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.
Surgery of the Peripheral Nerve
Timothy W R Briggs, Jonathan Miles, William Aston, Heledd Havard, Daud TS Chou in Operative Orthopaedics, 2020
When nerves have been damaged and surgery has been delayed, a neuroma will have formed. The consistency of a neuroma is important when assessing nerve injury, as a hard neuroma may represent an abundance of connective tissue and little in the way of nerve tissue. Making an incision through the damaged epineurium permits visualisation of any nerve bundles present, and stimulation of the nerve proximally. This may give some indication as to likely recovery. Stimulating the nerve proximally and recording from the nerve distally give the best guide for recovery. An absence of recording distally is a relative indication to resect and repair the nerve, depending on the macroscopic fascicular structure seen. Care should be taken not to undertake excessive mobilisation, as this may lead to devascularisation of a nerve.
Innervation of Fascia
David Lesondak, Angeli Maun Akey in 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.
Microvascular neural blood flow assessment for a chronic nerve compression neuropathy mouse model by fluorescein angiography
Published in Neurological Research, 2022
Shunpei Hama, Takuya Yokoi, Mitsuhiro Okada, Takuya Uemura, Kiyohito Takamatsu, Hiroaki Nakamura
The luminance was significantly lower in the CNC neuropathy groups, and the fluorescein-positive area was also significantly smaller in the CNC neuropathy groups. Histological assessments with Masson’s trichrome staining revealed that the epineural fibrosis areas in the CNC neuropathy groups were significantly larger than that in the control group, and a significant negative correlation was found between the luminance of the compression site and the size of the epineural fibrosis areas of the same site, although the r-value of the present study was relatively low. These findings are consistent with those from a previous study by Mackinnon et al. [2], who found that the fibrosis of the epineurium becomes advanced in CNC neuropathy mice. The epineural fibrosis might affect the delivery of fluorescein to the epineurium and vessels, resulting in the deterioration of the luminance at the site of compression.
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
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).
Related Knowledge Centers
- Nerve Fascicle
- Perineurium
- Spinal Nerve
- Connective Tissue
- Lymphocyte
- Blood Vessel
- Fibroblast
- Nerve
- Spinal Canal
- Intervertebral Foramen