Identification of lymphatic endothelium in cranial arachnoid granulation-like dural gap.

The dynamics of cerebrospinal fluid (CSF) are essential for maintaining homeostasis in the central nervous system. Despite insufficiently detailed descriptions of their structural and molecular properties for a century, cranial arachnoid granulations (CAGs) on meninges have been thought to participate in draining CSF from the subarachnoid space into the dural sinuses. However, recent studies have demonstrated the existence of other types of CSF drainage systems, such as lymphatic vessels adjacent to dural sinus and paravascular space in the brain so-called glymphatic system. Therefore, the role of CAGs in CSF drainage has become dubious. To better understand CAG function, we analyzed the ultrastructure and molecular identity of CAG-like structure on meninges adjacent to the superior sagittal sinus of pigs. Transmission electron microscopy analysis revealed that this structure has a reticular conglomerate consisting of endothelial cells that resembles lymphatic linings. Furthermore, immunohistochemistry and immunoelectron microscopy showed that they express molecules specific to lymphatic endothelial cell. We coined a name 'CAG-like dural gap (CAG-LDG)' to this structure and discussed the physiological relevance in terms of CSF drainage.

TRP Channels in the Focus of Trigeminal Nociceptor Sensitization Contributing to Primary Headaches.

Pain in trigeminal areas is driven by nociceptive trigeminal afferents. Transduction molecules, among them the nonspecific cation channels transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), which are activated by endogenous and exogenous ligands, are expressed by a significant population of trigeminal nociceptors innervating meningeal tissues. Many of these nociceptors also contain vasoactive neuropeptides such as calcitonin gene-related peptide (CGRP) and substance P. Release of neuropeptides and other functional properties are frequently examined using the cell bodies of trigeminal neurons as models of their sensory endings. Pathophysiological conditions cause phosphorylation, increased expression and trafficking of transient receptor potential (TRP) channels, neuropeptides and other mediators, which accelerate activation of nociceptive pathways. Since nociceptor activation may be a significant pathophysiological mechanism involved in both peripheral and central sensitization of the trigeminal nociceptive pathway, its contribution to the pathophysiology of primary headaches is more than likely. Metabolic disorders and medication-induced painful states are frequently associated with TRP receptor activation and may increase the risk for primary headaches.

Ultrastructural and Molecular Characterization of Platelet-derived growth factor Beta-Positive Leptomeningeal Cells in the Adult Rat Brain.

The leptomeninges, referring to the arachnoid and pia mater and their projections into the perivascular compartments in the central nervous system, actively participate in diverse biological processes including fluid homeostasis, immune cell infiltrations, and neurogenesis, yet their detailed cellular and molecular identities remain elusive. This study aimed to characterize platelet-derived growth factor beta (PDGFR-ß)-expressing cells in the leptomeninges in the adult rat brain using light and electron microscopy. PDGFR-ß+ cells were observed in the inner arachnoid, arachnoid trabeculae, pia mater, and leptomeningeal sheath of the subarachnoid vessels, thereby forming a cellular network throughout the leptomeninges. Leptomeningeal PDGFR-ß+ cells were commonly characterized by large euchromatic nuclei, thin branching processes forming web-like network, and the expression of the intermediate filaments nestin and vimentin. These cells were typical of active fibroblasts with a well-developed rough endoplasmic reticulum and close spatial correlation with collagen fibrils. Leptomeningeal PDGFR-ß+ cells ensheathing the vasculature in the subarachnoid space joined with pial PDGFR-ß+ cells upon entering the cortical parenchyma, yet perivascular PDGFR-ß+ cells in these penetrating vessels underwent abrupt changes in their morphological and molecular characteristics: they became more flattened with loss of immunoreactivity for nestin and vimentin and deficient collagen deposition, which was indicative of inactive fibroblasts termed fibrocytes. In the cortical parenchyma, PDGFR-ß immunoreactivity was almost exclusively localized to larger caliber vessels, and significantly decreased in capillary-like microvessels. Collectively, our data identify PDGFR-ß as a novel cellular marker for leptomeningeal fibroblasts comprising the leptomeninges and perivascular adventitial cells of the subarachnoid and penetrating large-sized cortical vasculatures.

Engineering bio-mimetic humanized neurological constructs using acellularized scaffolds of cryopreserved meningeal tissues.

Spinal cord injury (SCI) is one of the most precarious conditions which have been one of the major reasons for continuous increasing mortality rate of SCI patients. Currently, there is no effective treatment modality for SCI patients posing major threat to the scientific and medical community. The available strategies don't mimic with the natural processes of nervous tissues repair/regeneration and majority of the approaches may induce the additional fibrotic or immunological response at the injury site and are not readily available on demand. To overcome these hurdles, we have developed a ready to use bioengineered human functional neurological construct (BHNC) for regenerative applications in SCI defects. We used cryopreserved meningeal tissues (CMT) for bioengineering these neurological constructs using acellularization and repopulation technology. The technology adopted herein generates intact neurological scaffolds from CMT and retains several crucial structural, biochemical and mechanical cues to enhance the regenerative mechanisms. The neurogenic differentiation on CMT scaffolds was almost similar to the freshly prepared meningeal scaffolds and mimics with the natural nervous tissue developmental mechanisms which offer intact 3D-microarchitecture and hospitable microenvironment enriched with several crucial neurotrophins for long-term cell survival and function. Functional assessment of developed BHNC showed highly increased positive staining for pre-synaptic granules of Synapsis-1 along with MAP-2 antibody with punctuate distribution in axonal regions of the neuronal cells which was well supported by the gene expression analysis of functional transcripts. Given the significant improvement in the field may enable to generate more such ready to use functional BHNC for wider applicability in SCI repair/regeneration.

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 (Aß). In AD, degeneration of neurons is preceded by the formation of Aß 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 Aß 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 Aß 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 Aß 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.

Different segments of the cerebral vasculature reveal specific endothelial specifications, while tight junction proteins appear equally distributed.

The identification of the "paucity of transportation vesicles" and "belt-like" tight junctions (TJs) of endothelial cells as the "morphological correlate of a blood-brain barrier" (BBB) by Reese and Karnovsky (J Cell Biol 34:207-217, 1967) has become textbook knowledge, and countless studies have helped to further define the elements, functions, and dynamics of the BBB. Most work, however, has focused on parenchymal capillaries or less clearly defined "microvessels", while a systematic study on similarities and differences between BBB architecture along the vascular tree within the brain and the meninges has been lacking. Since astrocytes induce endothelial cells to display BBB-typical characteristics by sonic hedgehog and Wnt/ß-catenin signaling, we hypothesized that BBB-typical features should be most pronounced in parenchymal capillaries, where endothelium and astrocytes are separated by a basement membrane only. In contrast, this intimate contact is absent in leptomeningeal vessels, thereby potentially affecting BBB architecture. However, here, we show that claudin-3, claudin-5, zonula occludens-1, and occludin as typical constitutes of BBB TJs are comparably distributed in all segments of the parenchymal and the meningeal vascular tree of C57Bl6 mice. While electron microscopy revealed equally occluded interendothelial clefts, arterial vessels of the brain parenchyma but not within the meninges exhibited significantly longer TJ overlaps compared to capillaries. The highest density of endothelial vesicles was found in arterial vessels. Thus, endothelial expression of BBB-typical TJ proteins is not reflected by the distance to surrounding astrocytes, but electron microscopy reveals significant differences of endothelial specification along different segments of the CNS vasculature.

Juxtacerebral Tissue Regeneration Potential: Telocytes Contribution.

It is well proved already that neurogenesis does take place in mammals' brain, including human brain. However, neurogenesis by itself is not able to compensate for brain tissue loss in serious neurological diseases, such as stroke, brain trauma or neurodegenerative disorders. Recent evidences show that neural stem cell niches are present not only in classical locations, such as subventricularor subgranular zones, but in other areas as well, including tissues contiguous to the brain (meninges and choroid plexus).In this chapter we revise the relationship of neural stem cells with interstitial cells (mainly telocytes), which we think is significant, and we describe what is known about the juxtacerebral tissue neurogenesis potential.

Afección del sistema nervioso central en la enfermedad relacionada con IgG4: descripción de un caso y revisión de la bibliografía / Central nervous system in IgG4-related disease: case report and literature review

Introducción. La enfermedad relacionada con IgG4 es una entidad clínica multisistémica recientemente descrita y que se presenta con diferentes manifestaciones clínicas. Los órganos que están afectados con mayor frecuencia son el páncreas, la vía biliar y las glándulas salivales, y es menos frecuente la afección del sistema nervioso central. Caso clínico. Mujer de 33 años con alteraciones cognitivas, alucinaciones, cefalea, síndrome convulsivo, sinusitis maxilar con afección ósea y evidencia de paquimeningitis y panhipopituitarismo, con biopsia meníngea que confirmó una enfermedad relacionada con IgG4, tras haberse descartado causas secundarias. Se inició tratamiento con glucocorticoides y azatioprina, sin recaídas después de 12 meses de seguimiento. Conclusiones. Se debe considerar el diagnóstico de enfermedad relacionada con IgG4 en casos de paquimeningitis hipertrófica e hipofisitis, incluso sin que se acompañen de otras manifestaciones sistémicas, siempre que se hayan descartado otras causas más frecuentes. El tratamiento de elección son los glucocorticoides, y puede ser necesario añadir otro inmunosupresor como ahorrador de esteroides y para evitar las recaídas. Se necesitan estudios prospectivos para evaluar las diferentes manifestaciones clínicas y paraclínicas y establecer los resultados del tratamiento a largo plazo (AU)

Introduction. IgG4-related disease is a recently described multisystemic clinical entity that can occur with different clinical manifestations. The most often affected organs are the pancreas, bile duct and salivary glands, with unusual central nervous system affection. Case Report. A 33 year old woman who presented with cognitive impairment, hallucinations, headache, convulsive syndrome, maxillary sinus inflammation with bone involvement and evidence of pachymeningitis and panhypopytuirarism with meningeal biopsy that confirmed IgG4-related disease, after ruling out secondary causes. Treatment was started with steroids and azathioprine without relapses after 12 months follow-up. Conclusions. IgG4-related disease should be considered in cases of hypertrophic pachymeningitis and hypophysitis especially when no other cause has been found, even if they are not accompanied by other systemic disease manifestations, having ruled out other common causes. The treatment of choice is glucocorticoids and it could be needed to add another immuno­suppressant agent as steroid sparing and to prevent relapses. Prospective studies are needed to evaluate the different clinical and paraclinical manifestations and to establish the results of long-term treatment (AU)

Lipid-laden cells differentially distributed in the aging brain are functionally active and correspond to distinct phenotypes.

We characterized cerebral Oil Red O-positive lipid-laden cells (LLC) of aging mice evaluating their distribution, morphology, density, functional activities and inflammatory phenotype. We identified LLC in meningeal, cortical and neurogenic brain regions. The density of cerebral LLC increased with age. LLC presenting small lipid droplets were visualized adjacent to blood vessels or deeper in the brain cortical and striatal parenchyma of aging mice. LLC with larger droplets were asymmetrically distributed in the cerebral ventricle walls, mainly located in the lateral wall. We also found that LLC in the subventricular region co-expressed beclin-1 or LC3, markers for autophagosome or autophagolysosome formation, and perilipin (PLIN), a lipid droplet-associated protein, suggesting lipophagic activity. Some cerebral LLC exhibited ß galactosidase activity indicating a senescence phenotype. Moreover, we detected production of the pro-inflammatory cytokine TNF-α in cortical PLIN(+) LLC. Some cortical NeuN(+) neurons, GFAP(+) glia limitans astrocytes, Iba-1(+) microglia and S100ß(+) ependymal cells expressed PLIN in the aging brain. Our findings suggest that cerebral LLC exhibit distinct cellular phenotypes and may participate in the age-associated neuroinflammatory processes.

Preparation of Amyloid Fibrils Seeded from Brain and Meninges.

Seeding of amyloid fibrils into fresh solutions of the same peptide or protein in disaggregated form leads to the formation of replicate fibrils, with close structural similarity or identity to the original fibrillar seeds. Here we describe procedures for isolating fibrils composed mainly of ß-amyloid (Aß) from human brain and from leptomeninges, a source of cerebral blood vessels, for investigating Alzheimer's disease and cerebral amyloid angiopathy. We also describe methods for seeding isotopically labeled, disaggregated Aß peptide solutions for study using solid-state NMR and other techniques. These methods should be applicable to other types of amyloid fibrils, to Aß fibrils from mice or other species, tissues other than brain, and to some non-fibrillar aggregates. These procedures allow for the examination of authentic amyloid fibrils and other protein aggregates from biological tissues without the need for labeling the tissue.

Segmental and restricted localization pattern of Fras1 in the developing meningeal basement membrane in mouse.

The Fras1/Frem family of extracellular matrix proteins consists of Fras1 and its structurally related proteins, Frem1 (Fras1-related extracellular matrix protein 1), Frem2 and Frem3. These are co-localized in embryonic epithelial basement membranes (BMs), where they contribute to epithelial-mesenchymal adhesion. Although Fras1 localization pattern in epithelial BMs has been well defined, it has not yet been comprehensively studied in the central nervous system. Here, we demonstrate the immunohistochemical profile of Fras1 in the developing mouse brain and reveal an exclusively meningeal BM protein deposition. Interestingly, Fras1 displays a segmental localization pattern, which is restricted to certain regions of the meningeal BM. Frem2 protein displays a similar localization pattern, while Frem3 is rather uniformly distributed throughout the meningeal BM. Fras1 and Frem2 proteins are detected in regions of the BM that underlie organizing centers, such as the roof plate (RP) of diencephalon, midbrain and hindbrain, and the RP-derived structures of telencephalon (choroid plexus and hem). Organizing centers exert their activity via the production of bioactive molecules, which are potential Fras1 ligands. The restricted pattern of Fras1 and Frem2 proteins indicates a molecular compartmentalization of the meningeal BM that could reflect, yet unspecified, functional and structural differences.

Extracranial projections of meningeal afferents and their impact on meningeal nociception and headache.

Headaches can be evoked by activation of meningeal nociceptors, but an involvement of pericranial tissues is debated. We aimed to examine a possible extracranial innervation by meningeal afferents in the rat. For in vivo neuronal tracing, dextran amines were applied to the periosteum underlying the temporal muscle. Labeling was observed 2 days later in the parietal dura mater, trigeminal ganglion, and spinal trigeminal nucleus with confocal and electron microscopy. In the hemisected rat head, extracellular recordings were made from meningeal nerve fibers. Release of calcitonin gene-related peptide (CGRP) from the cranial dura mater during noxious stimulation of pericranial muscles was quantified. In vivo capsaicin was injected into the temporal muscle while meningeal blood flow was recorded. In the parietal dura mater, labeled C- and Aδ fibers ramified extensively, accompanied the middle meningeal artery, and passed through the spinosus nerve into the maxillary and mandibular, but not the ophthalmic division of the trigeminal ganglion. Some fibers could be traced into the ipsilateral spinal trigeminal nucleus. Electrophysiological recordings revealed afferent fibers with mechanosensitive receptive fields both in the dura mater and in the parietal periosteum. Noxious stimulation of the temporal muscle caused CGRP release from the dura mater and elevated meningeal blood flow. Collaterals of meningeal nerve fibers project through the skull, forming functional connections between extra- and intracranial tissues. This finding offers a new explanation of how noxious stimulation of pericranial tissues can directly influence meningeal nociception associated with headache generation and why manual therapies of pericranial muscles may be useful in headaches.

Vascular alterations in PDAPP mice after anti-Aß immunotherapy: Implications for amyloid-related imaging abnormalities.

BACKGROUND: Clinical studies of ß-amyloid (Aß) immunotherapy in Alzheimer's disease (AD) patients have demonstrated reduction of central Aß plaque by positron emission tomography (PET) imaging and the appearance of amyloid-related imaging abnormalities (ARIA). To better understand the relationship between ARIA and the pathophysiology of AD, we undertook a series of studies in PDAPP mice evaluating vascular alterations in the context of central Aß pathology and after anti-Aß immunotherapy. METHODS: We analyzed PDAPP mice treated with either 3 mg/kg/week of 3D6, the murine form of bapineuzumab, or isotype control antibodies for periods ranging from 1 to 36 weeks and evaluated the vascular alterations in the context of Aß pathology and after anti-Aß immunotherapy. The number of mice in each treatment group ranged from 26 to 39 and a total of 345 animals were analyzed. RESULTS: The central vasculature displayed morphological abnormalities associated with vascular Aß deposits. Treatment with 3D6 antibody induced clearance of vascular Aß that was spatially and temporally associated with a transient increase in microhemorrhage and in capillary Aß deposition. Microhemorrhage resolved over a time period that was associated with a recovery of vascular morphology and a decrease in capillary Aß accumulation. CONCLUSIONS: These data suggest that vascular leakage events, such as microhemorrhage, may be related to the removal of vascular Aß. With continued treatment, this initial susceptibility period is followed by restoration of vascular morphology and reduced vulnerability to further vascular leakage events. The data collectively suggested a vascular amyloid clearance model of ARIA, which accounts for the currently known risk factors for the incidence of ARIA in clinical studies.

Meningeal-like organization of neural tissues in calanoid copepods (Crustacea).

Meninges, the connective tissue of the vertebrate central nervous system (CNS), have not been recognized in invertebrates. We describe the ultrastructure of the adult brain, antennules, and cord in five marine copepods: Calanus finmarchicus, Gaussia princeps, Bestiolina similis, Labidocera madurae, and Euchaeta rimana. In all of these locations we identified cell types with characteristics of the typical cells of vertebrate meninges and of their peripheral nervous system (PNS) connective tissue counterpart: fibroblasts, having flattened twisting processes with labyrinthine cavities communicating with the extracellular space, and macrophages, containing prominent lysosomes, well-developed endoplasmic reticulum, Golgi apparatus, and indented heterochromatin. The vertebrate distinction between electron-dense cells in the most external connective tissues (dura mater and epineurium) versus electron-lucent cells in the more internal connective tissues (pia-arachnoid and endoneurium-perineurium) was also found in the copepod CNS and PNS. Similar to the vertebrate organization, electron-dense cell networks penetrated from the outer layer (subcuticle) to surround inner substructures of the copepod nervous systems, and electron-lucent networks penetrated deeply from the brain and nerve surfaces to form intertwined associations with neural cells. Moreover, the association of these cells with basement membranes, glycocalyx, and fibrils of collagen in copepods conforms to a meningeal organization. The primary deviation from the vertebrate ultrastructural organization was the often tight investment of axons by the meningeal-like cells, with an intercalated basement membrane. Together, these data suggest that the tissues investing the copepod nervous system possess an organization that is analogous in many respects to that of vertebrate meninges.

Meningeal cells and glia establish a permissive environment for axon regeneration after spinal cord injury in newts.

BACKGROUND: Newts have the remarkable ability to regenerate their spinal cords as adults. Their spinal cords regenerate with the regenerating tail after tail amputation, as well as after a gap-inducing spinal cord injury (SCI), such as a complete transection. While most studies on newt spinal cord regeneration have focused on events occurring after tail amputation, less attention has been given to events occurring after an SCI, a context that is more relevant to human SCI. Our goal was to use modern labeling and imaging techniques to observe axons regenerating across a complete transection injury and determine how cells and the extracellular matrix in the injury site might contribute to the regenerative process. RESULTS: We identify stages of axon regeneration following a spinal cord transection and find that axon regrowth across the lesion appears to be enabled, in part, because meningeal cells and glia form a permissive environment for axon regeneration. Meningeal and endothelial cells regenerate into the lesion first and are associated with a loose extracellular matrix that allows axon growth cone migration. This matrix, paradoxically, consists of both permissive and inhibitory proteins. Axons grow into the injury site next and are closely associated with meningeal cells and glial processes extending from cell bodies surrounding the central canal. Later, ependymal tubes lined with glia extend into the lesion as well. Finally, the meningeal cells, axons, and glia move as a unit to close the gap in the spinal cord. After crossing the injury site, axons travel through white matter to reach synaptic targets, and though ascending axons regenerate, sensory axons do not appear to be among them. This entire regenerative process occurs even in the presence of an inflammatory response. CONCLUSIONS: These data reveal, in detail, the cellular and extracellular events that occur during newt spinal cord regeneration after a transection injury and uncover an important role for meningeal and glial cells in facilitating axon regeneration. Given that these cell types interact to form inhibitory barriers in mammals, identifying the mechanisms underlying their permissive behaviors in the newt will provide new insights for improving spinal cord regeneration in mammals.

Meninges in cancer imaging.

Primary malignant tumours arising from the meninges are distinctly uncommon, and when they occur, they are usually sarcomas. In contrast, metastatic meningeal involvement is increasingly seen as advances in cancer therapy have changed the natural history of malignant disease and prolonged the life span of cancer patients. The meninges can either be infiltrated by contiguous extension of primary tumours of the central nervous system, paranasal sinuses and skull base origin or can be diffusely infiltrated from haematogenous dissemination from distant primary malignancies. Imaging in these patients provides crucial information in planning management. This article reviews the pertinent anatomy that underlies imaging findings, discusses the mechanism of meningeal metastasis and highlights different imaging patterns of meningeal carcinomatosis and the pitfalls.

Mechanisms and targets for angiogenic therapy after stroke.

Stroke remains a major health problem worldwide, and is the leading cause of serious long-term disability. Recent findings now suggest that strategies to enhance angiogenesis after focal cerebral ischemia may provide unique opportunities to improve clinical outcomes during stroke recovery. In this mini-review, we survey emerging mechanisms and potential targets for angiogenic therapies in brain after stroke. Multiple elements may be involved, including growth factors, adhesion molecules and progenitor cells. Furthermore, cross talk between angiogenesis and neurogenesis may also provide additional substrates for plasticity and remodeling in the recovering brain. A better understanding of the molecular interplay between all these complex pathways may lead to novel therapeutic avenues for tackling this difficult disease.

Aracnoides trabecular, piamadre espinal humana y anestesia subaracnoidea / Trabecular arachnoid membrane, human spinal piamater and subarachnoid anesthesia

En los textos de anestesiología se aportan pocos detalles sobre la aracnoides trabecular y la piamadre espinal humana, a pesar de ser estructuras íntimamente relacionadas con los anestésicos locales administrados en una anestesia subaracnoidea. Complicaciones tales como el síndrome de cauda equina y el síndrome de irritación radicular transitorio posterior a la realización de bloqueos subaracnoideos, sumado a la alta permeabilidad que ha sido asociada con la piamadre, nos ha motivado a investigar sobre la ultraestructura de estas meninges. Método. Las muestras estudiadas se tomaron de cadáveres recientes y fueron examinadas por microscopía electrónica de transmisión y de barrido. Resultados. El trabeculado aracnoideo rodeaba a las raíces nerviosas, a la médula y a los vasos que se encontraban dentro del espacio subaracnoideo, limitando zonas. La piamadre estaba formada por un plano celular y por un compartimiento subpial. En el plano celular existían perforaciones naturales, especialmente en la región del cono medular y en las raíces nerviosas. Conclusiones. La inyección accidental de anestésicos locales dentro de las fundas que formaban el trabeculado aracnoideo podría justificar una dilución inadecuada de estas soluciones y el origen de síndromes neurotóxicos transitorios o permanentes. La alta permeabilidad de la piamadre podría deberse, en parte, a la existencia de perforaciones naturales, las cuales facilitarían un pasaje rápido de las sustancias introducidas en el líquido cefalorraquídeo hacia las raíces nerviosas y la médula espinal. En este caso, la membrana basal ubicada por debajo de las fibras colágenas del compartimiento subpial sería la única estructura limitante previa al tejido glio-neuronal de la médula.

Few details are to be found in anesthesiology texts concerning the trabecular arachnoid membrane and the human spinal pia mater in spite of being structures that are intimately related to local anesthetics administered in subarachnoid anesthesia. We were driven to investigate the ultrastructure of these meninges by complications such as the cauda equina syndrome and the transitory radicular irritation syndrome following subarachnoid blocks, added to the high permeability associated to the pia mater. Method. The samples analyzed were taken from recently deceased cadavers and were examined under transmission and scanning electron microscopy. Results. The arachnoid trabeculation surrounded the nerve roots, the spinal cord and the vessels within the subarachnoid space, limiting areas. The pia mater was formed by a cellular plane and by a sub-pial compartment. There were natural perforations in the cellular plane, particularly in the medullar cone region and the nerve roots. Conclusions. Accidental injection of local anesthetics into the sheaths formed by arachnoid trabeculation could be the cause of inadequate dilution of these solutions and the source of transitory or permanent neurotoxic syndromes. The high permeability of the pia mater could be partly due to the existence of natural perforations, which enable the quick passage of the substances introduced in the cerebrospinal fluid into the nerve roots and spinal cord. ln this case, the basal membrane located underneath the collagen fibers of the subpial compartment would be the only limiting structure before the glioneural tissue of the spinal cord.

Os textos de anestesiologia fornecem poucos detalhes sobre a aracnóide trabecular e a pia-máter espinhal humana, apesar delas serem estruturas intimamente relacionadas com os anestésicos locais administrados em uma anestesia subaracnóidea. Complicações tais como a síndrome de cauda eqüina e a síndrome de irritação radicular transitória posterior a bloqueios subaracnóideosas quais se soma a alta permeabilidade, que tem sido associada à pia-máter -levou-nos a pesquisar a ultraestrutura dessas meninges. Método. As amostras estudadas foram coletadas de cadáveres recentes e examinadas por microscopia eletrónica de transmissão e de varredura. Resultados. A trabeculação aracnóidea rodea va as raízes nervosas, a medula e os vasos no interior do espaço subaracnóide, limitando zonas. A pia-máter estava formada por um plano celular e um espaço subpial. No plano celular existiam perfurações naturais, especialmente na regiáo do cone medular e nas raízes nervosas. Conclusóes. A injeção acidental de anestésicos locais no interior das coberturas que formavam a trabeculação aracnoidea poderia justificar uma diluição inadequada das soluções e a origem de síndromes neurotóxicas transitórias ou permanentes. A causa da alta permeabilidade da pia-máter seria, em parte, a existencia de perfurações naturais que facilitariam a rápida passagem das substancias introduzidas no líquido cefalorraquiano para as raizes nervosas e a medula espinhal. Neste caso, a membrana basal localizada abaixo das fibras colágenas do espaço subpial seria a única estrutura limitante anterior ao tecido glio-neuronal da medula.

An experimental Staphylococcus aureus meningitis model for investigating induced leptomeningeal and subpial inflammation in rats: a transmission electron microscopy study.

OBJECTIVE: To evaluate leptomeningeal and subpial inflammatory responses of experimental Staphylococcus aureus bacteriemia following intraperitoneal and intravenous applications and to compare the inflammatory reactions in different regions of central nervous system. MATERIAL AND METHODS: Forty anesthetized rats were divided into four groups equal in number. The rats in group-I were given 1 ml suspension of Staphylococcus aureus intraperitoneally. Group-II was the control group of group I; it was administrated 1 ml 0.9% NaCl in water intraperitoneally. The rats in group-III were given the same amount of bacteria intravenously. Group IV was the control group of the group-III; it was administrated 1 ml 0.9% NaCl solution intravenously. The rats were sacrificed on the 21st day. Inflammatory changes of different regions of the central nervous system were examined under transmission electron microscopy. Statistical analysis was done by using variance analysis, Bonferroni, Tamhane post hoc, Student's t and univariate tests. RESULTS: Thoracic and occipital regions were the most vulnerable zones. Increasing of collagen tissue was the most detected inflammatory change. CONCLUSION: This experimental model can be used for inducing subpial and leptomeningeal inflammations and it may be developed for investigations of pathogenesis of leptomeningitis during systemic infections.

Spindle cell carcinoma of the external auditory meatus with intracranial extension: histological, immunohistochemical and electron microscopic evaluation.

We present a case of squamous spindle cell carcinoma of the external auditory meatus in a 38-year-old man. The tumour was extended to the inner ear, the temporal bone, the middle cranial fossa and the meningo-cerebral tissue. The surgical intervention of temporo-occipital craniotomy removed most of the neoplasia. At pathologic examination, the tumour showed an undifferentiated spindle cell pattern. Immunohistochemistry with a large antibody panel found a weak positivity only to EMA. The diagnosis was made when the electron microscopy showed rare junctional structures and tonofilaments.