Dural Layer Research Articles

Linear arrays of homogenous mast cells in the dura mater of the rat

Using fluorescence histochemistry, 5-HT, histamine and heparin were colocalized in a large population of cells in the dura mater thereby identifying them as mast cells. In addition, because these cells were highly sensitive to compound 48/80 and were densely packed with granules of a consistent density, they were identified specifically as 'connective tissue' mast cells. Other types of mast cells, i.e. 'mucosal' or 'neurolipomastocytes', were not present in the rat dura mater. 5-HT immunohistochemistry was the best technique for demonstrating that there were populations of mast cells, one associated with each of the two layers of dura. Although shaped differently the type of mast cell in each layer was the same. It was observed that mast cell shape is dependent on the contiguity, density and orientation of its surrounding elements, not its type. In general, mast cells in the outer layer were aligned parallel to the middle meningeal artery and those in the inner layer were parallel to trigeminal nerve branches that coursed obliquely across the middle meningeal artery. Examination of cross-sections of dura revealed that most mast cells also were aligned at the interface between the two dural layers. The linear orientation of mast cells in two planes of each layer suggests a programmed lamellar seeding of these cells during development of the dura. This study also demonstrated that the majority of dural mast cells were more closely related to other connective tissue elements than to blood vessels and nerves. These results (1) are compatible with the suggestion that dural mast cells play a non-obligatory role in the neuroinflammatory response, (2) leave open to question the role of the dural mast cell in headache or the regulation of blood flow, and (3) support evidence that dural mast cells play an important role in connective tissue related functions, e.g. development, inflammatory response to injury and wound repair.

On the question of a subdural space

The structure of the meninges, with particular attention to the architecture of the inner portions of the dura mater and the arachnoid mater, has been reviewed in reference to the probable existence of a "subdural" space. The dura is composed of fibroblasts and large amounts of extracellular collagen. The innermost part of the dura is formed by the dural border cell layer. This layer is characterized by flattened cells with sinuous processes, extracellular spaces containing an amorphous material, and the presence of junctions between its cells. The dural border cell layer is continuous with the inner (meningeal) portions of the dura and may be attached to the underlying arachnoid by an occasional cell junction. The arachnoid consists of an outer part, the arachnoid barrier cell layer, and an inner portion, the arachnoid trabeculae which bridge the subarachnoid space. Arachnoid barrier cells are electron-lucent, closely apposed to each other, and joined by many cell junctions; in this layer there is little extracellular space and essentially no intercellular material. Arachnoid trabecular cells cross the subarachnoid space in a random manner, have extracellular collagen associated with their flattened processes, and form structures of variable shapes and sizes. There is no evidence of an intervening space between the arachnoid barrier cell layer and the dural border cell layer that would correlate with what has been called the subdural space. When a tissue space is created in this general area of the meninges it is the result of tissue damage and represents, in most instances, a cleaving open of the dural border cell layer. In this situation, extracellular spaces in the dural border cell layer are enlarged, cell junctions are separated, and it is probable that cell membranes are damaged. A survey of reports describing the morphology of the inner and outer capsule of so-called subdural hematomas in humans reveals that dural border cells are found in both parts of the capsule. Also, experimental infusion of blood into this portion of the meninges in animals frequently dissects open the dural border cell layer. These data support the view that what has been called a subdural hematoma is most frequently a lesion found within the layer formed by dural border cells. It is suggested that the so-called subdural space is not a "potential" space since the creation of a cleft in this area of the meninges is the result of tissue damage. In this respect it shares no similarities with legitimate potential spaces (i.e., serous cavities) found at other locations in the body.(ABSTRACT TRUNCATED AT 400 WORDS)

Subdural compartment in pig: A morphologic study with blood and horseradish peroxidase infused subdurally

The dura-arachnoid junction is examined in normal animals and in animals subjected to subdural infusion of blood immediately prior to death, simulating acute subdural hemorrhages. The Norwegian landrace pig is used as the experimental animal. Horseradish peroxidase (HRP) has been added to the injected blood to serve as a macromolecular tracer. The material is studied by light and electron microscopy. Special attention is given to the level of the induced subdural cleavage plane, the total distribution of the infused blood, and the natural sites of drainage. The dura-arachnoid junction, identified here as the subdural compartment (the dural border layer of others), consists of an avascular tissue with flake-like, relatively electron-lucent cells stacked upon each other in several layers with narrow intercellular clefts. Under normal conditions there is no evidence of a so-called "subdural space." When under the present experimental conditions bleeding takes place into this cellular tissue, it splits without any particular, predestined cleavage plane, although most often close to the fibrous matter of the dura. The bleeding extends throughout the cerebral and spinal parts of the compartment and also along the spinal nerve roots. Contamination of the subarachnoid space occurs only in some cases subjected to large infusions and apparently only at spinal levels. The HRP diffuses into the dura, but does not traverse the arachnoid barrier layer.

くも膜嚢腫と二重硬膜とを伴った特発性脊髄ヘルニアの一例

Idiopathic spinal cord herniation is very rare, 5 cases being so far reported in the literature. A 71-year-old-woman with a gradual loss of power in her left leg and with a sensory disturbance in the lateral side of her right leg was admmited. MRI showed that from Th4 to Th5, the spinal cord was shifted ventrally and disappeared, and a dilated subarachnoid space was noticed dorsally. She was diagnosed spinal cord herniation associated with an arachnoid cyst, and the operation was done. During operation, not only an intradural arachnoid cyst was obsreved dorsally, but was duplicated dura mater ventrally. In the ventral lesion, the spinal cord was herniated through a defect of the inner layer of the dura mater. This dural inner layer as well as the arachnoid cyst was resected. Her clinical symptoms were not progressed.When the spinal cord is shifted or disappeared in an image, we should precisely determine the relationship between the spinal cord and the dura mater during operation with consideration of a possibility of the presence of idiopathic spinal cord herniation.

Luteinizing hormone-releasing hormone (LHRH)-expressing cells do not migrate normally in an inherited hypogonadal (Kallmann) syndrome

Kallmann syndrome inherited hypogonadotropic hypogonadism with anosmia, is associated with an X-chromosome deletion at Xp 22.3. In a Kallmann fetus, we have found an absence of luteinizing hormone-releasing hormone (LHRH)-expressing cells in the brain despite dense clusters of LHRH cells and fibers in the nose. LHRH-containing cells and neurites end in a tangle beneath the forebrain, within the dural layers of the meninges, on the dorsal surface of the cribriform plate of the ethmoid bone. Normal fetal brains, matched for age and sex, had LHRH cells and fibers, as expected, in the hypothalamus and preoptic area. Since LHRH-expressing cells recently were discovered to migrate from the olfactory placode into the brain, it appears that the hypogonadotropism of the Kallmann syndrome can be accounted for by a failure of LHRH cells to migrate into the brain.

Morphogenesis of rat cranial meninges

The meninges of albino Wistar rat embryos, aged between the 11th embryonic day (ED) and birth, were sectioned using a specially constructed device. This technique permits optimal microanatomical preservation of all tissues covering the convexity of the brain: skin, muscle, cartilage or bone, and the meninges. At ED11, the zone situated between the epidermis and the brain is occupied by a mesenchymal network. At ED12, part of this delicate network develops as a dense outer cellular layer, while the remainder retains its reticular appearance, thus forming an inner layer (the future meningeal tissue). At ED13, the dura mater starts to differentiate. At ED14, the bony anlage of the skull can be identified, and along with the proceeding maturation of dura mater some fibrillar structures resembling skeletal muscle fibers appear in the developing arachnoid space. At ED15-17, a primitive interface zone - dura mater/arachnoid - is formed, comprised by an outer electronlucent and an inner electron-dense layer marking the outer aspect of the arachnoidal space. At ED18-19, the innermost cellular row of the inner dural layer transforms into neurothelium, which is separated from the darker arachnoidal cells by an electron-dense band. The arachnoidal trabecular zone with the leptomeningeal cells is formed at ED19. By the end of the prenatal period (ED20-21), its innermost part organizes into an inner arachnoidal layer and an outer and inner pial layer. The results from this study indicate (i) that dura mater and leptomeninges develop from an embryonic network of connective tissue-forming cells, and (ii) that the formation of cerebrospinal fluid (CSF)-containing spaces accompanies the differentiation of the meningeal cellular layers.

Microvascularization of the intracranial dura mater.

The authors have studied the microvascularization of the intracranial dura mater by microradiographic and histologic examination of 73 injected anatomic specimens. There exists a very abundant superficial arterial plexus which also serves to supply the inner table of the cranial vault. This plexus is continuous, even at the walls of the venous sinuses and the dural septa. The arteries are for the most part tortuous. The veins may be satellites of the arteries or, on the contrary, from a plexiform network passing through crevices in the interior of the dural layer. The walls of these veins consist only of an endothelium to be seen within the fibrous layer of the dura. Often, the arteries compress the venous lumen; this dangerous situation probably explains the frequent occurrence of arteriovenous fistulae of the dura mater, known by the name of dural fistulae.

The lateral wall of the cavernous sinus. With special reference to the nerves related to it.

In a study of the cavernous sinus in 70 specimens, the lateral wall of the sinus was found to be formed by two layers: a superficial, dural layer and a deep layer. The latter was formed by the sheaths of nerves III, IV, and V 1,2 plus a reticular membrane extending between the sheaths. This membrane was often incomplete, particularly between the sheaths of nerves III and IV above, and V1 below. These findings do not conform with the descriptions of a single dural layer of the lateral wall, with nerves III, IV, and V 1,2 embedded in it, nor to other descriptions showing the cavity of the sinus divided into two compartments by a septum close to the lateral wall, with nerves III, IV, and V1 located within the septum. In the present study, the superficial and the deep layers of the lateral wall were found to be loosely attached to each other and easy to separate. In no case was a superficial compartment of the sinus found to be present between the two layers, and the nerves were never found to be running embedded in the superficial layer.

Redevelopment of the calvaria after partial craniectomy in growing rabbits: the effect of altering dural continuity.

A circular calvariectomy procedure was performed on 24 New Zealand white rabbits at 6 weeks of age. In 12 animals, the continuity of the dura mater was interrupted. The remaining animals served as controls. The animals were sacrificed at intervals to document the regenerative potential of the altered dural tissues. The results of this experiment show that bone deposition leading to calvarial redevelopment is directly dependent upon the presence of the dura mater. In addition, the rate of deposition is apparently affected by dural continuity, animal age, and localized differences in the thickness of the dural layers. The redevelopment and patency of the cranial sutures are strongly influenced by alterations in the continuity of the dura mater.

ULTRASTRUCTURAL STUDIES OF THE MENINX

The menlnx of mature rabbits is constituted of dural, meningothelial and arachnoid layers. The meningothelial layer is composed of meningothelial basal cells and overlying subdural cells with curiously lobulated nuclei. Subdural cells contain numerous intracytoplasmic filaments and desmosome‐like structure, which are lacking in fibrocytes located just beneath the dura. The arachnoid layer shows a framework of the arachnoid cells, collagen bundles and vessels, and cisternae as a channel of cerebro‐spinal fluid are enclosed by the lacunar cell cords. The pia‐glial membrane separating the brain substance from the arachnoid is often complexly swirled together with the processes of marginal astrocytes.Subdural injection of Candida krussei produces suppurative and granulomatous foci, and the Intercellular spaces tend to be dilated by a retention of oedema fluid, blood or exudate. Intraarachnoid injection of the organisms also produces acute and chronic inflammatory changes, and the dissociation of lacunar cell cords at the desmosome‐like attachment may result in a widening and dilatation of the spaces. The meningothelial lining and pia‐glial membrane are considered to be a sort of barrier to protect the underlying tissue from various pathological changes.

Cranial venous system and the posterior fossa in spina bifida aperta

A study of the cerebral venous system in children with S.B.A. was undertaken, and this report concerns the gross structure of this structure of this system in the posterior fossa. Noteworthy is the closeness of the torcular to the foramen magnum. The lateral sinuses ran near to the foramen magnum to the sigmoid sinuses. The dura of the posterior fossa consisted of a plexiform structure in which no clear distinction could be made between various sinus systems normally present in the dural layers of the posterior fossa, thus constituting an occipital plexus. The walls of the sinuses were weak and were vulnerable to mechanical pressure. The foramen magnum of the skulls of children with S.B.A. was larger than in normal children. The distance of the torcular to the ventral margin of the foramen magnum was smaller in S.B.A. This distance remained unchanged at least until nine months of age in normal children as well as in children with S.B.A., although there was an increase in size of the foramen magnum in both with advancing age.

Structure of the human arachnoid granulation.

✓ The human arachnoid granulation was studied by light microscopy in gapless serial sections after local postmortem perfusion of the subarachnoid space with glutaraldehyde. The smaller granulations are invested in a dural sheath several layers thick which is separated from the body of the granulation by a true subdural space. In larger granulations, there are restricted regions where the body of the granulation protrudes through the dura to enter the venous sinus directly.

Reaction to injuries in the brain--an electron microscopic analysis of its topographical characteristics.

An electron microscopic observation of the central nervous system of adult rabbits in normal and pathological conditions was performed from the view‐point of histological topography.The meninges can be divided into 4 layers; 1st dural, 2nd subdural, 3rd meningothelial and 4th arachnoid layers, and the cellular components and responses of each layer were discussed in detail. The perivascular space of the penetrating vessels can be traced until the pia‐ glial border, but it is not clearly seen in the brain substance. An adventitial space containing adventitial cells and some collagen fibers is, however, recognized in the brain substance, and this is the site of proliferation of mesenchymal elements in various inflammatory conditions. The characteristics of degrading process in both the cerebral gray and white substances is also discussed. Through this investigation, an important role of the mesenchymo‐ectodermal junction in pathological conditions is emphasized, referring to the response of brain macrophages and perivascular astrocytes.

Progressive Obliteration of the Superior Orbital Fissure

A variety of periorbital ossifications are commonly found in "normal" human skulls (Kostowiecki, 1964). They are located predominately in the posterior part of the orbit and display various shapes and sizes. The most common ossifications, apart from the "spina recti lateralis," appear in the superior orbital or sphenoidal fissure. Some of them represent small, free pieces of thin bone located at the junction of periorbital and dural layers. Others grow upwards from the superior margin of the greater sphenoidal wing, which forms the lower margin of the lateral extension of the superior orbital fissure. Spicules which appear near the lateral end of the superior orbital fissure may embrace a sizeable foramen. This opening carries the superior ophthalmic vein as well as the arterial meningeo-orbital anastomosis between the lacrimal artery and the anterior ramus of the middle meningeal artery. The name "medial meningeo-orbital foramen" has been previously proposed for this aperture.

人胎児蝸牛小管及蝸牛窓の発生学的研究

The material consists of 7 human embryos which lengths range from 20mm to 16cm, inserting 22, 2 7, 35, 40 and 55mm long specimens between them. The youngest 20mm long embryo belongs to the Streeter's horizon XVIII developmental stage, in which three semicircular ducts and all the peripheral nerves to the sensory epithelium of the membranous labyrinth are distinct. Its otic capsule is cartilageous only in its vestibular part, its cochlear part remains precartilageous.In the next 22mm long embryo the cochlear part becomes also cartilageous, though not so much advanced as the vestibular part, and the fenestra perilymphatica becomes distinct which is in the previous stage of 20mm long specimens already only as a less dense area from the surrounding precartilageous tissue discernible (Fig. 1, 2, 3, Pl. 1)In this 22 and next 27mm long specimens the histological appearance of the medial and lateral margin of the fenestra perilymphatica is not the same. The surface of the lateral margin shows a dense mesenchymal layer, while that of the medial not.(Fig 4-5 Pl. 1)In the next 35mm long specimen appears a little fibrous characteristic in this dense mesenchymal layer of the lateral margin so that two fibrous layers in the opening radiating from the lateral margin medialward becomes distinct. These two layers in the opening have a less dense layer between them. The inner layer among the two is direct under the cochlear duct, the outer one continues medialward to that area, where canaliculus cochleae appears. These structures in 35mm long become more distinct in 40mm long one.(Fig. 9, Pl. 2, Fig. 15, Pl. 3)Streeter's periotic space begins to form already in 35mm long specimen and it becomes spacious neighbering fenestra vestibuli in the next 40mm long. But the space of the scala tympani is not yet to be seen, its spacious structure appears only in the next 55mm long specimen. In the latter not only the scala tympani, but also the scala vestibuli is very spacious in comparison with the cochlear duct.In the region of the fenestra perilymphatica is formed the cartilageous canaliculus cochleae, although very short, in this 55mm long embryo.Such formation of cartilageous canal begins already in 35mm long one, in which only as a cartilageous protrusion (Fig. 6-9, Pl 2*), in the next 40mm long one in the form of a cartilageous process (Fig. 11, Pl. 2, Fig. 11-14, Pl. 3*) under the mesenchymal anlage of the canaliculus (Fig. 9, Pl. 2, Fig. 15, Pl. 3°) from behind foreward. This cartilageous process may fuse with the cochlear part and make a canal.(Fig. 18-23, Pl. 4, Fig. 24-26, Pl. 5)This cartilageous canal of the canaliculus becomes long and covers almost all length of the mesenchymal aquaeductus canal in 16cm long embryo (Fig. 27-35, Pl. 5-6) As the cartilageous tube of this canal reaches near the scala tympani in this specimen, there appears a cartilageous process protruding to this end of the tube, This cartilageous process makes a new hinder rand of the fenestra cochleae and coming near the tympanic end of the canaliculus tube it does not fuse with the latter so that there remains a very narrow mesenchymal part which connects the two part canaliculus and fenestra cochleae. The same structure is also in the osseous capsule observable.The mesenchymal canaliculus begins to be formed. in 40mm long one as a continuation from the endocranial dural layer before the gangl. sup. of the glossopharyngeal nerve to the outer fibrous layer of the opening of the fenestra perilymphatica. This fibrous strand becomes in the next stage of 55mm long one a tube with fibrous wall, in which lumen there is some reticular structure. Such structure does not change in 16cm long one, its wall becomes thicker, its surrounding mesenchym is not so loose as that of the fenestra cochleae.The existence of the Waltner's barrier membrane is doubtful.

EXTENSIVE EROSION OF THE BASE OF THE SKULL FROM A LEPTOMENINGEAL CYST

EROSION of the cranial bones from pressure of a leptomeningeal cyst is an uncommon, but not rare, condition. While the majority of such cysts develop after severe trauma to the skull, usually with fracture, there is evidence that congenital abnormalities in the dura and leptomeninges may contribute to their production. Haymaker and Foster 1 reported a case in which a large collection of clear, colorless fluid resembling cerebrospinal fluid was found enclosed between the two layers of the dura in the posterior cranial fossa; a small defect was present beneath the tentorium, through which a lobule of the cerebellum was herniated. While their patient gave a history of a fracture of the skull in childhood, the separation of the dural layers and the small subtentorial defect may have been congenital abnormalities which favored development of a cyst in this location. Leptomeningeal cysts have been noted more commonly in the parietal,