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Bonnie Sklar, Kalla A Gervasio, Khushmit Kaur, Mark Sivak, Albert Wu; Multi-electrode recording as a novel technique in electromyography of the orbicularis oculi muscle. Invest. Ophthalmol. Vis. Sci. 2018;59(9):332.
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Electromyography (EMG) is a non-invasive electrophysiology technique used to quantify the strength of muscle contraction. The orbicularis oculi is a non-uniform muscle responsible for blinking and is comprised of orbital, palpebral, and lacrimal portions. In clinical practice, EMG of the orbicularis oculi is conducted using a single, centrally-placed electrode to approximate the strength of the entire muscle circumference. This pilot study examined whether contraction of the orbicularis oculi varied significantly when EMG was performed with medially, centrally, and laterally placed electrodes.
Twenty-two EMG studies were recorded from the left and right orbicularis oculi muscles of 11 healthy adult volunteers. Postauricular electrical stimulation was performed by one technician at Mount Sinai Hospital. Recordings were obtained from medial (adjacent to the medial canthus), central (beneath the lower eyelid), and lateral (adjacent to the lateral canthus) electrodes. Measured EMG parameters included latency to contraction (ms), duration of contraction (ms), amplitude of contraction (mV), and area under the curve of contraction (mV-ms). Measured parameters were compared using ANOVA with a cutoff for p-value significance of <0.05.
There was a statistically significant difference between the mean area under the curve for the medial, central, and lateral electrodes (p=0.008; 4.68, 3.45, 4.57mVms respectively). The mean duration of contraction also significantly differed between the medial, central, and lateral electrodes (p=0.001; 6.59, 5.71, 7.72ms respectively). The mean amplitude of contraction trended upwards from lateral to medial but the difference was not statistically significant (p=0.23; 1.41, 1.34, 1.20mV). There was no statistically significant difference in mean latency for the medial, central, and lateral electrodes (p=0.98; 2.76, 2.75, 2.74ms).
Multi-electrode EMG of the orbicularis oculi provides more focal measurements of muscle strength rather than relying on a single electrode approximation of the entire muscle. More focused EMG information may be used in future studies to monitor improvement in or progression of abnormal muscle contraction seen in pathologies such as facial nerve palsy, blepharospasm, epiphora, brow ptosis, and ectropion. This information may enhance pre- and post-operative monitoring and inform surgical and medical decision-making.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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