Biomedical subjects

M A Reina

Publications and source records attributed to M A Reina.

25 records · Page 2Linked to original sources

PubMed1996

[Structural analysis of the thickness of human dura mater with scanning electron microscopy].

INTRODUCTION: The only references to the thickness of the human dura mater, reporting its size at various levels, are now 50 years old. Our aim was to study its tridimensional structure with the aid of the scanning electron microscope. METHOD: The samples, which were taken 8-12 h after death from 4 human cadavers between 70 and 78 years old, were examined on 2 orthogonal planes (radial longitudinal and transversal). RESULTS: The architectural structure of the external membrane of the meninges was unusual. The dura mater is made up of elastic collagen fibers organized in successive parallel planes on the surface of the medulla. Each plane constitutes a unit which we will call a sub-laminae. The sub-laminae are found in groups of 8 to 12 that form larger units called laminae, which are between 4 and 5 microns thick. The full thickness of the dura mater at the level of the third lumbar vertebrate contains from 78 to 82 laminae which together measure 270 microns. CONCLUSION: The dura mater is made up of a large number of sublaminae that are concentrically parallel to the surface of the medulla. The fibers in general run in all directions and are oriented differently in each sub-lamina. The orientation of fibers that can be seen on the outer or epidural surface corresponds only to the fibers of the outermost lamina, which has a thickness of 78 to 82 microns. A needle that pierces the dura mater passes through some 700 to 800 sublaminae, each with its own particular distribution of fibers.

Aged↗

PubMed1996

[Iatrogenic spinal epidermoid tumors. A late complication of spinal puncture].

INTRODUCTION. Epidermoid tumors in the spinal canal are rare. Whether congenitally or iatrogenically caused, they form as the result of epidermal cells implanted within the spinal channel. Such implantation can occur during a variety of procedures and events such as bullet wounds, surgery, myelography or punctures for diagnosis, anesthesia or treatment. Although this complication is not discussed in books or journals on anesthesiology, we have found it mentioned in over 100 published cases reporting iatrogenically caused spinal epidermoid tumors. ETIOPATHOGENESIS. Iatrogenic epidermoid tumors of the spine derive from the implantation of epidermal tissue transported inside the spinal canal during lumbar punctures without guidance or with inadequate guidance. There is ample evidence that such tumors are iatrogenic. All cases occur in patients with a history of lumbar puncture. They are rarely associated with congenital anomalies. They are extramedullary. They tend to develop near sites of earlier lumbar puncture, usually near the conus medullaris and the cauda equina. Iatrogenic epidermoid tumors of the spine have been reproduced experimentally in two studies in which autologous skin fragments were implanted in the spinal canal. CLINICAL SIGNS. These tumors are well tolerated by patients for extended periods of time, ranging from 2 to 10 years. At the cauda equinus, tumors can grow slowly for long periods without signs of nerve compression. Symptoms are directly related to tumor size and site. All patients with tumors at the cauda equinus report severe pain radiating toward the roots of compressed nerves. Nuclear magnetic resonance makes it possible to detect the tumor without administration of intrathecal contrast. At present gadolinium-DTPA improves the image so that these tumors can be distinguished from other types. The prognosis for epidermoid tumors of the spine is good, as they are histologically benign. Treatment is always surgical. CONCLUSION. Although the causal relation between epidermoid spinal tumors and lumbar puncture is well documented, anesthesiologists are not sufficiently aware of this possible complication. Between 1977 and 1995, 28 new cases were published. We believe that a deeper understanding of such rare complications will show us how to prevent them while providing appropriate use of epidural and subarachnoid anesthesia.

Epidermal Cyst↗

PubMed1995

[Skin fragments carried by spinal needles in cadavers].

Epidural or intradural puncture with inappropriately stiffened or improperly placed needles can carry cells or fragments of epithelial tissue into the epidural or intradural space. These skin fragments feed by imbibition, possibly leading to the development of epidermoid cysts. We aimed to study the ability of today's needles to transport cells or epithelial fragments. We studied 120 needles in 6 groups of 20, as follows: group 1, Touhy G-16; group 2, Touhy G-17; group 3, Quincke G-22; group 4, Quincke G-26; group 5, Sprotte G-22, and group 6, Sprotte G-24. These needles were used to make intradural and epidural insertions, as indicated, with stiffeners fully in place. Insertions were made into 3 cadavers, epidermal cells or skin fragments were then isolated from the solutions used to wash the needles, and the samples were studied under an optical microscope. We identified groups of cells or epidermal tissues in 45% of the Touhy G-16 samples and in 30% of the Touhy G-17 samples. Squamous epithelial cells were found in 15% of the Quincke G-22 samples and in 30% of the Sprotte G-22 samples. There was a significant difference between the amount of tissue transported by the Touhy needles in comparison with the Quincke (p < 0.01) and Sprotte (p < 0.05) needles. Needles from some manufacturers transport epithelial fragments during lumbar puncture. We believe that better quality control during manufacture of epidural and intradural needles can help to eradicate the rare neurological complications derived from the removal of epithelial cells and their subsequent deposit inside the spinal channel.

Cadaver↗

PubMedDate not supplied

New perspectives in the microscopic structure of human dura mater in the dorsolumbar region.

BACKGROUND AND OBJECTIVES: The object of this study was to describe the three-dimensional structure of the dura mater by use of scanning electron microscopy. METHODS: Microscopic dissection of the dura mater from four fresh cadavers (aged 70, 75, 76, and 80 years) 8-12 hours after death were investigated in three different planes (longitudinal, tangential, and transverse). RESULTS: The external surface of the dura mater, facing the epidural space, consisted of a network of randomly oriented fine collagen fibers. The thicker elastic fibers (2 microns in diameter) were observed on the surface of the dura. In the inner part of the dura mater, there were very fine lamellae of collagen fibers, which were bundled into thicker (4-5 microns) layers. The dura mater consisted of 78-82 layers, each layer including 8-12 very fine lamellae. CONCLUSIONS: The fibers of the dura mater do not run in a longitudinal direction and are not arranged in a parallel fashion. Cytoarchitecturally the dura mater is a laminated structure built up from well-defined layers oriented concentrically around the medulla spinalis.

Aged↗

PubMedDate not supplied

An in vitro study of dural lesions produced by 25-gauge Quincke and Whitacre needles evaluated by scanning electron microscopy.

BACKGROUND AND OBJECTIVES: A study using scanning electron microscopy showed that although the laminas forming the dura mater are concentric and parallel to the surface of the medulla, the fiber layers' orientations are different in each sub-lamina, dispelling the conventional knowledge that all the fibers of the dura are arranged in a parallel direction. Thus, this study evaluated the dural lesions produced by Whitacre and Quincke spinal needles in the external and internal surface of the dura mater of the lower spine area in an attempt to gain more insight into the pathophysiology of postdural puncture headaches (PDPH). METHODS: The T11-L4 dural membranes from 5 fresh (immediately after extraction of organs for transplantation), male patients declared brain dead, ages 23, 46, 48, 55, and 60 years, were excised by anterior laminectomy. Morphologic orientation of the membrane and normal pH were maintained with an apparatus designed for this purpose. One hundred punctures (20 on each sample) at 90-degree angles were done with a new needle each time, 50 with 25-gauge Whitacre and 50 with 25-gauge Quincke needles. Half of the punctures with the Quincke needles were done with the bevel in parallel direction to the axis of the spinal cord, and the rest with the bevel perpendicular to it. Fixation in solutions of 2.5% glutaraldehyde phosphate buffer, followed by dehydration with acetone, was done 15 minutes after the punctures. After acetone was removed at ideal conditions of temperature and pressure, the specimens were then metallized with carbon followed by gold and inspected under a scanning electron microscope. RESULTS: Twenty-five of the Whitacre and 23 of the Quincke punctures were found for evaluation. There were no differences in the cross-sectional area of the punctures produced by the Whitacre or Quincke needles on the dura. The area of the dural lesions produced by 25-gauge Quincke needles, 15 minutes after they have been withdrawn, was 0.023 mm2 (confidence interval [CI] 95%, 0.015 to 0.027) in the external aspect (epidural surface) and 0.034 mm2 (CI 95%, 0.018 to 0.051) in the internal aspect (arachnoid surface) of the dural sac. The area of the lesions produced by the 25-gauge Whitacre needles was 0.026 mm2 (CI 95%, 0.019 to 0.032) and 0.030 mm2 (CI 95%, 0.025 to 0.036) in the external and internal surfaces of the dural sac, respectively. There were no significant differences in the cross-sectional areas of the punctures produced by the 25-gauge Whitacre or 25-gauge Quincke needles. Moreover, with Quincke needles the dural lesions closed in an 88.3% (CI 95%, 86.3 to 92.4) and 82.7% (CI 95%, 74.1 to 90.9) of their original sizes in the epidural and arachnoid surfaces, respectively. With Whitacre needles, the closure occurred in an 86.8% (CI 95%, 83.8 to 90.3) and 84.8% (CI 95% 81.7 to 87.3) in the dural and arachnoid surfaces, respectively. However, there were differences in the morphology of the lesions. The Whitacre needles produced coarse lesions with significant destruction in the dura's fibers while the Quincke needles produced a 'U'-shaped lesion (flap) that mimics the opened lid of a tin can, regardless of the tip's direction. CONCLUSIONS: The needles produced lesions in the dura with different morphology and characteristics. Lesions with the Quincke needles resulted in a clean-cut opening in the dural membrane while the Whitacre needle produced a more traumatic opening with tearing and severe disruption of the collagen fibers. Thus, we hypothesized that the lower incidence of PDPH seen with the Whitacre needles may be explained, in part, by the inflammatory reaction produced by the tearing of the collagen fibers after dural penetration. This inflammatory reaction may result in a significant edema which may act as a plug limiting the leakage of cerebrospinal fluid.

Adult↗

PubMedDate not supplied

[Possibility of nerve lesions related to peripheral nerve blocks. A study of the human sciatic nerve using different needles].

UNLABELLED: When a needle tip comes too close to a nerve axon, the mechanical effect over the nerve membrane produces paresthesia. We examined the hypothetical mechanical damage of short bevel and long bevel needles over sciatic nerve bundles under scanning electron microscopy. METHODS: We obtained samples of sciatic nerve from three patients of 68, 74 and 76 years old. These samples were fixed, dehydrated and coated with gold microfilm for their observation under scanning electron microscopy. Ten short bevel needles and ten long bevel needles were studied under the same microscopic technique. We interpolated microscopic images from sciatic nerve samples and different needle bevels at various angles to study the mechanical damage of these needles to nerve axons. RESULTS: Sciatic nerve bundles were found 0.1 to 0.2 mm deep in the samples; information was given about the bevel length and angle of needles. The damage is perceptible under scanning electron microscopy, when the needle bevel is introduced 0.3-0.4 mm deep into the nerve bundle; here, the needle tip cuts through the perineurum, piercing the nerve bundle. At a depth of 1 mm, the lesion caused by short bevel needles is greater than that caused by long bevel needles. The type of epineural lesions caused by short bevel needles is also different from the ones caused by long bevel needles. CONCLUSIONS: Lesions that affect superficially the epineurum can cause paresthesia by compression of nerve fascicles without damaging the axons. If the perineurm is damaged, the lession will also affect the blood-nerve barrier, leading probably to posterior sequels.

Aged↗

PubMedDate not supplied

[Characteristics and distribution of normal human epidural fat].

Epidural fat provides sufficient cushion for the pulsatile movements of the dural sac, protects nerve structures, facilitates the movement of the dural sac over the periosteum of the spinal column during flexion and extension, and forms a pharmacologic reservoir of lipophilic substances. We review epidural fat and related structures, including their development during the fetal period when the epidural space is filled by undifferentiated loose, areolar mesenchymal tissue that surrounds the dural sac. In the adult, epidural fat has a continuous distribution and follows a certain metameric pattern. It is located mainly on the dorsal side of the epidural space, where it is organized in triangular capsules joined to the midline of the ligamentum flavum by a vascular pedicle. We consider the distribution of epidural fat in the axial and sagittal planes; its presence in the anterior, lateral and posterior epidural space; its presence in the cervical, thoracic and lumbar portions of the spinal column; and its characteristics and variations according to differing body habits and sex. Finally, we speculate on the possible anesthetic implications of epidural fat in terms of the pharmacokinetics of drugs injected into the epidural space and the tasks of locating the epidural space and inserting an epidural catheter during anesthetic procedures.

Adipocytes↗