Radiation-induced Peripheral Nervous Injury: Report 21 Cases

Objective: To discuss the pathogenesis, clinicalcharacteristics, treatment and prognosis on Radiation-inducedperipheral nervous injury.Methods: Neurolysis (4 cases), reconstruction of lumbricalmuscle function (1 cases) and nonsurgical treatment (16 cases)were carried out.Results: All of the 21 cases' clinical symptoms gotaggravated rather than relieved.Discussion: Radiation-induced peripheral nervous injuryoften occurs after radiotherapy. With no feasible way to cure thedisease, it remains a tough nut to crack in the medical world.Along with the progress of aggressive tumor diagnosis andradiotherapy, and prolonged patient's life span, diseaseincidence increases rapidly.Pathogenesis: The pathogenesis of disease is indefinite,probably related to the following reasons.Specialists view it as related to that of the indirect injury ofradiation. Radiotherapy can result in the degeneration ofadipose tissue and fibrous tissue of circum brachial plexus,inter-nerve tract and endo-nerve tract. gradually formingscarring and fibrosis Hence, neurofibra are extensivelystrangled, and nerve-tract crushed, microcirculation ofecto-nerve and intra-nerve damaged. Radiation can alsodirectly damage blood vessel that supply nutrition to nerve,cause vascular endothelial cell proliferation, and vessel wallscarring and fibrosis resulting in blood circulation disorder,especially that of vascular occlusion, until ischemia of neuriteand myelin sheath occur. Regional ischemia and hypoxia canlead to acidosis, and hence produce more oxyradical to affectenzyme system and cell metabolism, which, in turn, destroysbiomembrane, induces cell and mitochondrion edema, andenergy's dysbolism, and inhibits protein synthesis. Whenlysosom gets affected, it releases proteinase, lyzes tissues andcells ,and even hinder the metabolizability of arachidonic acid.Thus, prostacyclin's synthesis decreases resulting indisequilibrium of ratio's prostacyclin and thromboxane A2,which leads to thrombocyte aggregation and vasoconstriction ,hypercoagulabale state of blood, further damage onmicrocirculation, and the final nerve's ischemia and hypoxiainfernal circle. A successive situation like this will lead to astrangulated ischemia state of nerve, and disordered nerveconduction. Some argue for the interaction of thepathogenesisoa disease and a directly injury of nerve byradiation,i.e.radiation can cause edema of ecto-nerve andintra-nerve, and accrementition of fibrous tissue, andInflammatory reaction of nerve. Others presume a factor fromoperation. For example, radical correction of breast cancer candestroy blood circulation of rachial-nerve, and thus causedegression of nerve compliance. Also, individual difference ofradio-vulnerability should not be overlooked. With identicalradiation method and dose, different clinical manifestationsappear on different individuals at skin and hypoderma.Difference of Radiosensitiveness between individuals is aninternal agent, while increase of radiation dosage, utilization ofhigh energy ray, and overlapping of radiation's irradiatedregions are some of the external factors. Investigation provesthat higher dose of radiation fractionated or/ and greater totaldose most probably cause grave advanced stage radiationinjury. Incubation period of radiation brachial plexus often getsshortened, more severe symptom tends to occur, andprognosis turns perishing, when radiation dose is increased.More high energy ray applied, can induce maxlmum dosedistrict's movements from epidermis to dermis, covering up thefact of tissue damage induced by large dose, and thus, easilyleading to radiation-induced peripheral nerve injury. Cheng andSchulz [16] found that extensive connective tissue fibrosis andassociated peripheral nerve injury occur earlier (a few monthsto a few years compared with many years) and/or at lowerradiation doses (5000 to 6000 cG compared with 8000 to 10000 cGy or more) when the peripheral nerve is situated in ornear tissue subjected to dissection before radiation therapy.Clinical diagnosis: The patient have a confirmativeradiotherapy history and a asymptomatic intermission ofmonths to years, and there is a slow,gradually aggravatesensorimotor disorder, severe pain, functional innervation areadisorder, and even incapacitation. Under CT, MRI, PET andother auxiliary examination, and by excluding other diseasesuch as relapse and metastasis of tumor, such a case can bediagnosed.Treatment and prognosis:Conservative treatment failedto circumscribe the development of the disease. Operationalsolution failed to relieve clinical symptom. Prophase of thiscase of patient may benefit from the method of operationalsolution or any kind of tissue's transplantatio, including muscleand greater omentum etc, to cover and wrap up nerve. But themethod couldn't afford any curative effect to sensory functionand motor function, and probably aggravate their clinicalsymptom of sensory and motor function. Other treatment,including occupational therapy and physical therapy etc, can'tafford complete healing as well, while can only contribute torelieving patient's mental stress and to sufficiently using oflimbs' remanent action. Hormone treatment can temporaryrelieve symptom, rather than cure the disease at essence, andcan easily lead to severe complication afterwards. Fibrolysistreatment, in which HAase is used as lytic agent to lyzeredundant Ecto-Cell Matrix (ECM) and GAC at nerve exteriorand interior [40], often helps to strike a new dynamic balance, toadjust cell metabolism internal environment, to relieveconglutination and entrapment at nerve exterior and interior, tolower axon's pressure, and to create good conditions fornerve's regeneration and recovery. Due to the limited casesinvolving such a treatment, retrospective investigation is hencemade impossible to arrive at any precise curative effectevaluation.Conclusion:Radiation-induced peripheral nervous injuryis a kind of tardy, gradual and nonreversible injury of peripheralnerve with no effective treatment witnessed up-to-date.Precaution plays an important role in combating thedisease .The patient who had gone through radiotherapyshould recheck regularly at special out-patient clinic to avoidmissed diagnosis and misdiagnosis. Any case concernedshould be spot in time with a suitable treatment prepared. It isalways necessary to probe into the mechanism ofradiation-induced brachial plexopathy to find out an effectiveway to treat the disease.