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A Comparison of Electrodiagnostic Tests in Ocular Myasthenia Gravis

Katzberg, Hans D BSc, MD; Bril, Vera MD, FRCP(C)

Journal of Clinical Neuromuscular Disease: March 2005 - Volume 6 - Issue 3 - p 109-113
doi: 10.1097/01.cnd.0000155026.66153.f0
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Objectives: We aimed to determine whether the diagnostic yield of single-fiber electromyography (SFEMG) in different grades of ocular myasthenia gravis (OMG) is enhanced by repetitive nerve stimulation studies (RNS).

Methods: One hundred twenty-one patients with a diagnosis of mild, moderate, or severe OMG based on clinical criteria had SFEMG of the frontalis muscle and RNS of the facial nerve. Tests results were compared by contingency table analysis.

Results: In these patients, 19% had abnormal RNS and 95% had abnormal SFEMG. SFEMG was abnormal in 93%, 96%, and 100% with mild, moderate, and severe OMG, respectively. One patient with abnormal RNS had normal SFEMG, but the SFEMG study was incomplete.

Conclusion: Like in generalized MG, SFEMG is more sensitive than RNS for all grades of OMG. Furthermore, if a complete SFEMG study is normal, addition of RNS does not improve the diagnostic yield.

From the Division of Neurology, Department of Medicine, University Health Network and University of Toronto, Toronto, Ontario, Canada.

Received for publication April 12, 2004; revised September 4, 2004; accepted December 15, 2004.

Reprints: Vera Bril, Division of Neurology, EN-11-209, Toronto General Hospital, UHN, 200 Elizabeth Street, Toronto, ON M5G 2C4, Canada (e-mail: vera.bril@utoronto.ca).

© 2005 Lippincott Williams & Wilkins, Inc.