogenic stimuli has never been investigated. To this aim, we analyzed the effects of EE exposure on NP distribution in mouse brain meninges. Following neurogenic stimuli, although we did not detect modification of the meningeal cell number and proliferation, we observed an increased number of neural precursors in the meninges. A lineage tracing experiment suggested that EE-induced β3-Tubulin⁺ immature neuronal cells present in the meninges originated, at least in part, from GLAST⁺ radial glia cells. To investigate the molecular mechanism responsible for meningeal reaction to EE exposure, we studied the BDNF-TrkB interaction. Treatment with ANA-12, a TrkB non-competitive inhibitor, abolished the EE-induced meningeal niche changes. Overall, these data showed, for the first time, that EE exposure induced meningeal niche remodeling through TrkB-mediated signaling. Fluoxetine treatment further confirmed the meningeal niche response, suggesting it may also respond to other pharmacological neurogenic stimuli. A better understanding of the neurogenic stimuli modulation for meninges may be useful to improve the effectiveness of neurodegenerative and neuropsychiatric treatments.

Changes in Cerebrospinal Fluid Balance of TNF and TNF Receptors in Naïve Multiple Sclerosis Patients: Early Involvement in Compartmentalised Intrathecal Inflammation

An imbalance of TNF signalling in the inflammatory milieu generated by meningeal immune cell infiltrates in the subarachnoid space in multiple sclerosis (MS), and its animal model may lead to increased cortical pathology. In order to explore whether this feature may be present from the early stages of MS and may be associated with the clinical outcome, the protein levels of TNF, sTNF-R1 and sTNF-R2 were assayed in CSF collected from 122 treatment-naïve MS patients and 36 subjects with other neurological conditions at diagnosis. Potential correlations with other CSF cytokines/chemokines and with clinical and imaging parameters at diagnosis (T0) and after 2 years of follow-up (T24) were evaluated. Significantly increased levels of TNF (fold change: 7.739; p < 0.001), sTNF-R1 (fold change: 1.693; p < 0.001) and sTNF-R2 (fold change: 2.189; p < 0.001) were detected in CSF of MS patients compared to the control group at T0. Increased TNF levels in CSF were significantly (p < 0.01) associated with increased EDSS change (r = 0.43), relapses (r = 0.48) and the appearance of white matter lesions (r = 0.49). CSF levels of TNFR1 were associated with cortical lesion volume (r = 0.41) at T0, as well as with new cortical lesions (r = 0.56), whilst no correlation could be found between TNFR2 levels in CSF and clinical or MRI features. Combined correlation and pathway analysis (ingenuity) of the CSF protein pattern associated with TNF expression (encompassing elevated levels of BAFF, IFN-γ, IL-1β, IL-10, IL-8, IL-16, CCL21, haptoglobin and fibrinogen) showed a particular relationship to the interaction between innate and adaptive immune response. The CSF sTNF-R1-associated pattern (encompassing high levels of CXCL13, TWEAK, LIGHT, IL-35, osteopontin, pentraxin-3, sCD163 and chitinase-3-L1) was mainly related to altered T cell and B cell signalling. Finally, the CSF TNFR2-associated pattern (encompassing high CSF levels of IFN-β, IFN-λ2, sIL-6Rα) was linked to Th cell differentiation and regulatory cytokine signalling. In conclusion, dysregulation of TNF and TNF-R1/2 pathways associates with specific clinical/MRI profiles and can be identified at a very early stage in MS patients, at the time of diagnosis, contributing to the prediction of the disease outcome.

Meningeal B Cell Clusters Correlate with Submeningeal Pathology in a Natural Model of Multiple Sclerosis

Multiple sclerosis (MS) is an idiopathic demyelinating disease in which meningeal inflammation correlates with accelerated disease progression. The study of meningeal inflammation in MS has been limited because of constrained access to MS brain/spinal cord specimens and the lack of experimental models recapitulating progressive MS. Unlike induced models, a spontaneously occurring model would offer a unique opportunity to understand MS immunopathogenesis and provide a compelling framework for translational research. We propose granulomatous meningoencephalomyelitis (GME) as a natural model to study neuropathological aspects of MS. GME is an idiopathic, progressive neuroinflammatory disease of young dogs with a female bias. In the GME cases examined in this study, the meninges displayed focal and disseminated leptomeningeal enhancement on magnetic resonance imaging, which correlated with heavy leptomeningeal lymphocytic infiltration. These leptomeningeal infiltrates resembled tertiary lymphoid organs containing large B cell clusters that included few proliferating Ki67+ cells, plasma cells, follicular dendritic/reticular cells, and germinal center B cell-like cells. These B cell collections were confined in a specialized network of collagen fibers associated with the expression of the lympho-organogenic chemokines CXCL13 and CCL21. Although neuroparenchymal perivascular infiltrates contained B cells, they lacked the immune signature of aggregates in the meningeal compartment. Finally, meningeal B cell accumulation correlated significantly with cortical demyelination reflecting neuropathological similarities to MS. Hence, during chronic neuroinflammation, the meningeal microenvironment sustains B cell accumulation that is accompanied by underlying neuroparenchymal injury, indicating GME as a novel, naturally occurring model to study compartmentalized neuroinflammation and the associated pathology thought to contribute to progressive MS.

Medulloblastoma uses GABA transaminase to survive in the cerebrospinal fluid microenvironment and promote leptomeningeal dissemination

Medulloblastoma (MB) is a malignant pediatric brain tumor arising in the cerebellum. Although abnormal GABAergic receptor activation has been described in MB, studies have not yet elucidated the contribution of receptor-independent GABA metabolism to MB pathogenesis. We find primary MB tumors globally display decreased expression of GABA transaminase (ABAT), the protein responsible for GABA metabolism, compared with normal cerebellum. However, less aggressive WNT and SHH subtypes express higher ABAT levels compared with metastatic G3 and G4 tumors. We show that elevated ABAT expression results in increased GABA catabolism, decreased tumor cell proliferation, and induction of metabolic and histone characteristics mirroring GABAergic neurons. Our studies suggest ABAT expression fluctuates depending on metabolite changes in the tumor microenvironment, with nutrient-poor conditions upregulating ABAT expression. We find metastatic MB cells require ABAT to maintain viability in the metabolite-scarce cerebrospinal fluid by using GABA as an energy source substitute, thereby facilitating leptomeningeal metastasis formation.

Meningeal inflammation in multiple sclerosis induces phenotypic changes in cortical microglia that differentially associate with neurodegeneration

Meningeal inflammation strongly associates with demyelination and neuronal loss in the underlying cortex of progressive MS patients, thereby contributing significantly to clinical disability. However, the pathological mechanisms of meningeal inflammation-induced cortical pathology are still largely elusive. By extensive analysis of cortical microglia in post-mortem progressive MS tissue, we identified cortical areas with two MS-specific microglial populations, termed MS1 and MS2 cortex. The microglial population in MS1 cortex was characterized by a higher density and increased expression of the activation markers HLA class II and CD68, whereas microglia in MS2 cortex showed increased morphological complexity and loss of P2Y12 and TMEM119 expression. Interestingly, both populations associated with inflammation of the overlying meninges and were time-dependently replicated in an in vivo rat model for progressive MS-like chronic meningeal inflammation. In this recently developed animal model, cortical microglia at 1-month post-induction of experimental meningeal inflammation resembled microglia in MS1 cortex, and microglia at 2 months post-induction acquired a MS2-like phenotype. Furthermore, we observed that MS1 microglia in both MS cortex and the animal model were found closely apposing neuronal cell bodies and to mediate pre-synaptic displacement and phagocytosis, which coincided with a relative sparing of neurons. In contrast, microglia in MS2 cortex were not involved in these synaptic alterations, but instead associated with substantial neuronal loss. Taken together, our results show that in response to meningeal inflammation, microglia acquire two distinct phenotypes that differentially associate with neurodegeneration in the progressive MS cortex. Furthermore, our in vivo data suggests that microglia initially protect neurons from meningeal inflammation-induced cell death by removing pre-synapses from the neuronal soma, but eventually lose these protective properties contributing to neuronal loss.

Inflammatory Regulation of CNS Barriers After Traumatic Brain Injury: A Tale Directed by Interleukin-1

Several barriers separate the central nervous system (CNS) from the rest of the body. These barriers are essential for regulating the movement of fluid, ions, molecules, and immune cells into and out of the brain parenchyma. Each CNS barrier is unique and highly dynamic. Endothelial cells, epithelial cells, pericytes, astrocytes, and other cellular constituents each have intricate functions that are essential to sustain the brain's health. Along with damaging neurons, a traumatic brain injury (TBI) also directly insults the CNS barrier-forming cells. Disruption to the barriers first occurs by physical damage to the cells, called the primary injury. Subsequently, during the secondary injury cascade, a further array of molecular and biochemical changes occurs at the barriers. These changes are focused on rebuilding and remodeling, as well as movement of immune cells and waste into and out of the brain. Secondary injury cascades further damage the CNS barriers. Inflammation is central to healthy remodeling of CNS barriers. However, inflammation, as a secondary pathology, also plays a role in the chronic disruption of the barriers' functions after TBI. The goal of this paper is to review the different barriers of the brain, including (1) the blood-brain barrier, (2) the blood-cerebrospinal fluid barrier, (3) the meningeal barrier, (4) the blood-retina barrier, and (5) the brain-lesion border. We then detail the changes at these barriers due to both primary and secondary injury following TBI and indicate areas open for future research and discoveries. Finally, we describe the unique function of the pro-inflammatory cytokine interleukin-1 as a central actor in the inflammatory regulation of CNS barrier function and dysfunction after a TBI.

Neuropathological correlates of cortical superficial siderosis in cerebral amyloid angiopathy

Cortical superficial siderosis is an established haemorrhagic neuroimaging marker of cerebral amyloid angiopathy. In fact, cortical superficial siderosis is emerging as a strong independent risk factor for future lobar intracerebral haemorrhage. However, the underlying neuropathological correlates and pathophysiological mechanisms of cortical superficial siderosis remain elusive. Here we use an in vivo MRI, ex vivo MRI, histopathology approach to assess the neuropathological correlates and vascular pathology underlying cortical superficial siderosis. Fourteen autopsy cases with cerebral amyloid angiopathy (mean age at death 73 years, nine males) and three controls (mean age at death 91 years, one male) were included in the study. Intact formalin-fixed cerebral hemispheres were scanned on a 3 T MRI scanner. Cortical superficial siderosis was assessed on ex vivo gradient echo and turbo spin echo MRI sequences and compared to findings on available in vivo MRI. Subsequently, 11 representative areas in four cases with available in vivo MRI scans were sampled for histopathological verification of MRI-defined cortical superficial siderosis. In addition, samples were taken from predefined standard areas of the brain, blinded to MRI findings. Serial sections were stained for haematoxylin and eosin and Perls' Prussian blue, and immunohistochemistry was performed against amyloid-β and GFAP. Cortical superficial siderosis was present on ex vivo MRI in 8/14 cases (57%) and 0/3 controls (P = 0.072). Histopathologically, cortical superficial siderosis corresponded to iron-positive haemosiderin deposits in the subarachnoid space and superficial cortical layers, indicative of chronic bleeding events originating from the leptomeningeal vessels. Increased severity of cortical superficial siderosis was associated with upregulation of reactive astrocytes. Next, cortical superficial siderosis was assessed on a total of 65 Perls'-stained sections from MRI-targeted and untargeted sampling combined in cerebral amyloid angiopathy cases. Moderate-to-severe cortical superficial siderosis was associated with concentric splitting of the vessel wall (an advanced form of cerebral amyloid angiopathy-related vascular damage) in leptomeningeal vessels (P < 0.0001), but reduced cerebral amyloid angiopathy severity in cortical vessels (P = 0.048). In terms of secondary tissue injury, moderate-to-severe cortical superficial siderosis was associated with the presence of microinfarcts (P = 0.025), though not microbleeds (P = 0.973). Collectively, these data suggest that cortical superficial siderosis on MRI corresponds to iron-positive deposits in the superficial cortical layers, representing the chronic manifestation of bleeding episodes from leptomeningeal vessels. Cortical superficial siderosis appears to be the result of predominantly advanced cerebral amyloid angiopathy of the leptomeningeal vessels and may trigger secondary ischaemic injury in affected areas.

Leptomeningeal relapse in primary cutaneous DLBCL: Implications for a prophylactic CNS therapy

BACKGROUND

Isolated leptomeningeal relapse in a case of cutaneous lymphoma is an uncommon event more so in a case of primary cutaneous diffuse large B-cell lymphoma (PCDLBCL). This phenomenon is of great significance as the subsequent prognosis becomes poor and the prophylactic central nervous system (CNS) therapy if administered, can reduce the chances of relapse, however, the survival benefit remains uncertain. The role of prophylactic CNS therapy is not well defined in the case of PCDLBCL.

CASE

We report a case of PCDLBCL leg type with a low CNS International Prognostic Index (CNS-IPI) risk, who developed isolated leptomeningeal relapse in the form of bilateral facial nerve palsy. He was managed by 2nd line chemotherapy and CNS directed therapy and achieved complete remission.

CONCLUSION

PCDLBCL leg type is an aggressive malignancy. Molecular/genomic mechanism likely responsible for CNS dissemination should be identified by prospective multi-centric studies that can better define the subsets of patients eligible for prophylactic therapy in the absence of a high CNS-IPI risk.

-----Comparison of T1-Post and FLAIR-Post MRI for identification of traumatic meningeal enhancement in traumatic brain injury patients

Traumatic meningeal enhancement (TME) is a novel biomarker observed on post-contrast fluid-attenuated inversion recovery (FLAIR) in patients who undergo contrast-enhanced magnetic resonance imaging (MRI) after suspected traumatic brain injury (TBI). TME may be seen on acute MRI despite the absence of other trauma-related intracranial findings. In this study we compare conspicuity of TME on FLAIR post-contrast and T1 weighted imaging (T1WI) post-contrast, and investigate if TME is best detected by FLAIR post-contrast or T1WI post-contrast sequences. Subjects selected for analysis enrolled in the parent study (NCT01132937) in 2016 and underwent contrast-enhanced MRI within 48 hours of suspected TBI. Two blinded readers reviewed pairs of pre- and post-contrast T1WI and FLAIR images for presence or absence of TME. Discordant pairs between the two blinded readers were reviewed by a third reader. Cohen's kappa coefficient was used to calculate agreement. Twenty-five subjects (15 males, 10 females; median age 48 (Q1:35-Q3:62; IQR: 27)) were included. The blinded readers had high agreement for presence of TME on FLAIR (Kappa of 0.90), but had no agreement for presence of TME on T1WI (Kappa of -0.24). The FLAIR and T1WI scans were compared among all three readers and 62% of the cases positive on FLAIR could be seen on T1WI. However, 38% of the cases who were read positive on FLAIR for TME were read negative for TME on T1WI. Conspicuity of TME is higher on post-contrast FLAIR MRI than on post-contrast T1WI. TME as seen on post-contrast FLAIR MRI can aid in the identification of patients with TBI.

B cell rich meningeal inflammation associates with increased spinal cord pathology in multiple sclerosis

Increased inflammation in the cerebral meninges is associated with extensive subpial cortical grey matter pathology in the forebrain and a more severe disease course in a substantial proportion of secondary progressive multiple sclerosis (SPMS) cases. It is not known whether this relationship extends to spinal cord pathology. We assessed the contribution of meningeal and parenchymal immune infiltrates to spinal cord pathology in SPMS cases characterized in the presence (F+) or absence (F-) of lymphoid-like structures in the forebrain meninges. Transverse cryosections of cervical, thoracic and lumbar cord of 22 SPMS and five control cases were analyzed for CD20+ B cells, CD4+ and CD8+ T cells, microglia/macrophages (IBA-1+), demyelination (myelin oligodendrocyte glycoprotein+) and axon density (neurofilament-H+). Lymphoid-like structures containing follicular dendritic cell networks and dividing B cells were seen in the spinal meninges of 3 out of 11 F+ SPMS cases. CD4+ and CD20+ cell counts were increased in F+ SPMS compared to F- SPMS and controls, whilst axon loss was greatest in motor and sensory tracts of the F+ SPMS cases (P < 0.01). The density of CD20+ B cells of the spinal leptomeninges correlated with CD4+ T cells and total B and T cells of the meninges; with the density of white matter perivascular CD20+ and CD4+ lymphocytes (P < 0.05); with white matter lesion area (P < 0.05); and the extent of axon loss (P < 0.05) in F+ SPMS cases only. We show that the presence of lymphoid-like structures in the forebrain is associated with a profound spinal cord pathology and local B cell rich meningeal inflammation associates with the extent of cord pathology. Our work supports a principal role for B cells in sustaining inflammation and tissue injury throughout the CNS in the progressive disease stage.

Proteomics pinpoints alterations in grade I meningiomas of male versus female patients

Meningiomas are among the most common primary tumors of the central nervous system (CNS) and originate from the arachnoid or meningothelial cells of the meninges. Surgery is the first option of treatment, but depending on the location and invasion patterns, complete removal of the tumor is not always feasible. Reports indicate many differences in meningiomas from male versus female patients; for example, incidence is higher in females, whereas males usually develop the malignant and more aggressive type. With this as motivation, we used shotgun proteomics to compare the proteomic profile of grade I meningioma biopsies of male and female patients. Our results listed several differentially abundant proteins between the two groups; some examples are S100-A4 and proteins involved in RNA splicing events. For males, we identified enriched pathways for cell-matrix organization and for females, pathways related to RNA transporting and processing. We believe our findings contribute to the understanding of the molecular differences between grade I meningiomas of female and male patients.

Structural and functional conservation of non-lumenized lymphatic endothelial cells in the mammalian leptomeninges

The vertebrate CNS is surrounded by the meninges, a protective barrier comprised of the outer dura mater and the inner leptomeninges, which includes the arachnoid and pial layers. While the dura mater contains lymphatic vessels, no conventional lymphatics have been found within the brain or leptomeninges. However, non-lumenized cells called Brain/Mural Lymphatic Endothelial Cells or Fluorescent Granule Perithelial cells (muLECs/BLECs/FGPs) that share a developmental program and gene expression with peripheral lymphatic vessels have been described in the meninges of zebrafish. Here we identify a structurally and functionally similar cell type in the mammalian leptomeninges that we name Leptomeningeal Lymphatic Endothelial Cells (LLEC). As in zebrafish, LLECs express multiple lymphatic markers, containing very large, spherical inclusions, and develop independently from the meningeal macrophage lineage. Mouse LLECs also internalize macromolecules from the cerebrospinal fluid, including Amyloid-β, the toxic driver of Alzheimer's disease progression. Finally, we identify morphologically similar cells co-expressing LLEC markers in human post-mortem leptomeninges. Given that LLECs share molecular, morphological, and functional characteristics with both lymphatics and macrophages, we propose they represent a novel, evolutionary conserved cell type with potential roles in homeostasis and immune organization of the meninges.

Meningeal Lymphatic Pathway of Brain Clearing From the Blood After Haemorrhagic Injuries

This seems to be the time to gain new knowledge about the meningeal lymphatic system and a deeper understanding of its anatomy and physiology. Although it is known that the meningeal lymphatics present in the layers of the brain, limited information is available about the role of this system in brain function. Here, for the first time we clearly demonstrate that the meningeal lymphatic pathway is involved in brain clearing from the blood after intracranial hemorrhage associated with hypoxia and forms a connective bridge between interstitial, cerebral spinal fluid and peripheral lymphatics. We also show that the development of methods to stimulate meningeal lymph flow after hemorrhagic evidence in the brain might be a neuroprotective strategy for effective recovery of the brain after a cerebrovascular catastrophe.

Radiological and clinical findings of isolated meningeal Rosai-Dorfman disease of the central nervous system

Rosai-Dorfman disease (RDD) with isolated central nervous system (CNS) involvement is an extremely rare disease. Most RDD of the CNS present as dural-based mass mimicking meningioma and other common lesions, which makes preoperative accurate diagnosis of great difficulty. We searched the pathology database in our hospital and 3 cases of RDD with isolated CNS involvement were finally included in our study. Radiological and clinical findings of these three cases were retrospectively analyzed. The lesions of 2 cases were dura-based against the cerebral convexity, presenting as a sheet-shaped thickened dura mater, another case was located just across the cerebral falx, the dural display in the center was intact. The 3 cases showed low signal intensity on T2-weighted image, obviously enhanced, significantly surrounding edema and finger-like protuberance but no invasion of the brain parenchyma or no sign of hyperplasia or sclerosis of the surrounding cranial bones. In conclusion, when we come across a disease that mimicking meningioma, especially when it manifests as the above radiological features, we should considered it might be a kind of proliferative disease of the meninges, such as RDD.

Meningeal Architecture of the Jugular Foramen: An Anatomic Study Using Plastinated Histologic Sections

OBJECTIVE

This 3-dimensional histologic study aimed to provide a precise description of the meningeal structures in the jugular foramen.

METHODS

22 posterior skull base tissue blocks containing the jugular foramen region were obtained from 11 human cadaveric heads. These blocks were plastinated and cut into serial sections. After staining, these sections were examined under an optical microscope and used to reconstruct a 3-dimensional visualization model.

RESULTS

At the intracranial orifice of the jugular foramen, the meningeal dura formed 2 separate dural perforations: the glossopharyngeal meatus and the vagal meatus. The arachnoid extended into 2 dural meatuses and terminated at the inferior ganglion of the glossopharyngeal nerve in the glossopharyngeal meatus and the superior ganglion of the vagus nerve in the vagal meatus. At the intraforaminal part of the jugular foramen, the meningeal dura encased the glossopharyngeal nerve to form a dural sheath while encasing the vagus and accessory nerves to form a dural network. At the extracranial orifice of the jugular foramen, the dural wall of the jugular bulb extended downward to form a dense connective tissue sheath. The initial end of the internal jugular vein invaginated into this sheath and fused with the jugular bulb.

CONCLUSIONS

Knowledge of the anatomy of the meningeal architecture of the jugular foramen can be helpful in avoiding surgical complications of the lower cranial nerves when this complex area is approached.

Characterization of leptomeningeal inflammation in rodent experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis

BACKGROUND

Leptomeningeal inflammation, as evidenced by leptomeningeal contrast enhancement (LMCE), is associated to cortical pathology in multiple sclerosis. The temporal pattern of LMCE in experimental autoimmune encephalomyelitis (EAE) myelin oligodendrocyte glycoprotein (MOG) is unknown.

OBJECTIVE

To investigate LMCE using serial MRI in the EAE model of MS, and its association with clinical disease progression. To characterize the relationship between LMCE and underlying histological correlates.

DESIGN

Thirteen C57BL/6J mice, MOG-immunized (35-55 amino acid) and 8 saline injected animals were assessed at pre-induction and at 3, 6, 10, 20, 27, 32, 45 and 63 days post induction (dPI). LMCE scan was obtained using FLAIR-RARE sequence after post-contrast gadolinium administration on 9.4 T scanner. Brain cryo-sections were assessed for measuring cellular density of Iba1 positive macrophage/microglia at 10 dPI and 32 dPI, and for the presence of T, B and macrophage cells in the meningeal layer at 10 dPI and 63 dPI.

RESULTS

All EAE-MOG animals showed presence of LMCE and none of the control mice. The peak signal intensity of LMCE was evidenced at 10dPI in the meninges and decreased through 10-63 dPI. The peak of LMCE was associated with a weight loss starting at 1 week PI and with clinical symptoms starting at 2 weeks PI. Histological analysis of the brain tissue showed a higher density of Iba1 positive microglial cells in the EAE-MOG animals, corresponding to the areas of LMCE. Meninges of EAE mice showed higher density of Iba1 stained macrophage cells relative to saline animals. EAE animals also showed the presence of T and B cells in the meninges which were absent in the saline animals.

CONCLUSIONS

LMCE peak intensity in the meninges corresponds to the acute inflammatory phase of EAE-MOG disease progression, and is associated with clinical symptoms and higher inflammatory cell density.

Huge multiple spinal extradural meningeal cysts in infancy

BACKGROUND

Multiple spinal extradural meningeal cysts (SEMCs) are rare lesions. SEMCs communicate with the subarachnoid space through multiple dural defects and expand into the extradural space with progressive spinal cord compression.

CASE PRESENTATION

We report a 5-month-old boy with hydronephrosis involving nine huge SEMCs that were distributed from the T1-L5 levels. Eight SEMCs, except for one small noncommunicating cyst, were exposed through laminoplastic laminotomy at the T10-L5 and T3-5 levels. Five transdural communications with dural defects were packed with a piece of autologous muscle and fibrin glue. Tenting sutures to lift up the dura to the vertebral arch were added to minimize the extradural dead space. Postoperatively, cord compression was relieved and hydronephrosis improved.

CONCLUSION

In conclusion, packing of all dural defects and dural tenting sutures at a one-staged operation is useful in the surgical management of huge and multiple SEMCs in infancy.

Vanishing diffuse leptomeningeal contrast enhancement in an infant with choroid plexus papilloma

Choroid plexus tumors (CPT) can present in the baseline magnetic resonance imaging (MRI) with lesions compatible with leptomeningeal dissemination. Therapeutic strategy in this condition is controversial. We present a case of an infant with CPP and significant diffuse leptomeningeal contrast enhancement at diagnosis, which spontaneously resolved after removal of the primary tumor. In these challenging cases, several aspects, such as histopathological/molecular diagnosis and close radiological follow-up, should be taken into account to avoid unnecessary treatments.

Continuous and bolus intraventricular topotecan prolong survival in a mouse model of leptomeningeal medulloblastoma

Leptomeningeal metastasis remains a difficult clinical challenge. Some success has been achieved by direct administration of therapeutics into the cerebrospinal fluid (CSF) circumventing limitations imposed by the blood brain barrier. Here we investigated continuous infusion versus bolus injection of therapy into the CSF in a preclinical model of human Group 3 medulloblastoma, the molecular subgroup with the highest incidence of leptomeningeal disease. Initial tests of selected Group 3 human medulloblastoma cell lines in culture showed that D283 Med and D425 Med were resistant to cytosine arabinoside and methotrexate. D283 Med cells were also resistant to topotecan, whereas 1 μM topotecan killed over 99% of D425 Med cells. We therefore introduced D425 Med cells, modified to express firefly luciferase, into the CSF of immunodeficient mice. Mice were then treated with topotecan or saline in five groups: continuous intraventricular (IVT) topotecan via osmotic pump (5.28 μg/day), daily bolus IVT topotecan injections with a similar daily dose (6 μg/day), systemic intraperitoneal injections of a higher daily dose of topotecan (15 μg/day), daily IVT pumped saline and daily intraperitoneal injections of saline. Bioluminescence analyses revealed that both IVT topotecan treatments effectively slowed leptomeningeal tumor growth in the brains. Histological analysis showed that they were associated with localized brain necrosis, possibly due to backtracking of topotecan around the catheter. In the spines, bolus IVT topotecan showed a trend towards slower tumor growth compared to continuous (pump) IVT topotecan, as measured by bioluminescence. Both continuous and bolus topotecan IVT showed longer survival compared to other groups. Thus, both direct IVT topotecan CSF delivery methods produced better anti-medulloblastoma effect compared to systemic therapy at the dosages used here.

CNS lymphatic drainage and neuroinflammation are regulated by meningeal lymphatic vasculature

Neuroinflammatory diseases, such as multiple sclerosis, are characterized by invasion of the brain by autoreactive T cells. The mechanism for how T cells acquire their encephalitogenic phenotype and trigger disease remains, however, unclear. The existence of lymphatic vessels in the meninges indicates a relevant link between the CNS and peripheral immune system, perhaps affecting autoimmunity. Here we demonstrate that meningeal lymphatics fulfill two critical criteria: they assist in the drainage of cerebrospinal fluid components and enable immune cells to enter draining lymph nodes in a CCR7-dependent manner. Unlike other tissues, meningeal lymphatic endothelial cells do not undergo expansion during inflammation, and they express a unique transcriptional signature. Notably, the ablation of meningeal lymphatics diminishes pathology and reduces the inflammatory response of brain-reactive T cells during an animal model of multiple sclerosis. Our findings demonstrate that meningeal lymphatics govern inflammatory processes and immune surveillance of the CNS and pose a valuable target for therapeutic intervention.

Intracranial, extraneural ectopic lymph node in a bovine (Bos taurus)

The brain from a field necropsied 8-month-old feedlot heifer presenting with an acute history of depression, lethargy, dyspnoea and anorexia was evaluated grossly and by histopathology. The meninges overlying the left cerebral hemisphere contained a 12 × 26 × 32 mm, dark red, soft, ovoid mass. Histologic examination of this tissue revealed a well-organized lymph node with normal architecture. Organization of reactive lymphoid tissue resembling normal lymph node architecture may occur under chronic stimulation. However, there are no known aggregates of lymphoid tissue present within the cranial vault in any veterinary species. This is the first reported case of an intracranial ectopic lymph node in any species.

Tumor-to-Lesion Metastasis: Case Report of Carcinoma Metastasis to Multiple Sclerosis Lesion

BACKGROUND

The term "tumor-to-lesion metastasis" is an extension of "tumor-to-tumor metastasis," which is a rare but well-documented phenomenon. Tumor metastasis to the meninges and/or central nervous system (CNS) is rare in patents with multiple sclerosis (MS), although MS lesions bear many similarities to the primary tumor microenvironment and metastatic niche. We present the first case of malignant tumor metastasis to MS lesions with immunophenotyping of inflammatory cells in the metastatic foci.

CASE DESCRIPTION

A 45-year-old male patient with a 6-year history of MS and newly diagnosed lung carcinoma developed carcinoma metastases in the meninges and CNS, as well as into mixed active/inactive MS lesions. The carcinoma-hosting MS lesions exhibited abundant macrophages/microglia with ongoing demyelination but rare T cells. In comparison, a 46-year-old female patient with a 21-month history of MS and newly diagnosed gastric carcinoma was found to have leptomeningeal carcinomatosis and separate active MS lesions containing not only frequent macrophages/microglia but also T cells.

CONCLUSIONS

The carcinoma-hosting MS lesions are unlike typical active lesions but recapitulate the CNS metastatic niche. Our observations suggest that metastasis-hosting MS lesions might require a distinct immune microenvironment to be permissive to the seeding and growth of metastatic tumors.

Evaluation of Leptomeningeal Contrast Enhancement Using Pre-and Postcontrast Subtraction 3D-FLAIR Imaging in Multiple Sclerosis

BACKGROUND AND PURPOSE

Leptomeningeal contrast enhancement is found in patients with multiple sclerosis, though reported rates have varied. The use of 3D-fluid-attenuated inversion recovery pre- and postcontrast subtraction imaging may more accurately determine the frequency of leptomeningeal contrast enhancement. The purpose of this study was to investigate the frequency of leptomeningeal contrast enhancement using the pre- and postcontrast subtraction approach and to evaluate 3 different methods of assessing the presence of leptomeningeal contrast enhancement.

MATERIALS AND METHODS

We enrolled 258 consecutive patients with MS (212 with relapsing-remitting MS, 32 with secondary-progressive MS, and 14 with clinically isolated syndrome) who underwent both pre- and 10-minute postcontrast 3D-FLAIR sequences after a single dose of gadolinium injection on 3T MR imaging. The analysis included leptomeningeal contrast-enhancement evaluation on 3D-FLAIR postcontrast images in native space (method A), on pre- and postcontrast 3D-FLAIR images in native space (method B), and on pre-/postcontrast 3D-FLAIR coregistered and subtracted images (method C, used as the criterion standard).

RESULTS

In total, 51 (19.7%) patients with MS showed the presence of leptomeningeal contrast enhancement using method A; 39 (15.1%), using method B; and 39 (15.1%), using method C (P = .002). Compared with method C as the criterion standard, method A showed 89.8% sensitivity and 92.7% specificity, while method B showed 84.6% sensitivity and 97.3% specificity (P < .001) at the patient level. Reproducibility was the highest using method C (κ agreement, r = 088, P < .001). The mean time to analyze the 3D-FLAIR images was significantly lower with method C compared with methods A and B (P < .001).

CONCLUSIONS

3D-FLAIR postcontrast imaging offers a sensitive method for detecting leptomeningeal contrast enhancement in patients with MS. However, the use of subtraction imaging helped avoid false-positive cases, decreased reading time, and increased the accuracy of leptomeningeal contrast-enhancement foci detection in a clinical routine.

Visualization of neuritic plaques in Alzheimer's disease by polarization-sensitive optical coherence microscopy

One major hallmark of Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA) is the deposition of extracellular senile plaques and vessel wall deposits composed of amyloid-beta (Aβ). In AD, degeneration of neurons is preceded by the formation of Aβ plaques, which show different morphological forms. Most of them are birefringent owing to the parallel arrangement of amyloid fibrils. Here, we present polarization sensitive optical coherence microscopy (PS-OCM) for imaging mature neuritic Aβ plaques based on their birefringent properties. Formalin-fixed, post-mortem brain samples of advanced stage AD patients were investigated. In several cortical brain regions, neuritic Aβ plaques were successfully visualized in tomographic and three-dimensional (3D) images. Cortical grey matter appeared polarization preserving, whereas neuritic plaques caused increased phase retardation. Consistent with the results from PS-OCM imaging, the 3D structure of senile Aβ plaques was computationally modelled for different illumination settings and plaque sizes. Furthermore, the birefringent properties of cortical and meningeal vessel walls in CAA were investigated in selected samples. Significantly increased birefringence was found in smaller vessels. Overall, these results provide evidence that PS-OCM is able to assess amyloidosis based on intrinsic birefringent properties.

Meningeal Preservation in a Child Mummy from Ancient Egypt

Over many centuries, the ancient Egyptians developed a method of preserving bodies so they would remain lifelike. Mummification of bodies was originally a natural process in Egypt, and it evolved to a sophisticated embalming system to preserve the individual for the afterlife. Afterwards, mummification continued to be practiced in Egypt for some 3000 years, lasting until the end of the Christian era. In the Coptic necropolis of Qarara (Middle Egypt), 17 mummified individuals were studied during the 2012 campaign. One of them was a 6-8 old-year male child with a damaged skull that allowed us to see the meningeal structures covering the entire cranial vault, in absence of brain remains. This finding in a child mummy is exceptional, as reflected in the specialized literature.

Isolated neurosarcoidosis – MR findings and pathologic correlation: A case report

Neurosarcoidosis is a diagnostic challenge, especially if systemic symptoms are absent. We present a 49-year-old woman with isolated neurosarcoidosis. The main symptom was loss of vision in the left eye. Brain MR imaging showed 6 high-signal white matter lesions frontotemporally on proton density and T2-weighted turbo spin-echo images. Coronal fat-saturated turbo FLAIR images of the orbits showed a swollen left optic nerve with increased signal intensity, which finding has not been previously published in sarcoid optic neuropathy. A control MR examination showed meningeal enhancement of the left optic nerve and leptomeningeal enhancing lesions around the brain stem. Spinal MR revealed leptomeningeal enhancement throughout the spinal cord and asymptomatic enhancing cauda equina lesions, mimicking subarachnoid tumour seeding, and an enhancing nerve root mass at Th12/L1. Biopsy of the latter lesion revealed non-caseating granulomas consistent with sarcoidosis.

Cytokeratin-Positive Meningeal Peripheral PNET/Ewing's Sarcoma of the Cervical Spinal Cord: Diagnostic Value of Genetic Analysis

Peripheral primitive neuroectodermal tumor (PNET)/Ewing's sarcoma (ES) of the central nervous system is extremely rare and should be differentiated from central PNET and other small blue round cell tumors. We describe a case of a meningeal peripheral PNET/ES of the spinal cord in an 11 -year-old boy. Immunohistochemically, the small blue round cell tumor showed expression of epithelial markers and of CD99, thus posing an important differential diagnostic problem with a poorly differentiated synovial sarcoma. Fluorescence in situ hybridization revealed rearrangement of the EWS gene, as seen in peripheral PNET/ES. Peripheral PNET/ES does occur in the central nervous system, but its diagnosis can be extremely difficult on morphologic and immunohistochemical grounds alone. Genetic analysis plays a key role in its distinction from other small blue round cell tumors.

Inflammation Caused by Praziquantel Treatment Depends on the Location of the Taenia solium Cysticercus in Porcine Neurocysticercosis

Background

Neurocysticercosis (NCC), infection of the central nervous system by Taenia solium cysticerci, is a pleomorphic disease. Inflammation around cysticerci is the major cause of disease but is variably present. One factor modulating the inflammatory responses may be the location and characteristics of the brain tissue adjacent to cysticerci. We analyzed and compared the inflammatory responses to cysticerci located in the parenchyma to those in the meninges or cysticerci partially in contact with both the parenchyma and the meninges (corticomeningeal).

Methodology/Principal Findings

Histological specimens of brain cysticerci (n = 196) from 11 pigs naturally infected with Taenia solium cysticerci were used. Four pigs were sacrificed after 2 days and four after 5 days of a single dose of praziquantel; 3 pigs did not receive treatment. All pigs were intravenously injected with Evans Blue to assess disruption of the blood-brain barrier. The degree of inflammation was estimated by use of a histological score (ISC) based on the extent of the inflammation in the pericystic areas as assessed in an image composed of several photomicrographs taken at 40X amplification. Parenchymal cysticerci provoked a significantly greater level of pericystic inflammation (higher ISC) after antiparasitic treatment compared to meningeal and corticomeningeal cysticerci. ISC of meningeal cysticerci was not significantly affected by treatment. In corticomeningeal cysticerci, the increase in ISC score was correlated to the extent of the cysticercus adjacent to the brain parenchyma. Disruption of the blood-brain barrier was associated with treatment only in parenchymal tissue.

Significance

Inflammatory response to cysticerci located in the meninges was significantly decreased compared to parenchymal cysticerci. The suboptimal inflammatory response to cysticidal drugs may be the reason subarachnoid NCC is generally refractory to treatment compared to parenchymal NCC.

The cystic larvae of the pork tapeworm Taenia solium may affect the human brain causing neurocysticercosis (NCC), a very frequent cause of neurological symptoms in developing countries. The clinical expression and response to treatment of human NCC are related to the location of cysticerci inside (intraparenchymal) or outside the brain parenchyma (extraparenchymal NCC). We used a naturally infected pig model to assess the characteristics of inflammation around brain cysticerci of parenchymal, meningeal and mixed locations. There were no major differences in inflammation without treatment. After antiparasitic treatment with praziquantel, inflammation around parenchymal brain cysticerci increased in comparison to meningeal located cysticerci. Cysticerci partially surrounded by both brain parenchyma and meninges showed increased inflammation in relation to the extent of the cysticercus in the brain parenchyma. The location of cysticerci within the brain is a factor that determines the extent and degree of the immune response following anticysticidal treatment. Similar changes may occur in treated human infections. Our work could contribute to explain the differences in response to antiparasitic treatment in different forms of human neurocysticercosis.

Infarction Distribution Pattern in Acute Stroke May Predict the Extent of Leptomeningeal Collaterals

Objective

The aim of this study was to evaluate whether the distribution pattern of early ischemic changes in the initial MRI allows a practical method for estimating leptomeningeal collateralization in acute ischemic stroke (AIS).

Methods

Seventy-four patients with AIS underwent MRI followed by conventional angiogram and mechanical thrombectomy. Diffusion restriction in Diffusion weighted imaging (DWI) and correlated T2-hyperintensity of the infarct were retrospectively analyzed and subdivided in accordance with Alberta Stroke Program Early CT score (ASPECTS). Patients were angiographically graded in collateralization groups according to the method of Higashida, and dichotomized in 2 groups: 29 subjects with collateralization grade 3 or 4 (well-collateralized group) and 45 subjects with grade 1 or 2 (poorly-collateralized group). Individual ASPECTS areas were compared among the groups.

Results

Means for overall DWI-ASPECTS were 6.34 vs. 4.51 (well vs. poorly collateralized groups respectively), and for T2-ASPECTS 9.34 vs 8.96. A significant difference between groups was found for DWI-ASPECTS (p<0.001), but not for T2-ASPECTS (p = 0.088). Regarding the individual areas, only insula, M1-M4 and M6 showed significantly fewer infarctions in the well-collateralized group (p-values <0.001 to 0.015). 89% of patients in the well-collateralized group showed 0–2 infarctions in these six areas (44.8% with 0 infarctions), while 59.9% patients of the poor-collateralized group showed 3–6 infarctions.

Conclusion

Patients with poor leptomeningeal collateralization show more infarcts on the initial MRI, particularly in the ASPECTS areas M1 to M4, M6 and insula. Therefore DWI abnormalities in these areas may be a surrogate marker for poor leptomeningeal collaterals and may be useful for estimation of the collateral status in routine clinical evaluation.

Ivy Sign on Fluid-Attenuated Inversion Recovery Images in Moyamoya Disease: Correlation with Clinical Severity and Old Brain Lesions

PURPOSE

Leptomeningeal collateral, in moyamoya disease (MMD), appears as an ivy sign on fluid-attenuated inversion-recovery (FLAIR) images. There has been little investigation into the relationship between presentation of ivy signs and old brain lesions. We aimed to evaluate clinical significance of ivy signs and whether they correlate with old brain lesions and the severity of clinical symptoms in patients with MMD.

MATERIALS AND METHODS

FLAIR images of 83 patients were reviewed. Each cerebral hemisphere was divided into 4 regions and each region was scored based on the prominence of the ivy sign. Total ivy score (TIS) was defined as the sum of the scores from the eight regions and dominant hemispheric ivy sign (DHI) was determined by comparing the ivy scores from each hemisphere. According to the degree of ischemic symptoms, patients were classified into four subgroups: 1) nonspecific symptoms without motor weakness, 2) single transient ischemic attack (TIA), 3) recurrent TIA, or 4) complete stroke.

RESULTS

TIS was significantly different as follows: 4.86±2.55 in patients with nonspecific symptoms, 5.89±3.10 in patients with single TIA, 9.60±3.98 in patients with recurrent TIA and 8.37±3.39 in patients with complete stroke (p=0.003). TIS associated with old lesions was significantly higher than those not associated with old lesions (9.35±4.22 vs. 7.49±3.37, p=0.032). We found a significant correlation between DHI and motor symptoms (p=0.001).

CONCLUSION

Because TIS has a strong tendency with severity of ischemic motor symptom and the presence of old lesions, the ivy sign may be useful in predicting severity of disease progression.

Induction of endogenous Type I interferon within the central nervous system plays a protective role in experimental autoimmune encephalomyelitis

The Type I interferons (IFN), beta (IFN-β) and the alpha family (IFN-α), act through a common receptor and have anti-inflammatory effects. IFN-β is used to treat multiple sclerosis (MS) and is effective against experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Mice with EAE show elevated levels of Type I IFNs in the central nervous system (CNS), suggesting a role for endogenous Type I IFN during inflammation. However, the therapeutic benefit of Type I IFN produced in the CNS remains to be established. The aim of this study was to examine whether experimentally induced CNS-endogenous Type I IFN influences EAE. Using IFN-β reporter mice, we showed that direct administration of polyinosinic–polycytidylic acid (poly I:C), a potent inducer of IFN-β, into the cerebrospinal fluid induced increased leukocyte numbers and transient upregulation of IFN-β in CD45/CD11b-positive cells located in the meninges and choroid plexus, as well as enhanced IFN-β expression by parenchymal microglial cells. Intrathecal injection of poly I:C to mice showing first symptoms of EAE substantially increased the normal disease-associated expression of IFN-α, IFN-β, interferon regulatory factor-7 and IL-10 in CNS, and disease worsening was prevented for as long as IFN-α/β was expressed. In contrast, there was no therapeutic effect on EAE in poly I:C-treated IFN receptor-deficient mice. IFN-dependent microglial and astrocyte response included production of the chemokine CXCL10. These results show that Type I IFN induced within the CNS can play a protective role in EAE and highlight the role of endogenous type I IFN in mediating neuroprotection.

[Meningioangiomatosis: a clinicopathological study of five cases]

OBJECTIVE

To investigate the clinicopathologic characteristics of meningioangiomatosis (MA).

METHODS

Five cases of MA were evaluated morphologically by HE and immunohistochemistry on formalin-fixed paraffin-embedded tissue. Clinical information was also obtained. The literature was reviewed. The clinical pathology and biological behavior of MA were discussed.

RESULTS

Five cases of MA were reported, arising in three males and two females, with an age range of 16 to 26 years at diagnosis. All five subjects had intractable seizure disorders, and the duration of illness ranged from 8 months to 18 years. The lesions were resected from the frontal lobe in four patients, and from the temporal lobe in one. All the lesions were confined to the cortex, firm in consistency, without capsules and had poor blood supply. There was focal involvement of the overlying leptomeninges. Microscopically, they showed characteristic features of MA, such as proliferating microvessels with perivascular cuffs of spindle-cell within the cortex. Some had numerous calcifications, others showed acidophilic granular bodies. The cells were positive for EMA and vimentin by immunohistochemistry, and for reticulin by histochemical staining.

CONCLUSIONS

MA is a rare, benign hamartomatous lesion of the central nervous system. It usually presents as plaque-like or nodular mass in the cerebral cortex and the overlying leptomeninges, consisting of meningovascular proliferation and leptomeningeal calcification. In some cases the lesion may show perivascular proliferation of elongated spindle-shaped cells. MA usually affects children and young adults, and is located in the frontal or temporal lobes with variable involvement of the overlying leptomeninges. Clinically, most of sporadic cases have a long history of intractable seizures despite multiantiepileptic drugs. MA has also been reported to coexist with arteriovenous malformations,meningiomas and other tumorous lesions.