Comparison of the Repetitive Nerve Stimulation Test(RNST) Findings Between in Upper and Lower Extremity Muscles in Myasthenia Gravis / 영남의대학술지

BACKGROUND AND PURPOSE: This study was undertaken to compare the sensitivity of the Repetitive Nerve Stimulation Test (RNST) between the upper and lower extremity muscles in myasthenia gravis(MG) patients. MATERIALS AND METHODS: The study population consisted of 20 normal persons(control group) and 10 MG patients(MG group). Using Stalberg's method. RNST was systemically performed in orbicularis oculi muscle. upper extremity muscles(flexor carpi ulnaris. abductor digiti quinti), and lower extremity muscles(tibialis anterior. extensor digitorum brevis. vastus medialis). RESULTS: There were statistical differences of decremental response(mean+/-SD) in orbicularis oculi and upper extremity muscles between the control and MG groups(p<0.05 or p<0.01). However, there was no statistical difference of decremental response(mean+/-SD) to RNST in lower extremity muscles between the control and MG groups. There were highersensitivity in orbicularis oculi and upper extremity muscles than lower extremity muscles. Although positive reponse were detected in the lower extremity muscles, the positive response rates of lower extremity muscles were lower than o.oculi and upper extremity muscles. CONCLUSIONS: When the response rates of RNST in facial and upper extremity muscles are normal, may not be required RNST in lower extremity muscles.

Comparison of Usefulness of Laboratory Tests in Diagnosis of Myasthenia Gravis / 영남의대학술지

PURPOSE: This study was undertaken to evaluate the clinical usefulness of Tensilon test, repetitive nerve stimulation test(RNST), single fiber EMG(SFEMG) test and acetylcholine receptor antibody(AchR Ab) assay for making diagnosis of myasthenia gravis(MG). METHOD: These tests were performed in 21 MG patients which were classified into 11 ocular, 5 mild generalized, 4 moderate generalized, and 1 chronic severe MG. RESULT: The overall positivity of Tensilon test, SFEMG and AchR Ab was 95%, 87%, and 76% respectively. The overall positivity of RNST was 67%; 38% on flexor carpi ulnaris, 43% on adductor digiti quinti and 62% on orbicularis oculi muscles. The positivity of each test was higher in generalized MG group than in ocular MG group. But we could observe the statistically significant difference only in the RNST(p<0.05). CONCLUSION: Tensilon test showed the highest positivity in all MG groups. So we would like to recommend the Tensilon test for the diagnosis of MG at first, followed by RNST and AchR Ab assay, and SFEMG would be indicated to MG group which showed relatively low postivity in other tests.