Topographic and microscopic anatomical description of the emissary sinus of foramen ovale in adult humans.

OBJECTIVE: Although the Emissary Sinus of Foramen Ovale (ESFO) was first described by Trolard in 1868, its definition remains confused and neglected in the medical literature. This structure represents a vein, two veins, a venous plexus, or a dural sinus? Does it really exist? To understand this topic, this work aimed to describe the anatomy, topography, and microscopic features of the ESFO, precisely characterizing its structure, routes and anatomical correlations. PATIENTS AND METHODS: ESFO from the skull's base of adults were dissected into fifty anatomical blocks and evaluated using Hematoxylin and Eosin, Picro-sirius red and Weigert staining, and by Scanning Electron Microscopy (SEM). RESULTS: ESFO was always present between cavernous sinus and pterygoid plexus on both antimeres, its inferior route passing through the foramen ovale and/or sphenoidal emissary foramen (foramen of Vesalius), anterior to the mandibular branch of trigeminal nerve. Its microscopic arrangement resembled what was found on transverse sinus, that is composed by layers of collagen fibers oriented on transversal and longitudinal planes. It wasn't possible to identify the media and adventitial tunica, features seen in veins, and the elastic layer was very thin near its lumen. SEM analysis showed that, like the transverse sinus, the ESFO was composed by parallel cells that presented a rhombus shape containing central rounded nuclei. CONCLUSION: In summary, the venous channel passing through the foramen ovale and/or sphenoidal emissary foramen (foramen of Vesalius) is a dural venous sinus constituted by dura mater layers and should be considered during surgical approaches near the foramen ovale in the middle cranial fossa.

Straight sinus: ultrastructural analysis aimed at surgical tumor resection.

OBJECTIVE Accurate knowledge of the anatomy of the straight sinus (SS) is relevant for surgical purposes. During one surgical procedure involving the removal of part of the SS wall, the authors observed that the venous blood flow was maintained in the SS, possibly through a vein-like structure within the dural sinus or dural multiple layers. This observation and its divergence from descriptions of the histological features of the SS walls motivated the present study. The authors aimed to investigate whether it is possible to dissect the SS walls while keeping the lumen intact, and to describe the histological and ultrastructural composition of the SS wall. METHODS A total of 22 cadaveric specimens were used. The SS was divided into three portions: anterior, middle, and posterior. The characteristics of the SS walls were analyzed, and the feasibility of dissecting them while keeping the SS lumen intact was assessed. The thickness and the number of collagen fibers and other tissues in the SS walls were compared with the same variables in other venous sinuses. Masson's trichrome and Verhoeff's stains were used to assess collagen and elastic fibers, respectively. The data were analyzed using Zeiss image analysis software (KS400). RESULTS A vein-like structure independent of the SS walls was found in at least one of the portions of the SS in 8 of 22 samples (36.36%). The inferior wall could be delaminated in at least one portion in 21 of 22 samples (95.45%), whereas the lateral walls could seldom be delaminated. The inferior wall of the SS was thicker (p < 0.05) and exhibited less collagen and greater amounts of other tissues-including elastic fibers, connective tissue, blood vessels, and nerve fibers (p < 0.05)-compared with the lateral walls. Transmission electron microscopy revealed the presence of muscle fibers at a level deeper than that of the subendothelial connective tissue in the inferior wall of the SS, extending from its junction with the great cerebral vein to the confluence of sinuses. CONCLUSIONS The presence of a structure within the SS that can maintain the venous blood flow despite the dural wall might be considered an anatomical variation. The greater thickness of the inferior wall of the SS compared with the lateral walls is mainly due to the presence of larger amounts of tissues other than collagen. Delamination of the inferior wall of the SS was mostly possible in its inferior wall, but an attempt to delaminate the lateral walls is not recommended. Ultrastructural assessment corroborated a recent report of the presence of muscle fibers in the inferior wall of the SS.

Falcine venous plexus within the falx cerebri: anatomical and scanning electron microscopic findings and clinical significance.

BACKGROUND: Only limited attention has been paid to the anatomy and clinical importance of the falcine venous plexus. The aim of this study was to evaluate the falcine venous plexus anatomically using scanning electron microscopy (SEM), and to provide guidance for neurosurgical approaches. METHODS: Latex or ink was injected into the superior and inferior sagittal sinus. The falcine venous plexus lying within the connective tissue of the falx cerebri was observed by dividing the falx into thirds (anterior, middle and posterior). Further, the SEM appearance of the falcine venous plexus was evaluated. RESULTS: The anterior third of the falx cerebri consisted of small diameter falcine venous vessels. These vessels were localized close to either the superior or inferior sagittal sinus, and none extended as far as mid-falx cerebri levels in any of the 16 cases. They communicated with either superior or inferior sagittal sinuses, but not with both of these sinuses. In the middle third of the falx cerebri, the majority of the vessels of the falcine venous plexus had larger diameter compared to those of the anterior third. These vessels extended the length of the falx cerebri levels. They communicated with both superior and inferior sagittal sinuses. In the posterior third of the falx cerebri, the vessels of the falcine venous plexuses had the largest diameter and were located at the junction of the inferior sagittal sinus and the straight sinus. They were localized at the lower two-thirds of the falx cerebri. In all cases, the dense venous networks communicated with the inferior sagittal sinus but not with the superior sagittal sinus. The falcine venous plexus observed in the posterior third of the falx cerebri was denser than in the anterior and middle portions. The SEM revealed small vessels whose diameter ranged between 42 and 138 µm. The vessels of the falcine venous plexus in the anterior third had a mean diameter of 0.42 ± 0.1 mm, in the middle third a mean diameter of 0.87 ± 0.17 mm, and in the posterior third, 1.38 ± 0.21 mm. CONCLUSION: The falcine venous plexus is a network of venous channels that exists within the connective tissue of the falx; the sizes and patterns of communication of these structures showed regional differences. Neurosurgeons should be aware of the regional differences when making an incision or puncturing the falx during a surgical approach.

Junction between the great cerebral vein and the straight sinus: an anatomical, immunohistochemical, and ultrastructural study on 25 human brain cadaveric dissections.

The cerebral venous system is poorly understood, and best appreciated under macroscopic anatomical considerations. We present an anatomical and immunohistochemical studies to better define the morphological characteristics of the junction between the great cerebral vein and the straight sinus. Twenty-five cadaveric specimens from the anatomy laboratory of the University Victor Segalen of Bordeaux were studied. The observation of the venous junctions with the straight sinus was performed under an operating microscope. The smooth muscular actin immunohistochemical staining was performed for 18 veno-sinosal junctions. Five venous junctions were observed using an electron microscope. We observed 3 different anatomic aspects: type 1 was a junction with a small elevation in its floor and a posterior thickening (14 cases); type 2 was a junction with an outgrowth on the floor like a cornice (7 cases); and type 3 was a junction presenting a nodule. Microscopic study of type 1 and 2 junctions showed a positive coloration to orceine attesting the presence of elastic fibers. Immunohistochemistry revealed the presence of smooth muscular actin and S 100 protein attesting the presence of smooth muscular fibers and nervous fibers. We observed in the ultrastructural study, a morphological progression of the endothelium. The venous orifice of the great cerebral vein into the straight sinus could be anatomically assimilated as a true "sphincter." Its function in the regulation of the cerebral blood flow needs further exploration.

Mesoscopy and scanning electron microscopy of the trabecular projections in the superior sagittal sinus.

The trabecular projections of the human superior sagittal sinus were classified into types and subtypes according to spatial arrangement and shape. The horizontal and vertical projections direct laminar blood flow, while the conic type, which is avalvular, protects the openings of the superior cerebral veins in the superior sagittal sinus.

Three-dimensional and ultrastructural ICAM-1 distribution in the choroid plexus, arachnoid membrane and dural sinus of inflammatory rats induced by LPS injection in the lateral ventricles.

To investigate immunological environment in the cerebrospinal fluid (CSF) system, ultrastructural and three-dimensional localization of intercellular adhesion molecule-1 (ICAM-1) was studied in the choroid plexus, arachnoid membrane and dural sinus of LPS-stimulated rats with immuno-SEM and TEM. The choroid plexus epithelial cells expressed rich ICAM-1 along the microvilli. The arachnoid trabeculae fibroblast-like cells demonstrated ICAM-1 expression on both sides facing the subarachnoid space moderately. The dural sinus endothelial cells, however, showed only few ICAM-1 expression and no specific localization. These results suggest that the choroid plexus and arachnoid membrane may play an important mutual role for leukocyte migration in the CSF system, and that the CSF system may function in immunoreaction independently of the vascular system with the aid of up-regulated ICAM-1 expression.

[The relief of the luminal surface of the sinuses in the mammalian cranial dura mater]. / Rel'ef liuminal'noi poverkhnosti sinusov tverdoi obolochki mozga mlekopitaiushchikh.

In Mammalia with different types in organization of blood outflow in the dura mater venous sinuses: vertebral (tiger), jugular (fur-seal, cat, rabbit) and mixed (rat, dog, man) the internal surface relief of these sinuses has been studied. The total plan of the relief in all the species studied is principally the same. It is characterized with presence of visually determined macro-relief structures: Pacchionian bodies, trabeculae, bars, eminences and excavations in places, where the sinuses fuse, initial folds (micro-relief) and, at last, formations composed by the nucleus and the external membrane of endotheliocytes (ultra-relief). The micro-relief depends on the type of the venous outflow from the brain. In the animals with the jugular type of the outflow the longitudinal folds are more expressed; in the animals with the vertebral type--there occur folds with transversal orientation. For the representatives with the mixed type--multilayered elastic carcass is specific. At the same time, the development degree of the micro-relief with a similar type of blood outflow is different. The relief of the luminal surface of the longitudinal venous sinus of the mammalian dura mater is supposed to be determined by presence of extravascular formations, by the muscular structures tonus, by construction of the wall elastic carcass and by activity of the luminal part of the external membrane of endotheliocytes.

The endothelial surface of large veins of rabbit: scanning electron microscopic observations.

The following veins of the rabbit were fixed by perfusion and studied systematically by scanning electron microscopy: sagittal sinus, confluence of sinuses, external jugular vein, superior vena cava, inferior vena cava, greater saphenous, and femoral veins. One result is that the shape and arrangement of endothelial cells of the veins are obviously influenced by hemodynamic shear forces. Two types of subendothelial fibres were demonstrated: "cross-fibers" which correspond to the circular inner muscle cells of the media, and "longitudinal fibers" which correspond to the intimal meshwork of connective tissue fibers. Regional differences are demonstrated in the occurrence of these fibres. Moreover, five morphologically different venous valve types are observed. The functional significance of these different valve types is not yet known.

[The structure of meningeal granules based on light- and scanning electron microscopic studies]. / Beitrag zum Bau der Granula meningica auf Grund lichtmikroskopischer und rasterelektronenmikroskopischer Untersuchungen

The granula meningica of man (medium and advanced age) were investigated by means of light microscopy and scanning electron microscopy. We established the following: 1. The endothel of the sinus durae matris of man only seldom shows the blind tubes of endothel which were described by Andres (1967)1 after investigations made in cats and dogs. 2. a) There are no tube systems lined with mesothelial cells in the tissue of the granula meningica. Usually the cellcords and cellclusters are solid. Only in exceptional cases do they have a cavity. b) There are wide spaces between the collagen fibrebundles. These spaces are filled with a thinly liquid amorphous ground substance. We observed many free cells there (especially macrophages). 3. The construction of the connective tissue of the granula meningea lead us to conclude, that they are capable of changing their volume and shape considerably. The possible functional consequences of these results were discussed.