Impact of aging on meningeal gene expression

BACKGROUND

The three-layered meninges cover and protect the central nervous system and form the interface between cerebrospinal fluid and the brain. They are host to a lymphatic system essential for maintaining fluid dynamics inside the cerebrospinal fluid-filled subarachnoid space and across the brain parenchyma via their connection to glymphatic structures. Meningeal fibroblasts lining and traversing the subarachnoid space have direct impact on the composition of the cerebrospinal fluid through endocytotic uptake as well as extensive protein secretion. In addition, the meninges are an active site for immunological processes and act as gatekeeper for immune cells entering the brain. During aging in mice, lymphatic drainage from the brain is less efficient contributing to neurodegenerative processes. Aging also affects the immunological status of the meninges, with increasing numbers of T cells, changing B cell make-up, and altered macrophage complement.

METHODS

We employed RNASeq to measure gene expression and to identify differentially expressed genes in meninges isolated from young and aged mice. Using Ingenuity pathway, GO term, and MeSH analyses, we identified regulatory pathways and cellular functions in meninges affected by aging.

RESULTS

Aging had profound impact on meningeal gene expression. Pathways related to innate as well as adaptive immunity were affected. We found evidence for increasing numbers of T and B lymphocytes and altered activity profiles for macrophages and other myeloid cells. Furthermore, expression of pro-inflammatory cytokine and chemokine genes increased with aging. Similarly, the complement system seemed to be more active in meninges of aged mice. Altered expression of solute carrier genes pointed to age-dependent changes in cerebrospinal fluid composition. In addition, gene expression for secreted proteins showed age-dependent changes, in particular, genes related to extracellular matrix composition and organization were affected.

CONCLUSIONS

Aging has profound effects on meningeal gene expression; thereby affecting the multifaceted functions meninges perform to maintain the homeostasis of the central nervous system. Thus, age-dependent neurodegenerative processes and cognitive decline are potentially in part driven by altered meningeal function.

Unvalidated Cerebrospinal Fluid Pressure Equations Should not Be Used for Research

This is a Letter to the Editor and does not have an abstract. Please download the PDF or view the article HTML.

Elevated perioptic lipocalin-type prostaglandin D synthase concentration in patients with idiopathic intracranial hypertension

The pathophysiology of vision loss and loss of visual field in patients with idiopathic intracranial hypertension with papilloedema is not fully understood. Although elevated CSF pressure induces damage to the optic nerve due to stasis of axoplasmic flow, there is no clear relationship between the severity of papilloedema and CSF pressure. Furthermore, there are cases of purely unilateral papilloedema and cases without papilloedema despite significantly elevated intracranial pressure as well as papilloedema that can persist despite a successfully lowered intracranial pressure. We hypothesize that at least in some of such cases, in addition to purely pressure-induced damage to the optic nerve, the biochemical composition of the CSF in the subarachnoid space surrounding the orbital optic nerve may play a role in the pathogenesis of vision loss. In this retrospective study, we report on lipocalin-type prostaglandin D synthase concentrations in the CSF within the perioptic and lumbar subarachnoid space in 14 patients with idiopathic intracranial hypertension (13 females, mean age 45 ± 13 years) with chronic persistent papilloedema resistant to maximum-tolerated medical therapy and visual impairment. CSF was collected from the subarachnoid space of the optic nerve during optic nerve sheath fenestration and from the lumbar subarachnoid space at the time of lumbar puncture. CSF was analysed for lipocalin-type prostaglandin D synthase and the concentrations compared between the two sites using nephelometry. The mean lipocalin-type prostaglandin D synthase concentration in the perioptic subarachnoid space was significantly higher compared with the concentration in the lumbar subarachnoid space (69 ± 51 mg/l without correction of serum contamination and 89 ± 67 mg/l after correction of serum contamination versus 23 ± 8 mg/l; P < 0.0001, Mann–Whitney U-test). These measurements demonstrate a change and imbalance in the biochemical environment of the optic nerve. Its possible effect is discussed.

Lipocalin-type Prostaglandin D Synthase Concentration Gradients in the Cerebrospinal Fluid in Normal-tension Glaucoma Patients with Optic Nerve Sheath Compartmentation

Objective

To report on the lipocalin-type prostaglandin D synthase (L-PGDS) concentrations in the cerebrospinal fluid (CSF) of the perioptic and lumbar subarachnoid space (SAS) in patients with radiologically proven optic nerve (ON) sheath compartmentation presenting as normal-tension glaucoma (NTG).

Methods

Retrospective biochemical analysis of CSF in thirteen patients with ON sheath compartmentation presenting as NTG (four females, mean age 70±8 years). CSF was sampled from the SAS of the ON during ON sheath fenestration for ON sheath compartmentation and from the lumbar SAS at the time of lumbar puncture. Nephelometry was used for the quantification of L-PGDS and albumin concentration. Albumin was measured in order to assess the amount of contamination with serum in the CSF samples taken from the ON SAS. Main outcome measures were L-PGDS concentrations in the CSF of the perioptic and lumbar SAS.

Results

Mean L-PGDS concentration was 24±8 mg/L in the lumbar SAS compared to 33±27 mg/L without correction of serum contamination and 45±39 mg/L after correction of serum contamination in the perioptic SAS. The difference between the lumbar and the perioptic SAS was statistically significant (P=0.0047 without correction of serum contamination, P=0.0002 with correction of serum contamination; Mann-Witney U-test).

Conclusion

This study demonstrates a concentration gradient of L-PGDS levels within the CSF with a statistically significant higher concentration in the compartmentalized perioptic SAS compared to that in the lumbar SAS. Biochemical changes in the perioptic SAS might be involved in the pathophysiology in NTG patients with ON sheath compartmentation.

Carotid-cavernous sinus fistula following mechanical thrombectomy in acute ischaemic stroke: a rare complication

Carotid-cavernous sinus fistulas (CCFs) are abnormal communications between the internal carotid artery (ICA) and the cavernous sinus (CS). Direct CCFs are associated with trauma or are iatrogenic complications of neuroendovascular procedures. Meanwhile, mechanical endovascular thrombectomy (MT) in acute ischaemic stroke (AIS) patients with large vessel occlusion (LVO) has been established as a common treatment approach. However, MT is not without its risks of complications, and only a few reports exist on CCF occurring after MT. Here, we present a case of a 63-year-old patient with iatrogenic high-flow CCF of the right horizontal cavernous ICA segment (C4) following repeated MT due to LVO of the middle cerebral artery, and the recent literature is reviewed.

Brain activation patterns in medicated versus medication-naïve adults with attention-deficit hyperactivity disorder during fMRI tasks of motor inhibition and cognitive switching

Background

Adult-attention-deficit-hyperactive-disorder (ADHD) is often unrecognized condition. FMRI examination along with neuropsychological testing might strengthen the diagnosis. We hypothesized that ADHD-adults with and without medication would show different fMRI pattern compared to healthy controls while testing tasks of motor inhibition and cognitive switching.

Methods

45 subjects in three age-matched groups: (1) controls, (2) ADHD-adults under medication (ADHD+) and (3) medication-naïve adults with ADHD (ADHD−) underwent fMRI and neuropsychological testing. Group analysis and population-based statistics were performed.

Results

DTVP-A, intellectual ability as well as attention capability, visual-perceptual and visual-motor abilities showed no significant differences between the groups. However, fMRI revealed statistically significant differences between the ADHD+, ADHD− and control groups on tasks of motor inhibition and cognitive switching on adults in bilateral fronto-striatal brain regions, inferior fronto-frontal, fronto-cingulate and fronto-parietal networks as well as in the parietal lobe (p < 0.05).

Conclusions

fMRI offers the potential to differentiate between the ADHD+, ADHD− and control groups. FMRI possibly opens a new window for monitoring the therapeutic effect of ADHD medication.

Trial registration

NCT02578342, registered at August 2015 to clinical trial registry (https://ichgcp.net/clinical-trials-registry/NCT02578342).

Clearance of neurotoxic peptides and proteins by meningothelial cells

Meningothelial cells (MECs) are the cellular component of the meninges that provide physical protection to the central nervous system (CNS). Their main function is the formation of a barrier enclosing the brain including the cerebrospinal fluid (CSF). Further, MECs are involved in maintaining CSF homeostasis by clearing CSF from bacteria and apoptotic cells. Furthermore, secretion of pro- and anti-inflammatory cytokines and chemokines involves MECs in immunological processes in the CNS. We demonstrated that meningothelial Ben-Men-1 cells ingest neurotoxic peptides amyloid-β (Aβ^1-40) and protein α-synuclein up to about 10-fold more efficiently compared to neuronal-like SH-SY5Y cells. Aβ^1-40 and α-synuclein are mainly taken up via macropinocytosis. Caveolar endocytosis in addition contributes to α-synuclein ingestion. Upon uptake, both are trafficked towards lysosomal degradation. While production of reactive oxygen species (ROS) following exposure to Aβ^25-35 and α-synuclein was similar between Ben-Men-1 and SH-SY5Y cells, mitochondrial function in Ben-Men-1 was significantly more robust to Aβ^25-35 treatment compared to neuronal-like SHSY5Y cells. Similarly, Ben-Men-1 were significantly less susceptible to Aβ^25-35-induced cell death than neuronal-like cells. Furthermore, co-culture with Ben-Men-1 offered significant protection to neuronal-like cells against Aβ^25-35-induced apoptosis. This study reveals for the first time the function of MECs as scavengers of neurotoxic Aβ and α-synuclein, thereby connecting these cells to neuroprotective processes and suggesting a new mechanism and pathway for clearing neurotoxic substances from the CSF.

The extracellular matrix composition of the optic nerve subarachnoid space

The meninges not only surround the brain and the spinal cord but also the optic nerve. Meningeal-derived extracellular matrix (ECM) is a crucial component of the pial basement membrane, glia limitans and important for maintenance of optic nerve axon integrity, homeostasis and retinal ganglion cell health. To get closer insight into optic nerve meningeal-derived ECM composition, we performed proteomic analysis of the sheep optic nerve subarachnoid space (SAS). Candidate components were confirmed in cultures of primary human meningothelial cells (phMECs) and human optic nerve samples. Sheep optic nerve SAS samples were analysed by LC-MS, identified proteins were matched to their human orthologs and filtered using gene lists representing all major ECM components. To validate these findings digital droplet PCR (ddPCR) to evaluate mRNA expression of all candidate components identified was performed on cultures of phMECs. In addition, one protein per major ECM group was stained on human optic nerve sections and on phMEC cultures. Employing LC-MS, 1273 proteins were identified and subjected to bioinformatic analysis. Gene ontology analysis revealed six out of forty-four collagen types (1A1, 1A2, 3A1, 6A2, 6A3 and 14A1), three out of eleven laminin subunits (A4, B2, C1) and six out of twenty-seven hyaluronan binding proteins (CD44, versican (VCAN), C1q binding protein, neurocan (NCAN), brevican (BCAN) and hyalaluronan proteoglycan link protein 2 (HAPLN2)) were present in our cohort. DdPCR in phMEC cell culture confirmed presence of all candidate components except NCAN, BCAN and HAPLN2. Immunohistochemistry (IHC) staining on human optic nerve sections and immunofluorescence (IF) staining on in vitro cultured phMECs showed strong immunopositivity for collagen-typeI-α1 (COL1A1), lamininγ1 (LAMC1), and VCAN. Fibronectin (FN1) was exclusively present in cultures of phMECs. Using a combined bioinformatics and immunohistological approach, we describe the ECM composition of the optic nerve subarachnoid space. As this space plays an important role in maintaining optic nerve function, a better understanding of ECM composition in this delicate environment might be key to further pathophysiological insight into optic nerve degeneration and associated disorders.

Persistent Globe Flattening in Astronauts following Long-Duration Spaceflight

Posterior globe flattening has been well-documented in astronauts both during and after long-duration space flight (LDSF) and has been observed as early as 10 days into a mission on the International Space Station. Globe flattening (GF) is thought to be caused by the disc centred anterior forces created by elevated volume and/or pressure within the optic nerve sheath (ONS). This might be the result of increased intracranial pressure, increased intraorbital ONS pressure from compartmentalisation or a combination of these mechanisms. We report posterior GF in three astronauts that has persisted for 7 years or more following their return from LDSFs suggesting that permanent scleral remodelling may have occurred.

A perfusion bioreactor-based 3D model of the subarachnoid space based on a meningeal tissue construct

BACKGROUND

Altered flow of cerebrospinal fluid (CSF) within the subarachnoid space (SAS) is connected to brain, but also optic nerve degenerative diseases. To overcome the lack of suitable in vitro models that faithfully recapitulate the intricate three-dimensional architecture, complex cellular interactions, and fluid dynamics within the SAS, we have developed a perfusion bioreactor-based 3D in vitro model using primary human meningothelial cells (MECs) to generate meningeal tissue constructs. We ultimately employed this model to evaluate the impact of impaired CSF flow as evidenced during optic nerve compartment syndrome on the transcriptomic landscape of MECs.

METHODS

Primary human meningothelial cells (phMECs) were seeded and cultured on collagen scaffolds in a perfusion bioreactor to generate engineered meningeal tissue constructs. Engineered constructs were compared to human SAS and assessed for specific cell-cell interaction markers as well as for extracellular matrix proteins found in human meninges. Using the established model, meningeal tissue constructs were exposed to physiological and pathophysiological flow conditions simulating the impaired CSF flow associated with optic nerve compartment syndrome and RNA sequencing was performed.

RESULTS

Engineered constructs displayed similar microarchitecture compared to human SAS with regards to pore size, geometry as well as interconnectivity. They stained positively for specific cell-cell interaction markers indicative of a functional meningeal tissue, as well as extracellular matrix proteins found in human meninges. Analysis by RNA sequencing revealed altered expression of genes associated with extracellular matrix remodeling, endo-lysosomal processing, and mitochondrial energy metabolism under pathophysiological flow conditions.

CONCLUSIONS

Alterations of these biological processes may not only interfere with critical MEC functions impacting CSF and hence optic nerve homeostasis, but may likely alter SAS structure, thereby further impeding cerebrospinal fluid flow. Future studies based on the established 3D model will lead to new insights into the role of MECs in the pathogenesis of optic nerve but also brain degenerative diseases.

Impaired cerebrospinal fluid dynamics along the entire optic nerve in normal-tension glaucoma

PURPOSE

To investigate the cerebrospinal fluid (CSF) dynamics along the entire optic nerve (ON) in patients with normal-tension glaucoma (NTG).

METHODS

Retrospective analysis of computed tomographic (CT) cisternographies in Caucasian patients with NTG. Fifty-six patients (99 of 112 eyes) fulfilled the diagnostic criteria of NTG and underwent CT-cisternography. Twelve subjects without NTG (24 eyes) served as controls. Contrast-loaded cerebrospinal fluid (CLCSF) density measurements in Hounsfield units (HU) were performed at four defined regions along the ON and in the basal cistern.

RESULTS

In NTG patients, the mean density CLCSF in the bulbar segment measured 76 ± 49 HU right and 88 ± 74 HU left, in the mid-orbital segment 117 ± 92 HU right and 119 ± 73 HU left, in the intracanalicular ON portion 209 ± 88 HU right and 216 ± 101 HU left, in the intracranial ON portion 290 ± 106 HU right and 286 ± 118 HU left and in the basal cistern 517 ± 213 HU. The distribution of CLCSF along the ON showed a statistically significant reduction in the intraorbital ON segments in NTG patients compared to controls without NTG with the far largest difference within the retrobulbar segment (-150 HU right and -117 HU left; right: p < 0.001, left: p < 0.001).

CONCLUSION

This study demonstrates a gradual reduction in CLCSF towards the retrobulbar segment in NTG, while in controls without NTG, no reduction in CLCSF was measured within the orbital segments. Impaired CSF dynamics along the ON may contribute to the pathophysiology of NTG.

Perioptic Cerebrospinal Fluid Dynamics in Idiopathic Intracranial Hypertension

Purpose: To examine the cerebrospinal fluid (CSF) dynamics along the entire optic nerve in patients with idiopathic intracranial hypertension (IIH) and papilledema by computed tomographic (CT) cisternography. Methods: Retrospective analysis of CT cisternographies in 16 patients with a history of IIH and papilledema (14 females and 2 males, mean age: 49 ± 16 years). Contrast loaded CSF (CLCSF) was measured in Hounsfield Units (HU) at three defined regions of interest (ROI) along the optic nerve (orbital optic nerve portion: bulbar and mid-orbital segment, intracranial optic nerve portion) and additionally in the basal cistern. The density measurements in ROI 1, ROI 2, and ROI 3 consist of measurements of the optic nerve complex: optic nerve sheath, CLCSF filled SAS and optic nerve tissue. As controls served a group of patients (mean age: 60 ± 19 years) without elevated intracranial pressure and without papilledema. Results: In IIH patients the mean CLCSF density in the bulbar segment measured 65 ± 53 HU on the right and 63 ± 35 HU on the left side, in the mid-orbital segment 68 ± 37 HU right and 60 ± 21 HU left. In the intracranial optic nerve portion 303 ± 137 HU right and 323 ± 169 HU left and in the basal cistern 623 ± 188 HU. Within the optic nerve the difference of CLCSF density showed a highly statistical difference (p < 0.001) between the intracranial optic nerve portion and the mid-orbital segment. CLCSF density was statistically significantly (p < 0.001) reduced in both intraorbital optic nerve segments in patients with IIH compared to controls. Conclusions: The current study demonstrates reduced CLCSF density within the orbital optic nerve segments in patients with IIH and papilledema compared to 12 controls without elevated intracranial pressure and without papilledema. Impaired CSF dynamics could be involved in the pathophysiology of optic nerve damage in PE in IIH.

Normal tension glaucoma: review of current understanding and mechanisms of the pathogenesis

Normal tension glaucoma (NTG) is an exception in the "glaucoma family" where the major risk factor, increased intraocular pressure, is missing. If not increased intraocular pressure, then what other causes can then lead to glaucomatous optic disc change and visual field loss in NTG? Several possibilities will be discussed. Among them a higher sensitivity to normal pressure, vascular dysregulation, an abnormally high translaminar pressure gradient and a neurodegenerative process due to impaired cerebrospinal fluid dynamics in the optic nerve sheath compartment. There are many excellent review papers published on normal tension glaucoma (NTG). The aim of this paper is therefore not to add another extensive review on NTG but rather to focus on and to discuss some possible mechanisms that are thought to be involved in the pathophysiology of NTG and to discuss the stronger and weaker aspects of each concept. The fact that several concepts exist suggests that NTG is still not very well understood and that no single mechanism on its own might adequately explain NTG.

Optic Nerve Compartment Syndrome in a Patient with Optic Nerve Sheath Meningioma

PURPOSE

To report a patient with optic nerve (ON) sheath meningioma, unilateral optic disc swelling, and inhomogeneous cerebrospinal fluid (CSF) composition between lumbar CSF and CSF from the subarachnoid space (SAS) of the affected ON.

METHODS

A 39-year-old woman presented with unilateral optic disc swelling and slight deterioration of visual function in the left eye. Extensive laboratory workup and magnetic resonance imaging (MRI) of the brain and orbits were performed. As radiotherapy was refused by the patient, ON sheath fenestration (ONSF) was offered and performed in order to stop deterioration. CSF from the SAS of the ON was sampled.

RESULTS

Laboratory workup was within normal limits. MRI of the left orbit demonstrated enhancement of the dura in the precanalicular portion of the ON and distension of the SAS, most prominent in the bulbar portion of the ON. On lumbar puncture the opening pressure measured 19 (cm H2O). Compared to the lumbar CSF the CSF of the affected ON SAS showed markedly elevated measurements for albumin, IgG, and beta-trace protein. Visual function remained stable over a follow-up time of 18 months.

CONCLUSIONS

Composition of CSF is considered to be homogenous throughout all CSF spaces. In this patient the authors found a marked concentration-gradient of albumin, IgG, and beta-trace protein between the CSF in the spinal canal and the CSF in the SAS of the affected ON. Based on the radiologic features of the left ON and the dissociated beta-trace protein concentrations in the CSF of the SAS of the ON and the lumbar CSF, the diagnosis of an ON sheath compartment syndrome due to an ON sheath meningioma was made.

When is Isolated Inferior Oblique Muscle Surgery an Appropriate Treatment for Superior Oblique Palsy?

Purpose

To evaluate the efficacy of isolated inferior oblique muscle weakening in the treatment of superior oblique palsy.

Methods

Forty-seven patients with superior oblique palsy underwent either single-muscle surgery (anteriorization or recession of the inferior oblique muscle) or two-muscle surgery (anteriorization of the inferior oblique muscle combined with recession of the contralateral inferior rectus muscle according to the amount of vertical deviation). In a retrospective non-comparative study the objective surgical effect was calculated as the difference between the deviation at the day before surgery and the deviations 6 weeks and at least 1 year after surgery. Pre- and postoperative sensorimotor status and subjective outcome were evaluated.

Results

In patients who underwent isolated inferior oblique muscle surgery the mean preoperative vertical deviation decreased from 15±9 (distance)/16±10 (near) prism diopters (PD) (anteriorization) and 7±5 (distance)/9±8 (near) PD (recession) to 4±4 (distance)/4±6 (near) PD (anteriorization) and 2±2 (distance)/2±3 (near) PD (recession) at the 1-year follow-up. In patients who underwent two-muscle surgery the mean vertical deviation decreased from 20±11 (distance)/21±10 (near) PD preoperatively and 6±7 (distance)/6±6 (near) PD at 1-year follow-up. Subjective assessment showed excellent scores among the patients treated with single-muscle surgery and slightly lower but also favorable scores among the patients treated with combined techniques. A direct comparison of the different outcome scores was not possible because of the more difficult initial situation in patients who underwent combined surgery.

Conclusions

Isolated inferior oblique muscle weakening is an effective treatment option for superior oblique palsy up to 15 PD of vertical deviation in primary position. Two-muscle surgery should be reserved for patients with larger vertical deviations.

Clinically Directed Neuroimaging of Ophthalmoplegia

PURPOSE

Ophthalmoplegia (OP) can have numerous etiologies and different clinical presentations. Most causes of OP can be narrowed down to specific anatomical locations based on clinical information. The aim of this study was to outline the different categories of diseases encountered in patients with OP, based on the location along the ocular motor pathways, and the most appropriate imaging modality for the given scenarios.

METHODS

Representative neuroimaging examples of pathological processes causing OP are displayed, sequenced by anatomical location and disease category. Correlations between the clinical presentation and site of pathology with imaging protocol recommendations are also presented.

RESULTS

Diseases affecting ocular movement can be divided into categories including: injuries or diseases of the cerebral hemispheres, midbrain, pons, and cerebellum, ocular motor nerve palsies, intrinsic extraocular muscle diseases and orbital diseases secondarily affecting the extraocular muscles. The cranial nerves responsible for ocular movements can be affected intrinsically or extrinsically along their nuclei, their course in the brainstem, in the cisterns, skull base, cavernous sinuses and orbits. The extraocular muscles can be affected primarily or secondarily by adjacent pathological processes in the orbit. Clinical information can help narrow down the differential diagnoses in terms of anatomical site of involvement and prompt the most appropriate neuroimaging techniques.

CONCLUSION

By understanding the pathophysiology of OP the neuroradiologist can discuss clinical cases with the referring clinician and determine a timely, accurate method of imaging to achieve the most precise differential diagnosis.

Translaminar pressure in Caucasian normal tension glaucoma patients

PURPOSE

The aim of this study was to examine the translaminar pressure difference (TLP) in Caucasian patients with normal tension glaucoma (NTG) and its possible impact onto the pathogenesis of NTG.

METHODS

Retrospective analysis of medical records of patients with open-angle glaucoma (OAG) in the period from 2005 to 2015 from the Ophthalmology Department, Cantonal Hospital Aarau, Switzerland. A total of 67 eyes of 38 patients (mean age 68.6 ± 11.3 years, 21 women and 17 men) fulfilled the diagnostic criteria of progressive NTG and underwent lumbar puncture (LP) during computer-assisted cisternography (CT - cisternography). The intraocular pressure (IOP) and lumbar cerebrospinal fluid pressure (CSF-p) were analysed and the TLP calculated. The TLP was compared with the mean defect (MD) of visual fields. Statistical analysis was performed with the one and two-tailed paired and unpaired t-test and the non-parametric Spearman correlation test.

RESULTS

The mean lumbar opening CSF-p measured 11.6 ± 3.7 mmHg. The mean IOP in the right eye measured 14.7 ± 2.4 mmHg, in the left eye 14.7 ± 2.5 mmHg. The calculated mean TLP was 3.0 ± 4.2 mmHg in the right and 3.3 ± 4.3 mmHg in the left eye. There was no significant correlation between TLP and the MD of visual fields in both eyes.

CONCLUSIONS

This study did not confirm either a lower lumbar CSF-p or increased TLP compared to previous retrospective and prospective studies. As cerebrospinal fluid (CSF) flow is not homogenous throughout all CSF spaces and CSF-p and IOP fluctuate, the current view on TLP needs modifications to improve its validity.

Cell-Cell Interaction Proteins (Gap Junctions, Tight Junctions, and Desmosomes) and Water Transporter Aquaporin 4 in Meningothelial Cells of the Human Optic Nerve

Purpose

Meningothelial cells (MECs) play a central role in the maintenance of cerebrospinal fluid (CSF) homeostasis and in physiological and pathophysiological processes within the subarachnoid space (SAS) linking them to optic nerve (ON) pathologies. Still, not much is known about their structural properties that might enable MECs to perform specific functions within the ON microenvironment.

Methods

For closer characterization of the structural properties of the human MEC layer in the arachnoid, we performed immunohistological analyses to evaluate the presence of cell–cell interaction markers, namely, markers for tight junctions (JAM1, Occludin, and Claudin 5), gap junctions (Connexin 26 and 43), and desmosomes (Desmoplakin) as well as for water channel marker aquaporin 4 (AQP4) in retrobulbar, midorbital, and intracanalicular human ON sections.

Results

MECs displayed immunopositivity for markers of tight junctions (JAM1, Occludin, and Claudin 5) and gap junctions (Connexin 26 and 43) as well as for AQP4 water channels. However, no immunopositivity was found for Desmoplakin.

Conclusion

MECs are connected via tight junctions and gap junctions, and they possess AQP4 water channels. The presence of these proteins emphasizes the important function of MECs within the ON microenvironment as part of the meningeal barrier. Beyond this barrier function, the expression of these proteins by MECs supports a broader role of these cells in signal transduction and CSF clearance pathways within the ON microenvironment.

Relationship between the optic nerve sheath diameter and lumbar cerebrospinal fluid pressure in patients with normal tension glaucoma

PurposeTo investigate on the relationship between the optic nerve sheath diameter (ONSD) and the lumbar cerebrospinal fluid pressure (CSF-p) in Caucasian patients with normal tension glaucoma (NTG).Patients and methodsRetrospective analysis of medical records of patients with open-angle glaucoma in the period from 2005 to 2015 from the Ophthalmology Department, Cantonal Hospital Aarau, Switzerland was performed. A total of 38 patients (mean age 68.6±11.3 years, 21 females and 17 males) fulfilled the diagnostic criteria of NTG and underwent computed tomography (CT) of the orbit and lumbar puncture (LP). In total, 38 age- and gender-matched Caucasian subjects (mean age: 68.9±10.9 years) without known ON diseases served as controls for ONSD measurements. ONSDs were measured at a distance of 3 mm from the posterior globe and lumbar CSF-p was related to the measurements. Statistical analysis was performed by using the independent two-tailed t-test and the non-parametric Spearman's correlation test.ResultsThe mean ONSD in NTGs measured 6.4±0.9 mm and in controls 5.4±0.6 mm. The difference between NTGs and controls showed statistical significance (t-test: P<0.000). The mean CSF-p in NTG was 11.6±3.7 mm Hg. There was no statistical significant correlation between ONSD and CSF-p (Spearman's correlation coefficient ρ=0.06, P=0.72).ConclusionsThis study demonstrates enlarged ONSDs and normal lumbar CSF-p in 38 Caucasian NTG patients. As enlarged ONSDs generally are associated with increased intracranial CSF-p, these results can be explained by a disturbed communication of CSF-p between the intracranial and intraorbital subarachnoid spaces.

The Optic Canal: A Bottleneck for Cerebrospinal Fluid Dynamics in Normal-Tension Glaucoma?

Purpose

To report on the optic canal cross-sectional area (OCA) in Caucasian patients with normal-tension glaucoma (NTG) compared with Caucasian control subjects without known optic nerve (ON) diseases.

Methods

Retrospective analysis of computed tomographic images of the cranium and orbits in 56 NTG patients (30 females and 26 males; 99 of 112 eyes; mean age 67.7 ± 11.1 years). Fifty-six age- and gender-matched subjects (mean age: 68.0 ± 11.2 years) without known ON diseases served as controls. The OCA at the orbital opening was measured in square millimeters by using the tool “freehand.” Statistical analysis was performed by using the independent two-tailed t-test.

Results

The mean orbital opening OCA in NTGs measured 14.5 ± 3.5 mm² (right OCA: 14.4 ± 3.6 mm², left OCA: 14.5 ± 3.4 mm²) and in controls measured 18.3 ± 2.6 mm² (right OCA: 18.5 ± 2.7 mm², left OCA: 18.1 ± 2.5 mm²). The difference between NTG and controls was statistically significant (p < 0.000 for the right OCA, p < 0.000 for the left OCA).

Conclusion

This study demonstrates narrower OCAs in Caucasian NTG patients compared with Caucasian control subjects without known ON diseases. Narrower OCAs might contribute to a discontinuity of the cerebrospinal fluid flow between the intracranial and orbital subarachnoid space in NTG patients. This might have an influence onto the pathophysiology in NTG.

Anti-inflammatory response following uptake of apoptotic bodies by meningothelial cells

BACKGROUND

Meningothelial cells (MECs) are the cellular components of the meninges. As such, they provide important barrier function for the central nervous system (CNS) building the interface between neuronal tissue and the cerebrospinal fluid (CSF), and are also part of the immune response of the CNS.

METHODS

Human, immortalized MECs were analyzed by flow cytometry and confocal microscopy to study the uptake of apoptotic cells. Furthermore, cytokine and chemokine production by MECs was analyzed by cytokine array and ELISA.

RESULTS

We found that MECs are highly active phagocytes able of ingesting and digesting large amounts of apoptotic cells. Furthermore, the uptake of apoptotic cells by MECs was immune suppressive via inhibiting the secretion of pro-inflammatory and chemoattractant cytokines and chemokines IL-6, IL-8, IL-16, MIF, and CXCL1, while increasing the secretion of anti-inflammatory IL-1 receptor antagonist by MECs.

CONCLUSION

MECs respond with the secretion of anti-inflammatory cytokines and chemokines following the uptake of apoptotic cells potentially connecting these cells to processes important for the shut-down of immune responses in the brain.

Meningothelial cells as part of the central nervous system host defence

BACKGROUND INFORMATION

Meningothelial cells (MECs) are the cellular components of the meninges protecting the brain and as such provide important barrier function for the central nervous system building the interface between neuronal tissue and the cerebrospinal fluid (CSF). MECs were previously shown to be involved in the clearance of waste products from the CSF and in maintaining the optic nerve microenvironment. In addition, MECs are involved in immunological processes in the brain by secretion of pro-inflammatory cytokines in response to various pathologically relevant stress conditions.

RESULTS

In this study, we analysed the uptake of latex beads as well as bacteria by human MECs using flow cytometric analyses. We found that MECs are highly active phagocytes able of ingesting large amounts of latex beads, as well as Gram-positive and Gram-negative bacteria. Phagocytic activity of MECs was sensitive to nocodazole and cytochalasin D treatment to a varying degree depending on particle composition. Interestingly, Gram-positive bacteria such as Staphylococcus aureus are more readily taken up compared with Gram-negative Escherichia coli. In addition, pre-treatment of MECs with lipopolysaccharide (LPS) or phorbol-12-myristate-13-acetate (PMA) enhanced S. aureus uptake, whereas PMA but not LPS was effective in enhancing E. coli uptake.

CONCLUSIONS

Thus, MECs are highly active facultative phagocytes likely important for the maintenance of CSF homeostasis and host defence in the central nervous system especially against Gram-positive bacteria.

Intraoperative magnetic resonance imaging and early prognosis for vision after transsphenoidal surgery for sellar lesions

Object

Sellar lesions with suprasellar extension may cause loss of visual acuity and visual field damage due to compression of the optic chiasm. Using intraoperative MR (iMR) imaging to detect symptomatic lesion remnants adjacent to the optic chiasm (that may be resected in the same procedure) may positively affect the functional outcome of patients with these lesions. The aim of this study was to evaluate the correlation between visual improvement and optic nerve decompression detected by iMR imaging in patients undergoing transsphenoidal resection of pituitary lesions.

Methods

A total of 32 patients (23 men and 9 women) who underwent transsphenoidal resection of sellar lesions causing visual impairment were included in this study. Tumor volume ranged from 0.9 cm3 to 55.7 cm3 (mean 9.8 ± 11.7 cm3). Preoperative assessment showed visual field damage in 31 patients (97%) and loss of visual acuity in 28 patients (88%). The latency period between the appearance of symptoms and transsphenoidal decompression was 14.9 ± 19.5 weeks.

Results

Intraoperative MR imaging was performed after the resection was believed to be complete, or if further tumor removal was not safely possible due to changed conditions in the surgical field. Complete resection was detected on these initial scans in 17 patients (53%). Partial resection was achieved in 9 patients (28%) and tumor debulking in 6 (19%). Additional resection was possible in 8 (53%) of these 15 patients. Four (50%) of these 8 cases had suprasellar remnants and the optic chiasm was subsequently decompressed. In 5 cases optimal decompression of the optic chiasm was not possible. On early follow-up within 1 month after surgery, overall improvement of visual field damage was observed in 27 patients (87%). In 23 patients (74%), the Goldmann perimetry demonstrated complete recovery. Improvement of visual acuity was noted in 24 patients (86%). Eighteen patients (64%) regained full visual acuity. Identification of a decompressed optic chiasm on iMR imaging was significantly correlated with visual field improvement (p = 0.0007; positive predictive value 0.96, 95% CI 0.81–0.99) and relief of visual acuity deficits (p = 0.0002; positive predictive value 0.96, 95% CI 0.79–0.99). Two patients needed transcranial procedures for symptomatic tumor remnants detected on iMR imaging.

Conclusions

Intraoperative MR imaging findings correlate with prognosis of visual deficits after transsphenoidal decompression of the anterior optic pathways. The use of iMR imaging may prevent revision surgery for unexpected symptomatic remnants.

Meningothelial cells react to elevated pressure and oxidative stress

BACKGROUND

Meningothelial cells (MECs) are the cellular components of the meninges enveloping the brain. Although MECs are not fully understood, several functions of these cells have been described. The presence of desmosomes and tight junctions between MECs hints towards a barrier function protecting the brain. In addition, MECs perform endocytosis and, by the secretion of cytokines, are involved in immunological processes in the brain. However, little is known about the influence of pathological conditions on MEC function; e.g., during diseases associated with elevated intracranial pressure, hypoxia or increased oxidative stress.

METHODS

We studied the effect of elevated pressure, hypoxia, and oxidative stress on immortalized human as well as primary porcine MECs. We used MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) bioreduction assays to assess the proliferation of MECs in response to treatment and compared to untreated control cells. To assess endocytotic activity, the uptake of fluorescently labeled latex beads was analyzed by fluorescence microscopy.

RESULTS

We found that exposure of MECs to elevated pressure caused significant cellular proliferation and a dramatic decrease in endocytotic activity. In addition, mild oxidative stress severely inhibited endocytosis.

CONCLUSION

Elevated pressure and oxidative stress impact MEC physiology and might therefore influence the microenvironment of the subarachnoid space and thus the cerebrospinal fluid within this compartment with potential negative impact on neuronal function.

Cerebrospinal fluid segregation optic neuropathy: an experimental model and a hypothesis

AIM

To describe the histological changes in the optic nerve (ON) after experimental segregation of cerebrospinal fluid (CSF).

METHODS

In seven sheep, a silicone band was placed around one ON to compress the subarachnoid space (SAS) surrounding the nerve, thus blocking the flow of CSF without compressing the ON itself. After 4 or 21 days, both the ligated and untouched ONs were removed and evaluated histologically.

RESULTS

All treated ONs showed marked loss of axons, destruction of myelin and swelling of meningoepithelial cells, most pronounced in the proximal ON adjacent to the globe at the location most distant to the ligature. There was no significant difference in histological findings between the ONs that were ligated for 4 days and those with 21 days of ligature.

CONCLUSION

CSF segregation in the ON by blocking the SAS leads within 4 days to severe nerve damage. The increasing severity of these changes with increasing distance from the site of the ligature argues against simple pressure- or microperfusion-dependent effects and supports the hypothesis that interruption of CSF flow in the SAS of the ON can produce damage due to a change of CSF flow and content.

Papilledema revisited: is its pathophysiology really understood?

The term 'papilledema' is used to describe swelling of the optic disc that is thought or known to be associated with increased intracranial pressure (ICP) transmitted to the subarachnoid space (SAS) surrounding the optic nerve (ON). In most cases, the diagnosis of increased ICP is confirmed by lumbar puncture, the results of which are believed to represent the pressure in all of the cerebrospinal fluid (CSF) spaces. Until recently, all CSF spaces were thought to communicate freely and that CSF pressure and composition in one location were the same throughout the central nervous system (CNS) unless there was an acquired structural disturbance. However, the concept of continuous CSF flow and pressure throughout the CNS does not explain why some patients with elevated ICP do not develop papilledema, why some patients have highly asymmetrical papilledema, or why some patients with papilledema have normal ICP during 24-hour monitoring. In addition, CSF sampling during lumbar puncture and during ON sheath fenestration demonstrates an increased concentration of lipocalin-like prostaglandin D synthase, a substance toxic to astrocytes, in the SAS of the ON compared with that in the lumbar CSF space, and also a difference in CSF dynamics between the lumbar and ON SAS in some patients with papilledema. We therefore suggest that papilledema does not result from raised ICP alone but in some cases by compartmentation of the SAS of the ON, leading to a toxic milieu around the nerve.

'Spontaneous' periocular hemorrhage and macrohematuria

PURPOSE

To report on a 19-year-old man with 'spontaneous' periocular hemorrhage and macrohematuria as the first signs of a bone-marrow-infiltrating rhabdomyosarcoma of the left superior rectus muscle.

PROCEDURES

Clinical eye examination, magnetic resonance imaging, laboratory workup and bone marrow biopsy were performed.

RESULTS

Magnetic resonance imaging showed a mass lesion in the left superior rectus muscle. While funduscopy had initially been normal, optic disc swelling, retinal hemorrhage and vitreous cell infiltration could be seen in the further course of disease. Laboratory work-up showed macrohematuria, thrombocytopenia and decreased concentration levels of plasma fibrinogen. Thromboplastin time was decreased. A bone marrow biopsy revealed small cell infiltration; using immunohistochemistry, a rhabdomyosarcoma was diagnosed. Unfortunately, the patient died few months later, in spite of chemotherapy.

CONCLUSION

'Spontaneous' periocular hemorrhage and macrohematuria were the first signs of a bone-marrow-infiltrating rhabdomyosarcoma in this young and otherwise healthy patient.

Does immunohistochemistry allow easy detection of lymphatics in the optic nerve sheath?

We evaluated the validity of anti-D2-40 and anti-LYVE-1 (antibodies against lymphatic endothelium) for IHC diagnosis and semiquantification of lymphatic vessels in the dura mater of the intraorbital portion of the human optic nerve (ON). Fourteen specimens were analyzed using light microscopy within 12 hr postmortem. We found in all specimens that both D2-40 and LYVE-1 stained lymphatic vessels as well as venules and arterioles. Our findings show lymphatic vessels in the meninges of the intraorbital portion of the human ON. Anti-D2-40 and anti-LYVE-1 antibodies, however, are not found to be exclusively specific to the endothelial layer of lymphatics because they also stain the endothelial layer of venules and arterioles. For the unequivocal identification of lymphatics, additional morphological criteria are necessary. Nevertheless, D2-40 and LYVE-1 staining allows rapid identification of endothelial layers.