[Clinical value of low-frequency repetitive nerve stimulation in myasthenia gravis]

To explore the value of low-frequency repetitive nerve stimulation (RNS) in the diagnosis of myasthenia gravis (MG).

A total of 436 MG patients admitted during the period of July 2008 and August 2010 and undergoing the repetitive nerve stimulation test were reviewed retrospectively. We analyzed the positive rates of RNS in MG patients and compared the abnormalities in different nerves including facial, accessory, axillary and ulnar nerves.

Among them, 73.85% had abnormal recordings on low-frequency RNS test. The highest abnormality was in facial nerves (82.30%), then axillary nerves (52.17%) and the lowest in ulnar nerves (27.64%). The positive rates of RNS in ocular MG were significant lower than those in general MG patients. And there were no significant statistical differences of RNS abnormal rates in types IIa, IIb, III and IV MG patients with 89.66%, 82.56%, 91.67% and 83.33%, respectively. In ocular MG, 16.34% patients were positive in RNS test under the stimulation of accessory, axillary and ulnar nerves. And 79.50% patients with general MG had two or more nerves with abnormal results.

The low-frequency RNS test is of great value in the diagnosis of MG. And it shows a higher sensitivity in general MG patients than that in ocular ones. The stimulation of facial and axillary nerves increases the positive rates of RNS in MG patients.