Clinical and Electrophysiological Markers in Myasthenia Gravis Patients.

OBJECTIVE

We investigated the correlation between disease severity and electrophysiological characteristics in 77 Chinese myasthenia gravis (MG) patients.

MATERIALS AND

METHODS

Disease severity was assessed and compared with repetitive nerve stimulation (RNS) and needle electrode electromyography (NEMG) evaluations.

RESULTS

The quantified myasthenia gravis (QMG) and MG-activities of daily living (MG-ADL) scores correlated well with the proximal muscle decremental response rate. NEMG revealed that 22 patients (28.6%) had myopathic changes, but none demonstrated spontaneous potentials. Only motor unit potentials showed short durations and low amplitude changes. Patients with myopathic changes had higher QMG and MG-ADL scores, and their classifications were different from patients with normal NEMG results.

CONCLUSIONS

Decreased RNS compound muscle action potential amplitudes correlated with MG severity, and were more pronounced in the proximal than in the distal muscles. Patients with myopathic changes showed more severe disease characteristics. Thus, electrophysiological tests are useful for MG diagnosis and can indicate disease severity.