The Value Of Auxiliary Examination In The Diagnosis Of Ocular Myasthenia Gravis

Objective: The aim of the study is to explore the role and clinical value of the commonly used auxiliary examination,serum antibody detection and electrophysio-logical examination in the diagnosis of ocular myasthenia gravis.Material and Method: Retrospective analysis of 68 cases of diagnosis and treatment of ocular myasthenia gravis cases in Shangrao people's hospital and other hospitals from January 2013 to January 2018.We collected the patient's age,sex,symptoms to diagnosis the average time(years),starting symptoms(ptosis,diplopia,ptosis and diplopia),acetylcholine receptor(AChR antibody,muscle specific kinase(MuSK)antibody,low-frequency repetitive nerve stimulation(RNS),single-fiber electromyography(SFEMG),needle electromyography(NEMG)and other clinical and auxiliary examination materials.The sensitivity and specificity of AChR antibody,MuSK antibody,low-frequency RNS,SFEMG and NEMG in OMG patient diagnosis were compared,and the risk of OMG to GMG transformation by AChR antibody,MuSK antibody,low-frequency RNS,SFEMG and NEMG examination during the 2-year follow-up period was analyzed.The aim of the study is to understand the diagnostic value and prognostic value of AChR antibody,MuSK antibody,lowfrequency RNS,SFEMG and NEMG examination on OMG.Results: 1.Among the 100 patients with newly developed blepharoptosis and/or diplopia diagnosed and treated in the outpatient or ward of Shangrao people's hospital and other hospitals at various levels from January 2013 to January 2018,68 patients with OMG were aged 20-73 years old,among whom 55.8% were males,38 were females and 30 were females.The average time from symptom onset to diagnosis was 1.2±1.3 years,and the diagnosis time ranged from 1 month to 5 years;2.All OMG patients were tested with AChR antibody and MuSK antibody,while 32 patients in the control group were tested with AChR antibody and 20 patients were tested with MuSK antibody.The sensitivity and specificity of AChR antibody were54.41% and 94.87% on OMG patients.Among 68 OMG patients,10(14.71%)were positive for MuSK antibody,and the sensitivity of MuSK antibody was 14.71%.Inthe control group,only one patient of 20 patients in the control group were positive and 19 were negative for MuSK antibody,with specificity of 95%;3.All sixty-eight OMG patients underwent thymic CT and/or MRI,and thymic hyperplasia/thymoma rate was 66.18%.In the control group,sixteen patients underwent thymic imaging examination,among which one patient had thymic hyperplasia and fifteen patients had normal thymus.Among them,81.08% of OMG patients with AChR antibody positive had thymic hyperplasia/thymoma,and 18.92% had normal thymus.Of the ten OMG patients with positive MuSK antibody,only one patient(10%)had thymic hyperplasia;4.All sixty-eight OMG patients underwent low-frequency RNS and SFEMG examinations,and twenty patients in the control group underwent this examination.NEMG examination was performed in twenty-two OMG patients.The sensitivity and specificity of low frequency RNS to OMG was 63.24% and 95.00%respectively.The sensitivity of SFEMG was 95.59%,which was significantly higher than that of RNS(P<0.05).The specificity of SFEMG was 85.00%,and there was no statistical difference between SFEMG and RNS.Compared with the low-frequency RNS,the NEMG sensitivity was significantly reduced,with only 9.09%,which had significant statistical significance(P<0.05),and the specificity was 100.00%(P >0.05),with no statistical difference;5.We compared the frequency of transformation from OMG to generalized myasthenia gravis(GMG)in different test groups.The systemic conversion rate of AChR antibody positive patients was37.84% within 2 years,and that of AChR antibody negative patients was 12.90%.The systemic conversion rate of AChR antibody positive patients was significantly higher,which was statistically significant(P<0.05).The systemic conversion rate of patients with positive MuSK antibody was 50.00%,which was higher than patients with negative antibody(22.41%),however,it was not statistically significant(P>0.05).The whole conversion rate of AChR antibody /MuSK antibody positive patients was 37.21%,which was significantly higher than that of negative patients(8.00%),with significant statistical significance(P<0.05).During the 2-year follow-up period,30.23% of OMG patients with low frequency RNS positive were converted to GMG,while 20.00% of OMG patients with low frequency RNS negative were converted to GMG within 2 years.The conversion rate of OMGpatients with low frequency RNS positive was higher,but there was no statistical difference(P>0.05).28.33% abnormal OMG patients with SFEMG were converted to GMG within 2 years,while 12.50% normal OMG patients with SFEMG were converted to GMG within 2 years.There was no statistical difference between the two(P>0.05).Conclusion:1.The proportion of male and female patients with OMG is similar to MG,and female patients are more than male patients;2.The positive rate of AChR antibody in OMG patients was 54.41%,while the positive rate of MuSK antibody was 14.71%.The incidence of thymic hyperplasia/thymoma in AChR antibody positive patients was significantly higher than that of MuSK,and basically no thymic lesions in OMG patients with MuSK antibody positive;3.The sensitivity of SFEMG in the electrophysiological examination of OMG patients was the highest,followed by the low-frequency RNS and the lowest is NEMG;4.Positive AChR antibody may serve as a risk predictor for OMG to GMG conversion,while low-frequency RNS and SFEMG cannot predict its risk.