Turns-amplitude analysis and motor unit potential analysis in myasthenia gravis

Objectives - The aims of this study were to investigate myopathic changes i n myasthenia gravis (MG) by using turns-amplitude analysis (TAA) and quanti tative motor unit potential duration analysis (MUPan), to correlate myopath ic changes with severity and duration of the disease and the results of dia gnostic tests including repetitive nerve stimulation test (RNS), single fib er electromyography (SFEMG), and anti-acetylcholine receptor antibody (AChR -ab), and to compare the sensitivities of these two methods in detecting my opathic changes in MG. Materials and methods - We studied both MUPan and TA A in 32 patients with MG. Results - The MUPan study showed myopathic change s in 12 patients (37.5%); TAA revealed a myopathic pattern in 4 (12.5%) and a neurogenic pattern in 4 cases (12.5%). Two of the 4 patients with a myop athic change by TAA also had short-duration mean MUP on the MUPan. No stati stically significant association was found between the myopathic changes ei ther by MUPan or TAA, and the various clinical and laboratory features. Con clusion - We conclude that MUPan is a more sensitive method than TAA in sho wing myopathic changes in MG, and that TAA is of limited help in demonstrat ing them.