João Aris Kouyoumdjian1, Erik Stålberg. 1. Department of Neurological Sciences, Neuromuscular Investigation Laboratory, São Paulo SP, Brazil. jaris@terra.com.br
Abstract
OBJECTIVE: To estimate jitter parameters in myasthenia gravis in stimulated frontalis and extensor digitorum muscles using the concentric needle electrode. METHODS: Forty-two confirmed myasthenia gravis patients, being 22 males (aged 45.6±17.2 years-old) were studied. Jitter was expressed as the mean consecutive difference (MCD). RESULTS: MCD in extensor digitorum was 61.6 µs (abnormal in 85.7%) and in frontalis 57.3 µs (abnormal in 88.1%). Outliers represented 90.5% for extensor digitorum and 88.1% for frontalis. At least one jitter parameter was abnormal in 90.5% of the combined studies. Acetylcholine receptor antibody was abnormal in 85.7% of the cases. CONCLUSIONS: Stimulated jitter recordings measured from muscles using concentric needle electrode can be used for myasthenia gravis diagnosis with high sensitivity. Extensive normative studies are still lacking and, therefore, borderline findings should be judged with great caution.
OBJECTIVE: To estimate jitter parameters in myasthenia gravis in stimulated frontalis and extensor digitorum muscles using the concentric needle electrode. METHODS: Forty-two confirmed myasthenia gravispatients, being 22 males (aged 45.6±17.2 years-old) were studied. Jitter was expressed as the mean consecutive difference (MCD). RESULTS:MCD in extensor digitorum was 61.6 µs (abnormal in 85.7%) and in frontalis 57.3 µs (abnormal in 88.1%). Outliers represented 90.5% for extensor digitorum and 88.1% for frontalis. At least one jitter parameter was abnormal in 90.5% of the combined studies. Acetylcholine receptor antibody was abnormal in 85.7% of the cases. CONCLUSIONS: Stimulated jitter recordings measured from muscles using concentric needle electrode can be used for myasthenia gravis diagnosis with high sensitivity. Extensive normative studies are still lacking and, therefore, borderline findings should be judged with great caution.