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Related Experiment Video

Updated: Jul 1, 2026

Dissection of Single Skeletal Muscle Fibers for Immunofluorescent and Morphometric Analyses of Whole-Mount Neuromuscular Junctions

Dissection of Single Skeletal Muscle Fibers for Immunofluorescent and Morphometric Analyses of Whole-Mount Neuromuscular Junctions

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Differential orbicularis oculi involvement in neuromuscular junction dysfunction.

Eleftherios S Papathanasiou¹, Eleni Zamba-Papanicolaou

¹Clinical Sciences, The Cyprus Institute of Neurology and Genetics, 6 International Airport Avenue, Nicosia 1683, Cyprus. neurophy@cing.ac.cy

Journal of Clinical Neurophysiology : Official Publication of the American Electroencephalographic Society

|September 16, 2008

Summary

The lower orbicularis oculi (OOc) muscle is more frequently abnormal in neuromuscular dysfunction than the upper OOc. Examining the lower OOc is crucial to avoid false negatives in myasthenia gravis diagnosis.

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Area of Science:

Neurology
Electrophysiology

Background:

Single-fiber electromyography (SFEMG) is a sensitive diagnostic tool for neuromuscular disorders.
Previous SFEMG normative values for orbicularis oculi (OOc) did not differentiate between upper and lower portions.

Purpose of the Study:

To investigate potential differences in dysfunction between the upper and lower orbicularis oculi (OOc) muscles using stimulated SFEMG.
To determine if the location of abnormality within the OOc impacts diagnostic accuracy for neuromuscular conditions.

Main Methods:

Prospective study including patients with suspected myasthenia gravis.
Utilized strict selection criteria for single fiber potentials during stimulated SFEMG.

Main Results:

Twenty-six of seventy-six patients completed the study with a final diagnosis.
Abnormal SFEMG results were observed in 21 patients.
The lower OOc demonstrated a higher incidence of abnormal potentials (27.6%) compared to the upper OOc (20.7%).
Lower OOc was solely abnormal in 7 patients, while upper OOc was solely abnormal in 2 patients.

Conclusions:

The lower orbicularis oculi (OOc) is a critical site for SFEMG examination in diagnosing neuromuscular dysfunction.
Targeting the lower OOc can help prevent false-negative results, particularly in suspected myasthenia gravis cases.