Enhancing diagnostic sensitivity in Myasthenia Gravis: The combined role of CMAP area and amplitude decrements in repetitive nerve stimulation.

OBJECTIVE

To evaluate the diagnostic utility of using CMAP area decrement, in addition to CMAP amplitude decrement, in RNS testing for patients with suspected MG.

METHODS

This retrospective study analyzed EMG data from January 2019 to December 2023 on patients with suspected MG. CMAP area and amplitude decrements of ≥10 % were considered abnormal, and MG diagnosis was based on clinical presentation, antibody testing, or response to treatment.

RESULTS

A total of 204 patients were included in the final analysis. MG was diagnosed in 71 patients (29.8%). The sensitivity of the amplitude decrement was 29.6%, while the sensitivity of the area decrement was 38%, with specificities of 99.2% and 96.12%, respectively. Combining both criteria yielded a sensitivity of 43.7%, representing a 14.1% improvement over amplitude decrement alone.

CONCLUSION

Incorporating CMAP area decrement into RNS testing significantly enhances diagnostic sensitivity for MG, particularly in ocular forms, without compromising specificity. This combined approach presents a promising improvement over existing diagnostic tools for MG, especially in cases where traditional methods have limitations. Future research is needed to validate these findings.

SIGNIFICANCE: This study introduces a practical and easy to adopt enhancement to repetitive nerve stimulation, significantly improving diagnostic sensitivity for Myasthenia Gravis.