Muscle and Nerve Histology
Maher Kurdi in 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.
Local Anesthetics and Additives
Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand in Pediatric Regional Anesthesia, 2019
The intraneural diffusion depends upon the structure of the nerve. The different sheaths involved in the packing of nerve fibers are not equivalent as barriers to local anesthetics. The dense structure of the epineurium is usually considered to be the main obstacle to the diffusion of drugs in a nerve trunk, while the perineurium does not represent a significant barrier to the entry of local anesthetics. The structure of the endoneurium varies widely with the age of the patient and with the type of nerve. While being loose and easily traversed (in both directions) in young patients, it becomes progressively enriched in connective fibers in older patients: this may result in increasing the latency of the block and prolonging its duration. The fat content of the endoneurium may be important in some nerves, such as the sciatic nerve, and this may result in nonspecific binding of consistent amounts of the drug (with a subsequent decrease in blocking effects).
Facial Reanimation Surgery
John C Watkinson, Raymond W Clarke, Terry M Jones, Vinidh Paleri, Nicholas White, Tim Woolford in Head & Neck Surgery Plastic Surgery, 2018
Seddon1 described the following types of neuronal injury: Neuropraxia. This is temporary cessation of conduction of the nerve with no loss of axon continuity. Neuropraxia is a transient phenomenon with complete recovery once the causative factor is removed. Axonotmesis. Damage is sustained to the axon resulting in Wallerian degeneration. Regeneration occurs at a rate of 1–4 mm a day and recovery is usually satisfactory.Neurotmesis. The nerve fibre is severed and the endoneurium disrupted. Recovery is unlikely.1, 2
Potential Effects of Stem Cells Derived from the Peripheral Nerve and Adipose Tissue after the Nerve Crush Injury in Control and Obese Rats
Published in Journal of Investigative Surgery, 2022
Elif Kayhan Kustepe, Berrin Zuhal Altunkaynak, Işınsu Alkan, Elfide Gizem Kivrak, Alişan Yildiran, Stefano Geuna
The general view of the peripheral nerve, connective tissue and axonal structures was healthy in the NOC group, and the vessels in the endoneurium were noteworthy (Figures 5 and 6). Myelinated nerve fibers, myelin sheath and unmyelinated axons with mitochondria had a normal appearance (Figure 7). In the NOH group, the peripheral nerve content was seen to be damaged, consisting of axons with scattered boundaries. Also in the endoneurium, macrophages were observed (Figures 5 and 6). Myelinated axons and myelin sheaths had an irregular appearance and scattered myelin sheath fragments were observed. In addition, there were some smaller nerve fibers and thinner myelin sheath in this group when comparing with those of the NOC group. Unmyelinated axons showed less clustering and their number was less than that of myelinated fibers. In Schwann cells, irregular bordered, pycnotic or heterochromatic nuclei were remarkable (Figure 6). Peripheral nerve structures in the NOPS group had a healthy appearance. In this group, small size but thick myelin sheathed axons were observed (Figures 5 and 6). In this group, there was a healthy appearance of Schwann cells (Figure 6). In the histopathological analysis of the NOY group, the density of healthy and small size myelinated and unmyelinated axons observed high (Figures 5 and 6). In addition, degenerate axons, macrophages as well as mast cells have been seen (Figure 5). The endoneurium was healthy and the Schwann cells enveloped more than one unmyelinated axon (Figures 5–7).
Traumatic brachial plexus injury: proposal of an evaluation functional prognostic scoring system
Published in British Journal of Neurosurgery, 2021
Electrophysiology could assist clinicians in determining the prognosis of TBPI. This was usually determined by considering the severity of nerve injury, denervated muscles, and partial or total nerve lesions. The worst functional prognosis was obtained in the initial EMG results in the form of "almost all (≥80%) or all muscles experiencing total denervation". The severity of nerve injury reflected damage that occurred to the supporting structures of the affected nerve (endoneurium, perineurium, and epineurium). When all supporting structures were damaged, axon recovery would be difficult to occur, and as a result, rehabilitation must be assisted with surgical procedures.16 An EMG to evaluate motor function was usually created by looking for intact nerve axons and estimating how severe the axonal damage was. The prognosis worsened with a decrease in the number of motor units found, as well as the absence of spontaneous recovery from potential motor units within 1-9 months.17
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).