Valko Y, Rosengren SM, Jung HH, et al. Ocular Vestibular Evoked Myogenic Potentials as a Test for Myasthenia Gravis. Neurology 2016;86:660-668.
Submitted by Andrew Tarulli, MD, News Science Editorial Board
Valko and colleagues describe the use of ocular vestibular evoked myogenic potentials (oVEMP) in patients with myasthenia gravis. The technique is based on the vestibulo-ocular reflex, and involves application of a repetitive vibratory stimulus to the skull with a mini shaker and recording of evoked responses from the inferior oblique muscles using facial electrodes. Thirteen patients with isolated ocular myasthenia gravis and 14 with generalized myasthenia gravis were studied, and compared to 28 healthy controls. All of the patients with generalized myasthenia gravis had ocular symptoms and 7 of the 27 myasthenics were seronegative for both acetylcholine receptor and MuSK antibodies. oVEMP using a unilateral decrement of 15.2% or greater produced a sensitivity of 89% and a specificity of 64% for myasthenia gravis, while a bilateral decrement of 20.4% or greater produced a 100% specificity, but a sensitivity of only 63%.
Comment: oVEMP may be a useful test for evaluation of patients with myasthenia gravis. It offers two potential advantages compared to currently available techniques. First, the extraocular muscles are directly accessible, which is not true of any currently used technique. Second, the sensitivity for ocular myasthenia gravis may be greater than antibody assays, single fiber electromyography, or repetitive nerve stimulation. Further refinement of the technique in larger groups of subjects (with particular attention to defining cutoffs for normal and abnormal) and application of oVEMP in a prospective fashion are necessary before it is applied widely.
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