Relationship Between Clinical Features And Repetitive Nerve Stimulation In 73 Cases Of Ocular Myasthenia Gravis

Objective: To analyze the repetitive nerve stimulation(RNS)of ocular myasthenia gravis(OMG),investigate the correlation between the clinical characteristics and RNS,and explore the correlation of RNS results with the prognosis of OMG.Methods: Retrospective analysis is conducted on the patients diagnosed as OMG with RNS test in the Department of Neurology of the First Affiliated Hospital of Dalian Medical University from January,2016 to June,2020.Some important clinical data are collected,including the age of onset,gender,initial symptoms,thymoma and thyroid disease,treatment,ocular-quantitative myasthenia gravis score(O-QMGs),acetylcholine receptor antibodies(ACh R-Ab)results,RNS results and nerve stimulation,records of electrode location,decrement in compound muscle action potential(CMAP)amplitude.The last follow-up survey was conducted on all the patients in December2020 to record their outcome and medication status.Result:1.A total of 73 OMG patients are studied,The average age of morbidity was57.75±15.675 years old,including 35 males and 38 females with the male/female(1:1.1);the average age of onset for male is 56.7±16.450,and the average age of onset for female is 58.8±15.079(P>0.05).About 72.6% OMG patients is shown as late-onset(age>50)and about 27.4% OMG patients is shown as early-onset(age≤50).The most common clinical manifestation of OMG was blepharoptosis(54.8%),followed by blepharoptosis combined with diplopia(30.1%).The patients with diplopia were rare(15.1%),Among them,1 suffered from blepharoptosis combined with eyeball fixation.There’s no statistical difference between male and female with regard to the clinical manifestation(P>0.05).Positive rate of ACh R-Ab is 61.8%.Additionally,3 patients were complicated with thymoma and 31.5% patients were complicated with thyroid diseases.2.The positive rate of RNS was 49.3%.The RNS-positive and RNS-negative groups showed no statistical differences in gender,clinical manifestation,ACh R-Ab,thymoma,thyroid diseases,course of disease(P>0.05),but significant differences in O-QMGs and age of onset(early/late)(P<0.01;P<0.05).The positive rate of the facial nerve(orbicularis oculi),axillary nerve(deltoid),accessory nerve(trapezius),radial nerve(anconeus)and ulnar nerve(abductor digiti minimi)was 33.3%,34.4%,28.4%,18.8% and 2.8%,respectively.The positive rate of ulnar nerve is obviously lower than that of other stimulated nerves(P<0.05).Except for the ulnar nerve,there’s no statistical difference between the positive rates of different stimulated nerves in the other two groups.3.The CMAP amplitude decrement of low-frequency repetitive nerve stimulation in facial nerve,axillary nerve,accessory nerve,radial nerve and ulnar nerve is obviously in positive correlation with O-QMGs(P>0.05).The CMAP amplitude decrement of the facial nerve is more obvious in late-onset OMG compared with early-onset OMG(P<0.01).No statistical differences were found in the CMAP amplitude decrement of the facial nerve,axillary nerve,accessory nerve,radial nerve,ulnar nerve at 3 Hz and 5 Hz stimulation(P>0.05).4.Positive radial nerve(OR=10.108,95%CI=1.595-64.067,P=0.014)and immunosuppressive(OR=0.098,95%CI=0.010-0.915,P=0.042)can affect the OMG prognosis.Positive radial nerve has no significant effect on the conversion of OMG patients(P>0.05).Conclusion:1.The male/female ratio of OMG patients is similar.There are more late-onset OMG patients than early-onset;the most common initial clinical feature of OMG is simple ptosis,followed by ptosis with diplopia,but the cases of simple diplopia are relatively rare.2.Axillary nerve shows the highest RNS positive rate,followed by facial nerve,and the ulnar nerve shows the lowest RNS positive rate;OMG with higher O-QMGs show the higher RNS positive rate.It’s discovered that the more severe clinical features,the greater CMAP amplitude decrement of facial nerve,axillary nerve,accessory nerve,radial nerve and ulnar nerve.3.The CMAP amplitude decrement of facial nerve in the late-onset cases is more significant than that of the early-onset cases.4.Positive radial nerve is an independent risk factor for OMG convert to generalized disease,but it has no significant effect on conversion time.Immunosuppressive can reduce the risks of conversion for the OMG patients.