Jitter analysis with concentric needle electrodes in the extensor digitorum communis for the diagnosis of myasthenia gravis: a pilot study.

BACKGROUND

Single-fiber electromyography is the most sensitive neurophysiological test for the diagnosis of myasthenia gravis (MG), but its use is limited by the potential risk of transmission of infections. Jitter analysis with disposable concentric needle electrodes (CNEs) is therefore being investigated. This pilot study aimed to evaluate jitter analysis with CNEs for the diagnosis of MG.

METHODS

Forty-two healthy Chinese volunteers and 44 MG patients were prospectively enrolled. MG patients were classified according to the Osserman classification, and acetylcholine receptor antibody titer was measured. Jitter analysis with CNEs in the extensor digitorum communis and repetitive nerve stimulation (RNS) testing were performed. Jitter was expressed as the mean consecutive difference (MCD), and 20 action potential pairs were analyzed in each subject. The mean MCD in each subject and the mean individual MCD of all action potential pairs were compared between groups.

RESULTS

The mean MCD and mean individual MCD were higher in MG patients ((42.3 ± 20.0) µs and (42.2 ± 26.0) µs) than in healthy volunteers ((23.0 ± 3.1) µs and (22.8 ± 7.5) µs). The area under the receiver operating characteristic curve for the mean MCD of MG patients and healthy volunteers combined was 0.85. The mean MCD and mean individual MCD were higher in generalized MG patients ((64.1 ± 18.5) µs and (63.6 ± 30.0) µs) than in ocular MG patients ((33.1 ± 12.0) µs and (33.2 ± 17.6) µs), and were higher in MG patients with abnormal RNS results ((57.2 ± 18.3) µs and (57.3 ± 29.2) µs) than in MG patients with normal RNS results ((32.9 ± 14.8) µs and (32.7 ± 18.3) µs). Abnormal RNS results were observed in 38.60% (17/44) of MG patients and abnormal jitter were observed in 72.70% (32/44) of MG patients.

CONCLUSION

Jitter analysis with CNEs is feasible for the diagnosis of MG.