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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.
Surgery of the Peripheral Nerve
Published in Timothy W R Briggs, Jonathan Miles, William Aston, Heledd Havard, Daud TS Chou, Operative Orthopaedics, 2020
Ravikiran Shenoy, Gorav Datta, Max Horowitz, Mike Fox
The ends of an injured nerve are cut back progressively until the cut surfaces show bulging healthy nerve bundles. An end-to-end anastomosis is performed, which is possible if the resection gap has been small, little mobilisation of the nerve has been necessary, and the nerve is not under tension. Flexing a nearby joint reduces tension on a nerve, and extra length can be gained by transposition (e.g. anterior transposition of the ulnar nerve) of a nerve. The two principal types of primary repair are epineural repair and fascicular repair. Epineural repair is technically less demanding and faster to complete. Fascicular repair (Figure 5.8) is performed if there has been a clean transection of a nerve trunk (e.g. in the brachial plexus). In each method of repair, the true epineurium is exposed. In a fascicular repair, the matched bundles are opposed and sutured with perineurial 11-0 nylon sutures, and then 10-0 nylon sutures are passed through the perineurium and epineurium. This is done circumferentially to complete the repair. In an epineurial repair (Figure 5.9), the fascicular groups in the nerve ends are matched as closely as possible and the ends are then sutured with 10-0 nylon sutures through the epineurium. An initial suture is placed at each of the lateral ends of the nerve, with interrupted sutures subsequently placed on the anterior and posterior aspect of the nerve to complete the repair.
Innervation of Fascia
Published in David Lesondak, Angeli Maun Akey, Fascia, Function, and Medical Applications, 2020
Most peripheral nerves are enveloped in a three-layer fascial model. Their axons are surrounded by endoneurium, which offers only little mechanical support. Groups of endoneurium-covered axons are then enveloped by a think but dense perineurium, which offers strength in tension, and also maintains the so-called blood–nerve barrier. Finally, the perineurium is again covered by the epineurium, a thick and areolar layer of connective tissue that is highly vascularized and acts as a cushion for the whole nerve bundle. All three fascial layers of the nerve are innervated and contain a thin plexus of potential nociceptors that is likely responsible for some cases of nerve trunk pain. Experiments with rats have shown that inflammation tends to change respective neural axons by making them sensitive to mechanical stimuli.23 Such nerve trunk pain may then appear either as local tenderness of a nerve, or a “doorbell” type of response, where local spot palpation may evoke symptoms in a more distal region.
Neuralgic amyotrophy detected by magnetic resonance neurography: subclinical, bilateral, and multifocal brachial plexus involvement
Published in Neurological Research, 2023
Claudia Cejas, José M. Pastor Rueda, Jairo Hernández Pinzón, Nadia Stefanoff, Fabio Barroso
Multifocal nerve involvement suggests that NA may correspond to a non-systemic vasculitic process of the peripheral nervous system [23]. Since it is self-limited, we did not perform a nerve biopsy to confirm this hypothesis; however, there are reports of cases where biopsy was performed and revealed perivascular inflammation in the epineurium and endoneurium. These histopathologic findings are consistent with probable vasculitic neuropathy [24,25]. We assume that nerve constrictions express different stages of nerve damage since CD8-positive T lymphocytes and thickening of the perineurium at proximal and distal ends of these constriction segments have been described in NA patients [17]. Therefore, types I and II may represent early stages, and types III and IV late stages of nerve injury, ultimately manifesting as constrictions. Although steroids may aid in NA patient recovery, strong evidence in favor of their systematic use is lacking [26]. Nor do we know the implications of subclinical and/or bilateral disease; thus, these findings need to be confirmed.
Differential diagnosis of knee pain following a surgically induced lumbosacral plexus stretch injury. A case report
Published in Physiotherapy Theory and Practice, 2019
William R. VanWye, Harvey W. Wallmann, Elizabeth S. Norris, Karen E. Furgal
Interestingly, peripheral nerve, which is uniquely complex tissue, is the only soft tissue that does not follow the classic physiological phases of healing (Bélanger, 2015). Seddon classified peripheral nerve injury into 3 degrees of injury. The least severe is neurapraxia, followed by axonotmesis, and finally, the most severe form, neurotmesis (Burnett and Zager, 2004). Neurapraxia is a functional injury meaning there is focal demyelination, which is transient in nature. Axonotmesis and neurotmesis are not only functional, but also anatomical, which entails a disruption of nerve continuity (Burnett and Zager, 2004). A neurapraxia can range from 1 day to 3 months with full recovery expected. Axonotmesis has the most variability in recovery time and prognosis. Sunderland further divides axonotmesis into three classifications (i.e. Sunderland II–IV). In Sunderland II axonotmesis, the axon is injured, but the endoneurial tube is normal. This generally results in full recovery in 1–6 months. In Sunderland III axonotmesis, the endoneurial tube is injured; in this case, the recovery is less certain with partial return expected in 12–24 months. Lastly, with the Sunderland IV axonotmesis, only the epineurium is intact (i.e. the outer layer of the nerve) and recovery requires surgical intervention. Neurotmesis is a loss of nerve continuity, requiring surgical intervention with unpredictable recovery (Goubier and Teboul, 2015). Considering the patient’s steady progress and full recovery, the stretch injury appeared to be consistent with either a neurapraxia or Sunderland II axonotmesis.
Ozone Partially Decreases Axonal and Myelin Damage in an Experimental Sciatic Nerve Injury Model
Published in Journal of Investigative Surgery, 2019
Zahir Kızılay, Nesibe Kahraman Çetin, Mehran Aksel, Burçin İrem Abas, Serdar Aktaş, Haydar Ali Erken, Abdullah Topçu, Ali Yılmaz, Cigdem Yenisey
TheFIGURE 3epineurium (a thick fibrous connective tissue) and perineurium (a thinner connective tissue of nerve fascicles) were seen, respectively, from outside to inside in the light microscopic examination of the sections obtained by staining the sciatic nerves with hematoxylin-eosin and toluidine blue in rats of the C and O intact groups. Schwann cells, which envelop axons, were distinguished by their oval or round nuclei under the endoneurium. Axons were observed to be faded in color in the cytoplasm of Schwann cells. The presence of a myelin sheath, which is made by Schwann cells and wraps around the axon, was seen in myelinated nerve fibers. Unmyelinated nerve fibers, connective tissue cells, and blood vessels were distinguished among the myelinated nerve fibers (Figure 3A–D).