Diagnostic Yield and Sensitivity of Repetitive Nerve Stimulation at Different Frequencies in the Evaluation of Myasthenia Gravis

Gaber, Manal M; Korany, Safaa Gamal; Hosny, Hanan; Masoud, Mohammed Mabrouk; Sabry, Reem M

doi:10.21608/ejmr.2025.396295.1847

Diagnostic Yield and Sensitivity of Repetitive Nerve Stimulation at Different Frequencies in the Evaluation of Myasthenia Gravis

Document Type : Original Article

Authors

¹ Department of clinical Neurophysiology, Neuro-Diagnostic and Research Center, Faculty of Medicine, Beni-Suef University, Egypt

² Department of Neurology, Faculty of Medicine, Beni-Suef University, Egypt

10.21608/ejmr.2025.396295.1847

Abstract

Background: Myasthenia gravis (MG) is an autoimmune disorder known by fluctuating muscle weakness due to impaired neuromuscular transmission. A decremental response on repetitive nerve stimulation (RNS) represents the electrical correlate of clinical muscle fatigue and weakness in myasthenic patients. While single-fiber electromyography (SFEMG) remains the most sensitive diagnostic test, it is technically demanding and not always available. RNS is a more accessible tool, though its sensitivity can vary depending on stimulation parameters. Aim: This study aimed to assess the diagnostic sensitivity of high-frequency (10 Hz) RNS compared to the conventional 3 Hz protocol in patients with myasthenia gravis. Methods: A case-control study was conducted on 45 patients with clinically confirmed MG and 45 age and sex-matched healthy controls. Both groups underwent low-frequency (3 Hz) and high-frequency (10 Hz) RNS after withholding anticholinesterase medication for (10-12) hours. Recordings from the abductor digiti minimi, trapezius, and nasalis muscles were analyzed for decremental responses in both amplitude and area. Results: MG patients showed significant decremental responses at both frequencies (p < 0.005). High-frequency RNS demonstrated higher sensitivity in detecting neuromuscular transmission defects, particularly in amplitude and area decrements. Conclusion: High-frequency RNS enhances the detection of neuromuscular transmission abnormalities in myasthenia gravis. Its improved sensitivity and ease of application make it a valuable addition to the diagnostic workup, especially when SFEMG is unavailable or not feasible.

Keywords

Main Subjects

Diagnostic

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