ID 376 – Concentric needle jitter in 57 myasthenia gravis patients

Abstract

Objective To estimate the jitter parameters in confirmed myasthenia gravis (MG) in stimulated Extensor Digitorum (ED) and Frontalis (FR) using concentric needle electrode (CNE). Methods 57 MG patients, 31 male, mean age 47.7 ± 16.6 years, 10 ocular and 47 generalized, were studied. Jitter was expressed as the mean consecutive difference (MCD). Upper limit of normality (ED and FR) was set to 24 and 21 μs for mean MCD and 35 and 28 μs for individual MCD values. Acetylcholine receptor antibody (AChRAb) was measured together with the jitter studies. Repetitive nerve stimulation (RNS) results were taken from the patients file. Results Mean MCD (ED and FR) was abnormal in 89.4% and 91.5% (generalized) and 70% and 60% (ocular). Percentage of outliers (ED and FR) was abnormal in 89.4% and 91.5% (generalized) and 50% and 70% (ocular). Some jitter parameters were abnormal in 91.5% (generalized) and 80% (ocular). AChRAb was abnormal in 91.5% (generalized, mean 10.96 nmol/L) and in 60% (ocular, mean 2.75 nmol/L). RNS in different hand, arm and facial muscles was abnormal in 93.5% (generalized) and 40% (ocular). Conclusions Stimulated jitter recordings measured from CNE can be used for MG diagnosis with a high sensitivity, mainly for ocular form.