Abstract
Purpose: :
Facial nerve palsy results in decreased ability to blink, exposing the cornea to damage due to desiccation. It is not known if reanimation of the orbicularis oculi utilizing electric stimulation is possible. Previous studies have only attempted stimulation of the orbicularis oculi at a single location, without success. As the pretarsal fibers of the orbicularis oculi only span a third of the length of the muscle, it is unlikely that direct muscle stimulation of denervated muscle would be successful without simultaneous stimulation at multiple locations. Simultaneous stimulation at multiple locations has never been reported in humans, but has produced successful blinks in denervated orbicularis oculi in dogs (1). The purpose of this experiment was to determine if simultaneous stimulation at multiple sites is successful at producing a functional blink in denervated orbicularis oculi in humans.
Methods: :
Subjects were selected, with either acute or long standing facial nerve palsy. Exclusion criteria included any history of neuromuscular disease, or systemic condition that would affect the nervous system. Systematic testing of electric stimulation to tolerance was performed at seven locations of the pretarsal orbicularis oculi, individually and then simultaneously. Electromyography (EMG) and videography were used to characterize the response of the orbicularis muscle.
Results: :
Each subject tolerated stimulation intensity of at least 40mA but found intensities of greater than 3 mA uncomfortable. Maximal tolerable, yet uncomfortable, stimulation produced a muscle twitch without complete blink action in each location, as well as when performed simultaneously.
Conclusions: :
Simultaneous electric stimulation of the orbicularis oculi at locations spanning the entire upper and lower pretarsal orbicularis oculi does not produce a functional blink action in denervated human orbicularis oculi muscle.
References: :
1. Somia NN, Zonnevijlle ED, Stremel RW, et al. Multi–channel orbicularis oculi stimulation to restore eye–blink function in facial paralysis. Microsurgery 2001;21(6):264–70.