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Muscle and Nerve Histology
Published in Maher Kurdi, Neuromuscular Pathology Made Easy, 2021
Peripheral nerves develop in the fetus during the 15th week of gestation. Each nerve trunk is divided into multiple fascicles. Each individual fascicle consists of three layers (Figure 1.6): Epineurium, the outer layer, is a dense collagenous connective tissue containing thick elastic fibers.Perineurium, the middle layer, is a cylindrical fibrocollagenous layer containing epithelial membrane antigen (EMA) positively stained perineurial cells. Renault bodies are normal structures with ellipsoid shapes located in the sub-perineurial space. They contain fibroblasts and mast cells and lack of axons. Of 600 sural nerve biopsies, 2% have Renault bodies. Unfamiliarity with these bodies' appearance may result in diagnostic errors. They could be misinterpreted as endoneurial edema or an infarct.Endoneurium, the inner layer, is a loose connective tissue that surrounds individual nerve fiber (axons), fibroblasts, mast cells, fixed macrophages, and capillaries. The endoneurium is completely isolated from the perineurium and Schwann cells.
Diseases of the Peripheral Nerve and Mononeuropathies
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Diana Mnatsakanova, Charles K. Abrams
These include: Endoneurium. This forms the supporting structure around individual axons within each fascicle.Perineurium. Collagenous tissue that encases each fascicle and probably acts as a blood–nerve barrier.Epineurium. Collagen tissue, elastic fibers, and fatty tissue that bind individual fascicles together, providing protection from compression. Merges in the dura mater of the spinal cord.
Microsurgery and Orthopedic Animal Models
Published in Yuehuei H. An, Richard J. Friedman, Animal Models in Orthopaedic Research, 2020
A peripheral nerve is composed of one or more fascicles, covered by an epineurium (Figure 7). Each fascicle is formed by a conglomeration of thousands nerve fibers (axon with surrounding Schwann cell sheath). The connective tissue surrounding the fascicle is called perineurium. A mesoneurium is attached to one side of the nerve trunk for blood supply of the nerve.
Histological and ultrastructural study of AflatoxinB1 induced neurotoxicity in Sciatic nerve of adult male Albino rats
Published in Ultrastructural Pathology, 2020
In the present study, light microscopic examination of semi-thin sections of sciatic nerves of both control and olive oil-treated groups showed the same normal histological architecture. The sciatic nerve was covered from outside by several layers of collagen fibers called epineurium (Figure 2). The connective tissue perineurium appeared as thin layers of collagen fibers containing blood vessels surrounding the nerve fascicles (Figure 1). These contained nerve fascicles were formed of myelinated axons of variable sizes. The axons were surrounded by a dense and thick deeply stained blue myelin sheath. They were separated by connective tissue endoneurium. The axon contained within each myelin sheath appeared pale in staining (Figure 2). Schwann cells exhibited a vesicular nucleus with prominent nucleolus and their cytoplasm stained paler blue than the myelin and could be seen surrounding the myelinated axons and small clusters of non-myelinated axons (Figures 1 and 2).
Distinguishing Benign from Malignant Circumscribed Orbital Tumors in Children
Published in Seminars in Ophthalmology, 2018
Yufei Tu, Frederick A. Jakobiec, Katherine Leung, Suzanne K. Freitag
Typically, schwannomas (Figure 2) of the orbit demonstrate variable but typically hyperintense T2 signal. Variability in T2 signal intensity can be seen, depending on the prevalence of Antoni A or B patterns.1 Tumors that are in the Antoni A group typically demonstrate on MRI uniformly T2 hypointense signaling. Lesions that are in the Antoni B group can exhibit heterogeneous T2 hyperintense signal, with cavitary change.1 Schwannomas are typically avidly enhancing, although areas of cystic/cavitary change can result in regions of heterogeneous enhancement.1,2 No aggressive osseous destruction of the orbital bone is seen on CT. Rather, schwannomas can result in smooth osseous bowing or expansion. In our patient, the schwannoma demonstrated relatively hypointense signaling on T2, isointensity to brain on T2-weighted images, and minimally hyperintensity to skeletal muscle. This would be consistent with the predominant Antoni A growth pattern. The schwannoma also demonstrates no significant restriction of diffusion. Smooth bowing of the lamina papyracea without aggressive erosion is often present on CT. The encapsulation of the tumor by a perineurium is responsible for its elegant circumscription. In an adult, a circumscribed neurofibroma can pose a diagnostic radiographic challenge, but in a child such a lesion is highly exceptional. Most pediatric neurofibromas are of the plexiform and diffuse types.
Peripheral nerve injury and axonotmesis: State of the art and recent advances
Published in Cogent Medicine, 2018
Rui Alvites, Ana Rita Caseiro, Sílvia Santos Pedrosa, Mariana Vieira Branquinho, Giulia Ronchi, Stefano Geuna, Artur S.P. Varejão, Ana Colette Maurício
Each peripheral nerve is covered by three layers consisting essentially of connective tissue and which are histologically called stroma (Mills, 2007). The endoneurium directly coats each axon, and although it contains a thin network of capillaries and microvessels and an outstanding intrinsic elasticity, this layer guarantees little mechanical protection (Mizisin & Weerasuriya, 2011). A group of axons surrounded by endoneurium is called nervous fascicle, and each fascicle is covered by perineurium, a thin but dense connective layer. Stronger than the endoneurium, perineurium provides mechanical protection against tensile forces and supports the blood-nerve barrier and nerve hemostasis, protecting the endoneurial environment against sudden changes of concentration in the vascular and extracellular spaces (Weerasuriya & Mizisin, 2011). All fascicles of a nerve are included within the outermost coating layer, the epineurium, which, depending on the nerve in question and its dimensions, represents between 30% and 70% of the sectional area of the nerve trunk (Rigoard et al., 2009). The inner portion of the epineurium directly coats all fascicles and their perineurial coatings, contains blood vessels that irrigate and travel along the nerve and even small amounts of adipose tissue. The external layer coats the entire nerve, giving it mechanical protection and its anatomical shape (Grinsell & Keating, 2014). While the endoneurium has a longitudinal orientation, the perineurium and the epineurium are circumferentially disposed (Seddighi et al., 2016).