The Study On The Application Of The Masseter Muscle By Single-Fiber Electromyography In Myasthenia Gravis And Inflammatory Myopathies

Background and Objectives:Single Fiber Electromyography(SFEMG) by means of a special needle electrodes which through the side of its small recording area to identify and record the individual muscle fibers action potential. SFEMG is now widely used clinically as a higher-sensible method of diagnosis, particularly in Identifying of clinical diagnosis of Myasthenia Gravis(Myasthenia Gravis, MG). The objective of this paper is to diagnose significance on the influence of masseter muscle`s SFEMG treatment from MG and inflammatory myopathy, and diagnosis of the results from a series of prospective studies in order to better guide clinical practice. Methods:On the first part of the test, 48 cases completed both SSFEMG and VSFEMG examination during the same time on the same day, there was a break between two examinations which last at least five minutes. Each participant was tested on jitter value and fiber density(FD) value which come from the masseter muscle and the abductor pollicis brevis.On the second part of test, 30 cases of Myasthenia Gravis(MG) patients were admitted to hospital during the same time period on the same day, in property sequence to conduct clinical absolute scores. Masseter low-frequency RNS inspection and SFEMG examination showed that MG group obtained a higher proportion of MCD, the percentage of jitter broadening of potential pairs and blocking potential pairs compared with the control groups.The third part 23 cases of patients with inflammatory myopathy muscle enzymes detection, biceps detection, quadriceps detection, tibialis anterior muscle detection, conventional EMG examination of abductor pollicis brevis, motor and sensory nerve conduction velocity check, masseter single fiber EMG and muscle biopsy. Results:1. The normative value for jitter among Chinese populations are 33μs and 22μs. This result is consistent with similar research result from international researches; the normative values for jitter and FD increased with aging, the jitter and FD value that were obtained from Single Fiber Electromyography(SFEMG) of masseter muscle were not related to gender; jitter and FD value for abductor pollicis brevis were positively correlated with age, however not related to gender; the average normative value for jitter and FD of abductor pollicis are higher than those of the masseter muscle.2. Compare OMG with GMG, OMG patients with age of onset was significantly lower than patients with GMG; the detecting positive rate of GMC is higher than OMG by using RNS method; the overall sensitivity of SFEMG`s diagnostic techniques are 90.0%, which is higher than the 60.0% from RNS. 30 patients with myasthenia gravis treated with cholinesterase inhibitors, hormonotherapy, mycophenolate mofetil(MMF), azathioprine, intravenous immunoglobulin(IVIg), thymectomy, plasma exchange(PE) therapy, then performed QMG test during treatment and as an outcome measure, changes in condition of not-cured group and improved group has no linear relationship with the changes in jitter value, and there is linear relationship between recovery group and effectual group, revealed positive correlation relationship, the greater correlation between recovery group and effectual group, the higher the degree of the condition would improve, the greater correlation between the changes in jitter value and the changes in patients’ condition, jitter value presents a more objective evaluation of the treatment effect in patients who have significant improvement in their conditions.3. The result shows that the biceps, abnormal rate of inserted potential from tibialis anterior, fibrillation potentials, positive sharp waves and the shortening indicator of the mean duration are higher than abductor pollicis brevis; The results also indicates that patients with not associated with interstitial lung disease, their test results of biceps and quadriceps have abnormal rate in fibrillation potentials, positive sharp waves and the shortening indicator of the mean duration are significantly higher compare with those four cases associated with interstitial lung disease; The masseter single fiber EMG test from 23 patients shows abnormality where the muscle fiber density(FD) values are abnormally elevated which accounted for 96%, The abnormal value of jitter is about 78%, which is higher than normal test results, however, a lower rate of anomalistic FD value; analysis and comparison of using single fiber EMG FD values and using serum muscle enzymes to detect the correlation of the CK value indicate the presence of a significant positive correlation between the two. Conclusions:The masseter muscle can be used as an ideal test muscle for Single Fiber Electromyography(SFEMG). Masseter muscle`s jitter value could be more objective to evaluate the treatment effect when Myasthenia Gravis(MG) patient’s` condition significantly improved. During the recovery stage of inflammatory myopathies and when the testing of creatine kinase is normal, SFEMG`s detection ability is even more valuable.