| Entrapm ent neuropat hy is a common disease in the clinic.Many complications,such as neuropathic pain,numbness,skeletal muscle atrophy,and motor disability,can result from CNC injury.The current understandi ng of CNC is deri ved from studies invol vi ng anim al models,especially animal models in which the sciatic nerve is banded with silastic tubing.The researchers use the tube models to explore histological and physiological changes of nerve and el ucidate the mechanism of CNC.However,the tubes used for existing models of compression neuropathy are round and uni form i n size,and nerves are obl ate in vi vo and may have di fferent thicknesses in different indi vi duals.Using a uniform inner di ameter silicone tube may cause errors in the experimental results.In addition,the existing anim al models have been used to investigate various post-CNC injury-rel ated changes,such as hypoalgesia,local nerve demyelination or cutaneous neurovascular changes.In clinic,entrapment neuropat hy causes sensory dysfunction,also causes muscle weak ness and wasting in severe chronic nerve compression patients.In nerve compression patients,nerve recovery is rare if muscle atrophy is present for more than one year prior to surgery.Herei n,we propose a new technique for i nducing CNC and expl ore the effect of chronic nerve compression and decompression on muscles with the new CNC model.There are m ainly two parts related on the experiment.Part one: novel model of chronic nerve compressionObjective: to create a new CNC model which can reproduce the pathological changes characteristic of CNC injury in humans.Methods: we use N-butyl-cyanoacrylate(NBCA)and l atex gloves to band the sciatic nerve.At different time points post-operation,we assessed nerve functional changes using the hot plate test and electromyography.Immunofl uorescence and electron microscopic analyses of the nerves were performed to quantify the degree of neuropathological change elicited by the indicated model.In addition,Masson staini ng was perform ed to assess the degree of gastrocnemi us muscle and intrinsic paw muscle fibrosis induced by the model.Results: rats subjected to nerve compression displayed therm al hypoesthesia at 2 weeks after surgery.Nerve conduction velocity(NCV)gradually decreased from 53.4 m/s(before surgery)to 31.5 m/s at 6 months post-operati on.Neuropathological studies dem onstrated that the model caused nerve demyeli nation and axonal irregul arities and triggered collagen deposition in the epineurium and perineuri um of the affected nerve.Furthermore,Masson staining of the gastrocnemius muscle and t he int rinsic muscles of the paws howed that both sets of muscles exhibited increased collagen deposition and morphological changes at 2 months after surgery.Conclusion: the novel m odel can induce functional and histological abnormalities that are reproducible and reliable and is thus a useful CNC model.Part two: Muscle fiber changes in the flexor digitorum longus and lumbrical muscles after nerve compression and decompressionObjective: to explore muscle fiber composition and motor nerve terminal morphology in fl exor digitorum longus and lumbrical muscles after nerve compression and decompression.Methods: we used the new CNC model to assess for changes in the muscles.Rats were randomly separated into four groups: CNC1M(1 month after CNC inj ury),CNC6M(6 months after CNC injury),CNC1M-d(surgical decom pression in CNC1M),CNC6M-d(surgical decompression in CNC6M).The morphology of neurom uscular junctions(NMJs)in the flexor digit orum longus(FDL)and lumbrical muscles,and intra-epidermal nerve fiber density(IENFD)in the footpad were measured.Results: At CNC1 M,the proportions of type I and IIB fibers were decreased,and type IIA and IIX fibers were i ncreased in the lumbrical muscle but no change i n the F DL.There was no change in NMJs morphology in two muscles.The IENFD declined in the CNC footpad.At CNC1M-d,the test returned to norm al.At CNC6 M,the proportions of four muscle fiber types were changed,and t he area of muscle fi bers dec reased in both FDL and lumbrical muscle.Degeneration of NMJs were noted.At CNC6M-d,the changes recovered but failed to return to the normal.Conclusion: These fi ndings woul d be helpful to understand muscle damage and pathphysiological development of the nerve compression,and provide new evidence for early treatment. |
