CHARACTERIZATION OF MYASTHENIA GRAVIS USING CLINICAL CLASSIFICATION AND REPETITIVE NERVE STIMULATION

Abstract

Introduction. Nerve stimulation tests are crucial in the early diagnosis and monitoring of neuromuscular disease. The objective of the study was to clinically characterize and validate repetitive nerve stimulation (RNS) testing in patients with the chronic autoimmune neuromuscular disease, myasthenia gravis (MG). Material and methods. Clinical assessment and RNS testing were performed in 30 myasthenic patients. Clinical assessments were classified using the Myasthenia Gravis Foundation of America (MGFA) clinical classification. Results. 30 myasthenic patients were recruited, with a mean age of 48.57 2.4 years and a female/male ratio of 2/1. MGFA classification placed 7 patients in group I (23.3%), 7 in group IIa (23.3%), 7 in group IIb (23.3%), 6 in group IIIa (20%), 2 in group IIIb (6.7%), and 1 in group IVa (3.3%). Additionally, 73.3% of patients had positive acetylcholine receptor (AChR) antibodies, and 20% had been diagnosed with thymoma. The RNS test was positive in 21 patients (70%). Patients with involvement limited to the orbicularis oculi muscles (group I) had a positive RNS test rate of 42.9%, whereas this rate increased to 64.2% in patients where the limbs and truncal muscles were affected (“a” groups: IIa, IIIa, IVa). Where respiratory and pharyngeal muscles were affected (“b” groups: IIb, IIIb), patients had a 100% positive RNS test rate. A statistically significant association was found between RNS test results and AChR antibody levels (p = 0.0041). Conclusions. These findings are of interest for physicians treating MG patients and administering RNS testing and suggest an alternative method for the diagnosis and monitoring of MG, in cases where AChR antibody quantitation is not appropriate.

Keywords

• myasthenia gravis
• repetitive nerve stimulation
• neuromuscular autoimmune disease
• achr antibody.