Electrophysiological study of the denervated orbicularis oculi muscle in dogs

A blinking periorbital prosthesis using surface electromyographic signals of the orbicularis oculi muscle

BACKGROUND

Recent advances in human-machine interface technology have enabled the development of multifunctional, primarily orthopedic myoelectric prostheses. We developed a noninvasive blinking periorbital prosthesis that can synchronize with blinking of the intact eyelid by using surface electromyographic signals of the orbicularis oculi muscle.

METHODS

Myoelectric potentials of the orbicularis oculi muscle while blinking were measured with surface electrodes on the eyelid in four healthy adults. Possible cross talk introduced via the electrodes was also measured and assessed to determine whether cross talk would affect surface electromyographic measurements while blinking.

RESULTS

The amplitude of the surface myoelectric potential of the orbicularis oculi muscle was sufficiently high for the practical use of blinking prostheses. Our blinking model was successfully synchronized with blinks of the subjects' eyelids under experimental conditions without cross talk between the orbicularis oculi muscle and other muscles.

CONCLUSIONS

Although our study revealed several problems, the use of surface electromyographic signals could be a promising and useful technique for synchronizing blinking of the prosthetic eyelid with blinking of the intact eyelid. Level of Evidence: Level V, therapeutic study.

Multi-channel orbicularis oculi stimulation to restore eye-blink function in facial paralysis

Facial paralysis due to facial nerve injury results in the loss of function of the muscles of the hemiface. The most serious complication in extreme cases is the loss of vision. In this study, we compared the effectiveness of single- and multiple-channel electrical stimulation to restore a complete and cosmetically acceptable eye blink. We established bilateral orbicularis oculi muscle (OOM) paralysis in eight dogs; the OOM of one side was directly stimulated using single-channel electrical stimulation and the opposite side was stimulated using multi-channel electrical stimulation. The changes in the palpebral fissure and complete palpebral closure were measured. The difference in current intensities between the multi-channel and single-channel simulation groups was significant, while only multi-channel stimulation produced complete eyelid closure. The latest electronic stimulation circuitry with high-quality implantable electrodes will make it possible to regulate precisely OOM contractions and thus generate complete and cosmetically acceptable eye-blink motion in patients with facial paralysis.

Restoration of paralyzed orbicularis oculi muscle function by controlled electrical current

A canine model of facial nerve paralysis was studied to apply controlled electrical current to the peripherally denervated orbicularis oculi muscle, in the attempt to effectively restore the absent function of this denervated muscle. After unilateral facial nerve neurotmesis was performed in eight dogs, the denervated orbicularis oculi muscles of four dogs were electrically stimulated for 75 postoperative days (40 min/day). Denervated and normal orbicularis oculi muscles were electrophysiologically studied and compared with the Student t test. During the study period, minimum closure of denervated treated orbicularis oculi muscles was evoked with average stimulus strength (80-ms duration) of 1.61 +/- 0.22 log mA x ms, not significantly different from that of denervated nontreated or normal orbicularis oculi muscles. From days 10 through 30 only, maximum closure of denervated treated orbicularis oculi muscles was achieved with mean pulse strength (80-ms duration) of 2.37 +/- 0.09 log mA x ms, significantly lower (P less than .01) than that evoking the same type of contraction from denervated nontreated muscles (80-ms duration, mean 2.83 +/- 0.10 log mA x ms). In addition, denervated treated muscle pulse strength eliciting maximum contraction was not significantly different from that of normal orbicularis oculi muscles during the same period. This finding was not observed, however, from day 40 through the end of the study. This investigation demonstrates (1) the transient reversal of denervation changes of paralyzed orbicularis oculi muscle by daily electrical stimulation, and (2) the feasibility of restoring orbicularis oculi muscle function by controlled electrical current.