Evaluation of fluid channels in the human dura and superior sagittal sinus in older patients.

AIM: Recent studies suggest the leptomeninges may have a lymphatic drainage system connecting the subarachnoid space with dorsal cervical lymph nodes. The distribution and histologic features of any dural "lymphatics" has not been established or extensively studied. MATERIAL AND METHODS: Duras from 113 patients were evaluated including 96 formalin-fixed dural samples (mean age 62 years) collected from 2010 to 2015. An additional 17 samples were collected from Alzheimer's disease (AD) patients (mean age 81) autopsied between 1995 and 1997. Two, 2 cm length coronal sections were taken from mid-convexity dura, parallel to the middle meningeal artery, 3-5 cm below and perpendicular to the superior sagittal sinus (SSS). Sections of twenty-two cases were also taken of the SSS and peri-SSS dura. To screen for possible lymphatics, 52 dural and 22 SSS samples from these cases were evaluated with CD31 and podoplanin (D240) immunohistochemistry. RESULTS: Numerous unlined microscopic channels were found in 101 of 113 (89 %). In non-AD duras, 86 of 92 (93 %) had numerous channels. Duras with AD had significantly less channels i.e. 15 of 21(71 %, P = 0.048). None of the channels had lymphocytes, or neutrophils in their lumena. In the superior sagittal sinus, 9 of 9 non-AD and 12/13 AD SSS duras had fluid channels. Congo red stains revealed no amyloid-like material in the AD duras. Immunohistochemically, CD31 was not found in fluid channels but was in endothelium in 36 of 36 non-AD duras and in most blood vessels including 16 of 16 AD patients. Seven of 36 (19 %) with non-AD and 1 of 16 (6%) with AD had podoplanin in thin walled vessels suggestive of lymphatics but none showed staining in fluid channels. CONCLUSIONS: Unlined fluid channels are present in the dura but not clearly lymphatic.

Radiation Disrupts the Protective Function of the Spinal Meninges in a Mouse Model of Tumor-induced Spinal Cord Compression.

BACKGROUND: Recent advances in multidisciplinary treatments for various cancers have extended the survival period of patients with spinal metastases. Radiotherapy has been widely used to treat spinal metastases; nevertheless, long-term survivors sometimes undergo more surgical intervention after radiotherapy because of local tumor relapse. Generally, intradural invasion of a spinal tumor seldom occurs because the dura mater serves as a tissue barrier against tumor infiltration. However, after radiation exposure, some spinal tumors invade the dura mater, resulting in leptomeningeal dissemination, intraoperative dural injury, or postoperative local recurrence. The mechanisms of how radiation might affect the dura have not been well-studied. QUESTIONS/PURPOSES: To investigate how radiation affects the spinal meninges, we asked: (1) What is the effect of irradiation on the meningeal barrier's ability to protect against carcinoma infiltration? (2) What is the effect of irradiation on the meningeal barrier's ability to protect against sarcoma infiltration? (3) What is the effect of irradiation on dural microstructure observed by scanning electron microscopy (SEM)? (4) What is the effect of irradiation on dural microstructure observed by transmission electron microscopy (TEM)? METHODS: Eighty-four 10-week-old female ddY mice were randomly divided into eight groups: mouse mammary tumor (MMT) implantation 6 weeks after 0-Gy irradiation (nonirradiation) (n = 11), MMT implantation 6 weeks after 20-Gy irradiation (n = 10), MMT implantation 12 weeks after nonirradiation (n = 10), MMT implantation 12 weeks after 20-Gy irradiation (n = 11), mouse osteosarcoma (LM8) implantation 6 weeks after nonirradiation (n = 11), LM8 implantation 6 weeks after 20-Gy irradiation (n = 11), LM8 implantation 12 weeks after nonirradiation (n = 10), and LM8 implantation 12 weeks after 20-Gy irradiation (n = 10); female mice were used for a mammary tumor metastasis model and ddY mice, a closed-colony mice with genetic diversity, were selected to represent interhuman diversity. Mice in each group underwent surgery to generate a tumor-induced spinal cord compression model at either 6 weeks or 12 weeks after irradiation to assess changes in the meningeal barrier's ability to protect against tumor infiltration. During surgery, the mice were implanted with MMT (representative of a carcinoma) or LM8 tumor. When the mice became paraplegic because of spinal cord compression by the growing implanted tumor, they were euthanized and evaluated histologically. Four mice died from anesthesia and 10 mice per group were euthanized (MMT-implanted groups: MMT implantation occurred 6 weeks after nonirradiation [n = 10], 6 weeks after irradiation [n = 10], 12 weeks after nonirradiation [n = 10], and 12 weeks after irradiation [n = 10]; LM8-implanted groups: LM8 implantation performed 6 weeks after nonirradiation [n = 10], 6 weeks after irradiation [n = 10], 12 weeks after nonirradiation [n = 10], and 12 weeks after irradiation [n = 10]); 80 mice were evaluated. The spines of the euthanized mice were harvested; hematoxylin and eosin staining and Masson's trichrome staining slides were prepared for histologic assessment of each specimen. In the histologic assessment, intradural invasion of the implanted tumor was graded in each group by three observers blinded to the type of tumor, presence of irradiation, and the timing of the surgery. Grade 0 was defined as no intradural invasion with intact dura mater, Grade 1 was defined as intradural invasion with linear dural continuity, and Grade 2 was defined as intradural invasion with disruption of the dural continuity. Additionally, we euthanized 12 mice for a microstructural analysis of dura mater changes by two observers blinded to the presence of irradiation. Six mice (three mice in the 12 weeks after nonirradiation group and three mice in the 12 weeks after 20-Gy irradiation group) were quantitatively analyzed for defects on the dural surface with SEM. The other six mice (three mice in the 12 weeks after nonirradiation group and three mice in the 12 weeks after 20-Gy irradiation group) were analyzed for layer structure of collagen fibers constituting dura mater by TEM. In the SEM assessment, the number and size of defects on the dural surface on images (200 µm × 300 µm) at low magnification (× 2680) were evaluated. A total of 12 images (two per mouse) were evaluated for this assessment. The days from surgery to paraplegia were compared between each of the tumor groups using the Kruskal-Wallis test. The scores of intradural tumor invasion grades and the number of defects on dural surface per SEM image were compared between irradiation group and nonirradiation group using the Mann-Whitney U test. Interobserver reliabilities of assessing intradural tumor invasion grades and the number of dural defects on the dural surface were analyzed using Fleiss'κ coefficient. P values < 0.05 were considered statistically significant. RESULTS: There was no difference in the median (range) time to paraplegia among the MMT implantation 6 weeks after nonirradiation group, the 6 weeks after irradiation group, the 12 weeks after nonirradiation group, and the 12 weeks after irradiation group (16 days [14 to 17] versus 14 days [12 to 18] versus 16 days [14 to 17] versus 14 days [12 to 15]; χ2 = 4.7; p = 0.19). There was also no difference in the intradural invasion score between the MMT implantation 6 weeks after irradiation group and the 6 weeks after nonirradiation group (8 of 10 Grade 0 and 2 of 10 Grade 1 versus 10 of 10 Grade 0; p = 0.17). On the other hand, there was a higher intradural invasion score in the MMT implantation 12 weeks after irradiation group than the 12 weeks after nonirradiation group (5 of 10 Grade 0, 3 of 10 Grade 1 and 2 of 10 Grade 2 versus 10 of 10 Grade 0; p = 0.02). Interobserver reliability of assessing intradural tumor invasion grades in the MMT-implanted group was 0.94. There was no difference in the median (range) time to paraplegia among in the LM8 implantation 6 weeks after nonirradiation group, the 6 weeks after irradiation group, the 12 weeks after nonirradiation group, and the 12 weeks after irradiation group (12 days [9 to 13] versus 10 days [8 to 13] versus 11 days [8 to 13] versus 9 days [6 to 12]; χ2 = 2.4; p = 0.50). There was also no difference in the intradural invasion score between the LM8 implantation 6 weeks after irradiation group and the 6 weeks after nonirradiation group (7 of 10 Grade 0, 1 of 10 Grade 1 and 2 of 10 Grade 2 versus 8 of 10 Grade 0 and 2 of 10 Grade 1; p = 0.51), whereas there was a higher intradural invasion score in the LM8 implantation 12 weeks after irradiation group than the 12 weeks after nonirradiation group (3 of 10 Grade 0, 3 of 10 Grade 1 and 4 of 10 Grade 2 versus 8 of 10 Grade 0 and 2 of 10 Grade 1; p = 0.04). Interobserver reliability of assessing intradural tumor invasion grades in the LM8-implanted group was 0.93. In the microstructural analysis of the dura mater using SEM, irradiated mice had small defects on the dural surface at low magnification and degeneration of collagen fibers at high magnification. The median (range) number of defects on the dural surface per image in the irradiated mice was larger than that of nonirradiated mice (2 [1 to 3] versus 0; difference of medians, 2/image; p = 0.002) and the median size of defects was 60 µm (30 to 80). Interobserver reliability of assessing number of defects on the dural surface was 1.00. TEM revealed that nonirradiated mice demonstrated well-organized, multilayer structures, while irradiated mice demonstrated irregularly layered structures at low magnification. At high magnification, well-ordered cross-sections of collagen fibers were observed in the nonirradiated mice. However, disordered alignment of collagen fibers was observed in irradiated mice. CONCLUSION: Intradural tumor invasion and disruptions of the dural microstructure were observed in the meninges of mice after irradiation, indicating radiation-induced disruption of the meningeal barrier. CLINICAL RELEVANCE: We conclude that in this form of delivery, radiation is associated with disruption of the dural meningeal barrier, indicating a need to consider methods to avoid or limit Postradiation tumor relapse and spinal cord compression when treating spinal metastases so that patients do not experience intradural tumor invasion. Surgeons should be aware of the potential for intradural tumor invasion when they perform post-irradiation spinal surgery to minimize the risks for intraoperative dural injury and spinal cord injury. Further research in patients with irradiated spinal metastases is necessary to confirm that the same findings are observed in humans and to seek irradiation methods that prevent or minimize the disruption of meningeal barrier function.

Scanning Electron Microscopic Observation of Myodural Bridge in the Human Suboccipital Region.

STUDY DESIGN: A scanning electron microscopic study performed on three cadaveric specimens focused on the human suboccipital region, specifically, myodural bridge (MDB). OBJECTIVE: This study showed the connection form of the MDB among the suboccipital muscles, the posterior atlanto-occipital membrane (PAOM) and the spinal dura mater (SDM), and provided an ultrastructural morphological basis for the functional studies of the MDB. SUMMARY OF BACKGROUND DATA: Since the myodural bridge was first discovered by Hack, researches on its morphology and functions had been progressing continuously. However, at present, research results about MDB were still limited to the gross anatomical and histological level. There was no research report showing the MDB's ultrastructural morphology and its ultrastructural connection forms between PAOM and SDM. METHODS: A scanning electron microscope (SEM) was used to observe the connection of myodural bridge fibers with PAOM and SDM in atlanto-occipital and atlanto-axial interspaces, and the connection forms were analyzed. RESULTS: Under the SEM, it was observed that there were clear direct connections between the suboccipital muscles and the PAOM and SDM in the atlanto-occipital and atlanto-axial spaces. These connections were myodural bridge. The fibers of the myodural bridge merged into the spinal dura mater and gradually became a superficial layer of the spinal dura mater. CONCLUSION: MDB fibers merged into the SDM and became part of the SDM in the atlanto-occipital and atlanto-axial space. MDB could transfer tension and pulling force to the SDM effectively, during the contraction or relaxation of the suboccipital muscles. LEVEL OF EVIDENCE: N/A.

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.

Analysis of dural sac thickness in the human cervical spine.

The thickness of the dura mater in the human cervical spine can vary between individuals and by vertebral level; these differences can result in various clinical outcomes. The purpose was to measure and analyze cervical dura mater thickness. Microscopic measurements were made of tissue from human cadavers. The subjects were nine human cadavers with no previous history of spinal deformity or surgery. Fourteen segments of both anterior and posterior dura mater from the C1 to C7 cervical vertebrae were obtained. Dura mater thickness was measured using an infrared laser-based confocal microscope. Statistical analyses were performed to examine the relationships of cervical dura mater thickness with vertebral level, age, and sex. The overall average cervical dura mater thickness was 379.3 × 10-3 mm. Statistically significant differences in thickness were found between the anterior and posterior segments (P < 0.0001). Moreover, the thickness at each vertebral level was significantly different from the thicknesses at the other levels (P < 0.05). The posterior dura mater thickness was highest at C1 and lowest at C5/6. Posterior dura mater thickness was significantly different at the axial, sub-axial, and lower cervical levels, whereas anterior dura mater thickness was relatively constant among levels. A significant correlation was found between thickness and age (P < 0.05); however, the average dura mater thickness was not significantly different between males and females. This study shows anatomical differences in cervical dura mater thickness with respect to vertebral level and age. These results provide anatomical information that will inform basic research and clinical approaches.

A novel biomimetic composite substitute of PLLA/gelatin nanofiber membrane for dura repairing.

OBJECTIVE: Biomimetic design will significantly improve growth and regeneration of dural cells and tissue for better repairing effects and fewer complications in repairing the native dura. This study designed a novel composite, biomimetic substitute based on the characteristics of native dura extracellular matrix. METHODS AND RESULTS: This substitute is expected to rapidly induce cell adhesion, migration, and fast regeneration of neotissue. The material characteristics (contact angle, surface charge, and zeta potential were evaluated), in vitro biological characteristics (cell stretch, connections between cells, cell proliferation) and in vivo tissue regeneration capability of this substitute were evaluated, compared to those of collagen dura substitute, the mostly used dura substitute. The results showed that the surface properties of this composite substitute were more biomimetic to native extracellular matrix than collagen substitute did, together with better cytocompatibility, tissue ingrowth, and neoangiogenesis. This composite substitute further demonstrated in clinical case study its ideal repair effect with no CSF leakage or other adverse reactions. CONCLUSION: In conclusion, the new biomimetic composite substitute provides alternative substitute for dura repairing.

Construction and in vitro testing of a cellulose dura mater graft.

INTRODUCTION: Cerebrospinal fluid (CSF) leaks are a common complication after cranial and spinal surgery and are associated with increased morbidity. Despite continuous research in this field, this problem is far from solved. In this paper, we describe the construction and testing of a bacterial cellulose (BC) membrane as a new dural patch. MATERIALS AND METHODS: The synthesis of BC was performed using Gluconacetobacter hansenii (ATCC 23769) and films were sterilized by autoclaving. The membranes were seeded with human dural fibroblasts. Growth, shape, and cell viability were assessed after 4 weeks. RESULTS: Normally shaped fibroblasts were seen on the BC grafts; confocal microscopy showed cells inside the structure of the mesh. Both viable and nonviable cells were present. Cellular attachment and viability were confirmed by replating of the membranes. DISCUSSION: BC membranes are used in clinical practice to improve skin healing. In the presence of water, they form an elastic, nontoxic, and resistant biogel that can accommodate collagen and growth factors within their structure, thus BC is a good candidate for dural graft construction.

Transmission electron microscope evidence of telocytes in canine dura mater.

Telocytes (TCs) are a novel type of interstitial cells present in a wide variety of organs and tissues (www.telocytes.com). Telocytes are identified morphologically by a small cell body and specific long prolongations (telopodes) alternating thin segments (podomers) with dilations (podoms). The presence of TCs in rat meninges has been identified in previous research. We here present further evidence that TCs existed in canine dura mater, closed to capillary and surrounded by a great deal of collagen fibres under transmission electron microscope.

In Vitro infection of human dura-mater fibroblasts with Staphylococcus aureus: colonization and reactive production of IL-1beta.

OBJECTIVE: Post-operative meningitis, caused mainly by Staphylococcus aureus and Gram-negative rods, is a life-threatening complication after neurosurgery, and its pathogenesis is far from clear. The purpose of this work was to study the experimental infection of human dura-mater fibroblasts and whole human dura by S. aureus. METHODS: In vitro cultures of human dura-mater fibroblasts and organotypic cultures of small pieces of human dura mater were inoculated with a human-derived S. aureus strain. The pattern of bacterial infection as well as cytokines secretion by the infected fibroblasts was studied. RESULTS: Our results suggest that colonisation of human dura-mater fibroblasts in culture and whole dura-mater tissue by S. aureus includes bacterial growth on the cell surface, fibroblast intracellular invasion by bacteria and a significant synthesis of interleukin 1beta (IL-1beta) by the infected cells. CONCLUSION: This is the first report of human dura-mater fibroblast infection by S. aureus. Hopefully, these results can lead to a better understanding of the pathogenesis of meningitis caused by this bacterial species and to a more rational therapeutic approach.

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.

Experimental syringohydromyelia induced by adhesive arachnoiditis in the rabbit: changes in the blood-spinal cord barrier, neuroinflammatory foci, and syrinx formation.

There are many histological examinations of syringohydromyelia in the literature. However, there has been very little experimental work on blood permeability in the spinal cord vessels and ultrastructural changes. We prepared an animal model of spinal adhesive arachnoiditis by injecting kaolin into the subarachnoid space at the eighth thoracic vertebra of rabbits. The animals were evaluated 4 months later. Of the 30 rabbits given kaolin injection into the cerebrospinal fluid, 23 showed complete circumferential obstruction. In the 7 animals with partial obstruction of the subarachnoid space, intramedullary changes were not observed. However, among the 23 animals showing complete obstruction of the subarachnoid space, dilatation of the central canal (hydromyelia) occurred in 21, and intramedullary syrinx (syringomyelia) was observed in 11. In animals with complete obstruction, fluorescence microscopy revealed intramedullary edema around the central canal, extending to the posterior columns. Electron microscopy of hydromyelia revealed a marked reduction of villi on the ependymal cells, separation of the ependymal cells, and cavitation of the subependymal layer. The dilated perivascular spaces indicate alterations of fluid exchange between the subarachnoid and extracellular spaces. Syringomyelia revealed that nerve fibers and nerve cells were exposed on the surface of the syrinx, and necrotic tissue was removed by macrophages to leave a syrinx. Both pathologies differ in their mechanism of development: hydromyelia is attributed to disturbed reflux of cerebrospinal fluid, while tissue necrosis due to disturbed intramedullary blood flow is considered to be involved in formation of the syrinx in syringomyelia.

Unintentional subdural placement of epidural catheters during attempted epidural anesthesia: an anatomic study of spinal subdural compartment.

BACKGROUND: Although infrequent, subdural block is a complication of epidural anesthesia with obvious implications. Knowledge of the spinal subdural compartment (dura-arachnoid interface) may help elucidate controversies arising from evidence that subdural catheter placement is feasible and may be difficult to identify clinically. METHODS: Samples of arachnoid lamina obtained during in vivo lumbosacral surgery (n = 4) and from cadavers (n = 6) were obtained and prepared for transmission electron microscopy and scanning electron microscopy. Subdural spaces were artificially produced in suitable samples, and an epidural catheter was inserted between the arachnoid and dura to compare the dimensions of meninges in relation to epidural catheters. RESULTS: Scanning electron microscopy of the dural sac showed areas of continuity between the arachnoid lamina and dura mater and other parts with both membranes separated by a subdural space. Transmission electron microscopy allowed the study of such border zones, where alternating cellular and collagen layers could be seen. A layer rich in collagen fibers and some fibroblasts separated arachnoid and neurothelial cells (dural border cells). Few specialized membrane junctions were found among cells adjacent to collagen fibers. Dura mater had an average thickness of 260 to 400 µm, with a dural lamina of approximately 4 to 6 µm. In areas where the arachnoid appeared separated from the dural lamina, its thickness measured 35 to 45 µm. Catheters with a diameter of 700 µm were successfully inserted inside the subdural space, between the dura mater and the arachnoid lamina. CONCLUSIONS: Dura mater and arachnoid layers act as a single unit but may be pulled apart by traction forces during cadaver processing of the dural sac or in vivo placement of catheters. This generates subdural spaces, either parallel or concentric, because of the minimal resistance offered by the tissue, which may be explained by its few specialized membrane junctions.

The collagenic architecture of human dura mater.

OBJECT: Human dura mater is the most external meningeal sheet surrounding the CNS. It provides an efficient protection to intracranial structures and represents the most important site for CSF turnover. Its intrinsic architecture is made up of fibrous tissue including collagenic and elastic fibers that guarantee the maintenance of its biophysical features. The recent technical advances in the repair of dural defects have allowed for the creation of many synthetic and biological grafts. However, no detailed studies on the 3D microscopic disposition of collagenic fibers in dura mater are available. The authors report on the collagenic 3D architecture of normal dura mater highlighting the orientation, disposition in 3 dimensions, and shape of the collagen fibers with respect to the observed layer. METHODS: Thirty-two dura mater specimens were collected during cranial decompressive surgical procedures, fixed in 2.5% Karnovsky solution, and digested in 1 N NaOH solution. After a routine procedure, the specimens were observed using a scanning electron microscope. RESULTS: The authors distinguished the following 5 layers in the fibrous dura mater of varying thicknesses, orientation, and structures: bone surface, external median, vascular, internal median, and arachnoid layers. CONCLUSIONS: The description of the ultrastructural 3D organization of the different layers of dura mater will give us more information for the creation of synthetic grafts that are as similar as possible to normal dura mater. This description will be also related to the study of the neoplastic invasion.

Histological and biomechanical study of dura mater applied to the technique of dura splitting decompression in Chiari type I malformation.

Many techniques are described to treat Chiari type I malformation. One of them is a splitting of the dura, removing its outer layer only to reduce the risks of cerebrospinal fluid (CSF) leak. We try to show the effectiveness of this technique from histological and biomechanical observations of dura mater. Study was performed on 25 posterior fossa dura mater specimens from fresh human cadavers. Dural composition and architecture was assessed on 47 transversal and sagittal sections. Uniaxial mechanical tests were performed on 22 dural samples (15 entire, 7 split) to focus on the dural macroscopic mechanical behavior comparing entire and split samples and also to understand deformation mechanisms. We finally created a model of volume expansion after splitting. Dura mater was composed of predominant collagen fibers with a few elastin fibers, cranio-caudally orientated. The classical description of two distinct layers remained inconstant. Biomechanical tests showed a significant difference between entire dura, which presents an elastic fragile behavior, with a small domain where deformation is reversible with stress, and split dura, which presents an elasto-plastic behavior with a large domain of permanent strain and a lower stress level. From these experimental results, the model showed a volume increase of approximately 50% below the split area. We demonstrated the capability of the split dura mater to enlarge for suitable stress conditions and we quantified it by biomechanical tests and experimental model. Thus, dural splitting decompression seems to have a real biomechanical substrate to envision the efficacy of this Chiari type I malformation surgical technique.

Cefalea pospunción dural. Ultraestructura de las lesiones durales y agujas espinales usadas en las punciones lumbares / Post dural puncture cephalea. UItra-structure of the dural lesions and spinal needles used in lumbar punctures

Con el microscopio electrónico de barrido, se examinó la morfología de las lesiones durales y aracnoideas en muestras de saco dura-aracnoideo extraídos de cuerpos humanos recién fallecidos. Después de hacer punciones con agujas Quincke y Whitacre 22-G y 25-G, no se encontraron diferencias estadísticamente significativas entre las áreas de las lesiones durales y aracnoideas. La lesión tenía una morfología diferente con cada aguja. La aguja Whitacre producía una lesión de bordes rotos con gran destrucción de fibras durales, mientras que la aguja "biselada" Quincke causaba una lesión con forma de "U" o "V", como la tapa de una lata, con bordes de corte limpio. La alineación paralela o perpendicular entre el bisel de la punta de la aguja Quincke y el eje del axis no modificaba el área de las lesiones durales y aracnoideas. Se analizó cómo se puede producir cada tipo de lesión y se interpretaron los otros factores que podrían participar. Con la misma técnica se estudiaron agujas espinales nuevas obteniéndose, en cierto porcentaje de éstas, una imagen tridimensional a gran aumento de la fragmentación de puntas, defectos del pulido y existencia de rebabas. Se analizó cómo se pueden alterar las puntas de las agujas al chocar contra el hueso y de qué manera los defectos de estas constituyen otro aspecto de la compleja suma de variables que predisponen a la aparición de una cefalea pospunción dural.

The morphology of dural and arachnoid lesions was electronically scanned, from samples of dura-arachnoid sacs taken from recently deceased human beings. After punctures with Quincke y Whitacre 22-G y 25-G needles, no statistically significant differences were found between the areas of the dural and arachnoid lesions. The lesion had a different morphology with each needle. The Whitacre needle produced a lesion of broken edges with great destruction of the dural fibers, whereas the Quincke "beveled" needle caused a "U" or "V" shaped lesion, like the lid of a can, with clean-cut edges. The parallel or perpendicular alignment between the bevel of the Quincke needle tip and the axis of the axis did not modify the area of the dural and arachnoid lesions. A study was made of how each type of lesion could have come about and of other possible participating factors. The same technique was used to study new spinal needles and, in a certain percentage, a three dimensional image was obtained, showing a great increase in the fragmentation of the tips, burnish defects and the existence of burrs. We also analyzed how hitting against the bone could affect the tips of the needles and how their defects could be another factor in the complex sum of variables that predispose the patient to suffer post dural puncture cephalea.

Com o microscópio eletrônico de varredura, examinou-se a morfologia das lesoes durais e da aracnóide em amostras de saco dural-aracnóideo extraídos de corpos humanos de recem-falecidos. As diferencas entre as áreas das lesoes durais e da aracnóide pós-puncao com agulhas Quincke e Whitacre 22-G e 25-G nao foram estatisticamente significativas, e a morfologia da lesao causada com cada agulha foi diferente. A agulha Whitacre provocou lesao de bordas rompidas com grande destruicao de fibras durais, enquanto a agulha "biselada" Quincke causou lesao com forma de "U" ou "V", como a tampa de uma lata, com bordas de corte limpo. O alinhamento paralelo ou perpendicular do bisel da ponta da agulha Quincke com o eixo do áxis nao modificou a área das lesóes durais e da aracnóide. Foram analisadas as causas de cada tipo de lesao e interpretados outros fatores envolvidos. Utilizando a mesma técnica, avaliaram-se imagens tridimensionais de algumas agulhas espinhais novas tiradas com grande aumento: fragmentacao das pontas, defeitos de polimento e presenca de rebarbas. Avaliou-se também como se modificam as pontas das agulhas ao atingirem o osso e a influência dos defeitos das pontas na complexa soma de variáveis que predispoem o aparecimento de cefaléia pós-puncao dural.

El saco dural humano. Morfología de la dura-aracnoides espinal. Origen del espacio subdural espinal / The human dural sac. Morphology of the spinal dura-arachnoid membrane. Origin of the spinal subdural space

Esta revisión resume los hallazgos encontrados en el saco dural de cadáveres de recién fallecidos estudiados con diferentes técnicas histológicas. El saco dural espinal está formado por tres estructuras concéntricas: la duramadre, que ocupa el 85-90 por ciento de su espesor, del lado externo; el compartimiento subdural, integrado por células neuroteliales, y la lámina aracnoidea, que ocupa el 5 al 8 por ciento interno. La duramadre, que consta de aproximadamente 80 láminas durales concéntricas, es una estructura permeable y fibrosa, por lo cual posee resistencia mecánica. El compartimiento subdural es una estructura concéntrica, celular, de resistencia mecánica muy baja, donde se pueden producir fisuras concéntricas por rotura de las células neuroteliales dando origen a un espacio subdural adquirido. La lámina aracnoidea es una estructura celular con mayor resistencia mecánica que el compartimiento subdural. Sus células están firmemente unidas por uniones especializadas de membrana y forman una barrera semipermeable que regula el pasaje de sustancias a través del espesor del saco dural.

El saco dural humano. Morfología de la dura-aracnoides espinal. Origen del espacio subdural espinal / The human dural sac. Morphology of the spinal dura-arachnoid membrane. Origin of the spinal subdural space

Esta revisión resume los hallazgos encontrados en el saco dural de cadáveres de recién fallecidos estudiados con diferentes técnicas histológicas. El saco dural espinal está formado por tres estructuras concéntricas: la duramadre, que ocupa el 85-90 por ciento de su espesor, del lado externo; el compartimiento subdural, integrado por células neuroteliales, y la lámina aracnoidea, que ocupa el 5 al 8 por ciento interno. La duramadre, que consta de aproximadamente 80 láminas durales concéntricas, es una estructura permeable y fibrosa, por lo cual posee resistencia mecánica. El compartimiento subdural es una estructura concéntrica, celular, de resistencia mecánica muy baja, donde se pueden producir fisuras concéntricas por rotura de las células neuroteliales dando origen a un espacio subdural adquirido. La lámina aracnoidea es una estructura celular con mayor resistencia mecánica que el compartimiento subdural. Sus células están firmemente unidas por uniones especializadas de membrana y forman una barrera semipermeable que regula el pasaje de sustancias a través del espesor del saco dural. (AU)