Diagnostic utility of stimulated single‐fiber electromyography of the orbicularis oculi muscle in patients with suspected ocular myasthenia

Abstract

Stimulated single-fiber electromyography (SSFEMG) is a valuable diagnostic tool in cases of myasthenia gravis with limited disease. From 1990 to 2008 SSFEMG in the orbicularis oculi muscle (OO) was performed in a cohort of 456 patients referred with clinical suspicion of myasthenia gravis (MG) and exclusively ocular symptoms. A diagnosis of MG was made on clinical grounds in 103 patients. In this patient cohort, the specificity of SSFEMG for myasthenia was 97%, and the sensitivity was 80%. MG patients with a normal SSFEMG had a benign clinical course. This study confirms a high specificity and sensitivity of SSFEMG when it is performed on patients suspected to have ocular MG. In such patients, a normal SSFEMG of the OO predicts a benign clinical course.

Clinical Reasoning: A case of acute onset bilateral ptosis in a young child

“…SSFEMG of the orbicularis oculi muscle in ocular myasthenia is highly specific (97%) and the sensitivity approaches 80%. 3 There were no systemic signs or encephalopathy to suggest an infection or inflammatory disorder requiring specific treatments.…”

The evaluation of blepharoptosis etiology from the point of forensic medicine

“…Ptozise telekantus, epikantus, inversus vs nin eşlik ettiği durumlarda konjenital etyoloji daima ön plandadır (6,2,7,37 (2,11,12).…”

“…Bununla birlikte şaşılığın düzel-tilmesi ile ptozis ortadan kalkabilir. Ptozis ile birlikte diplopi, Myastenia Gravis'i düşündür-melidir (11,12).…”

Ocular Myasthenia Analysis of Diagnostic and Treatment Options

“…The sensitivity of repetitive nerve stimulation for OM is poor (11-54 percent), but specificity is high (89-98 percent) (Roh et al 2011). Evaluation of the orbicularis oculi (especially the lower orbicularis oculi), orbicularis oris, or nasalis will increase the percentage of patients identified, but such evaluations are much more difficult to tolerate for patients than extremity evaluations (Mercelis and Merckaert 2011). Although identification of decremental responses in non-ocular muscles indicates subclinical disease in other muscles, the finding does not indicate the presence or predict progression to generalized MG.…”

“…If the mean jitter -time between activation of all fiber pairs (or endplates) -exceeds the upper limit of normal for that muscle, or if more than 10% of pairs have jitter that exceeds the upper limit of jitter during voluntary activation, then the study is considered abnormal. SFEMG is 62 to 99 percent sensitive for detection of MG, and its specificity is reported to be from 66 to 98 percent (Ukachoke et al 1994;de Entrambasaguas et al 2007;Mercelis and Merckaert 2011); however, it implementation is limited due to the requirements of specially-trained, experienced examiners. Although it is labor-intensive, SFEMG should be considered in patients with a strong clinical suspicion for OM in which repetitive nerve stimulation is negative, due to its higher sensitivity (Srivastava et al 2007).…”