Electromyographic studies on the coordination of antagonistic muscles in cases of abducens and facial palsy

Abstract

To illustrate the coordination between antagonistic muscles acting upon the eyeball and eyelid, a study was made of the electrical activity in the muscles of six patients with total abducens palsy, and ten with total facial palsy, and of five persons with normal eye movements. The eye was moved artificially in the latter cases by means of a bridle suture sewn to the attachment of the muscle. (1) Abducens Palsy.-In different positions of fixation with the sound eye and during movement of the gaze, the electrical activity in the internal rectus which is normally antagonist to the paretic muscle, showed a picture which would have been expected had the eye been able to assume normal positions and carry out normal movements. Activity successively decreased on movement of the gaze in the direction of the paretic muscle, and it disappeared entirely, or almost entirely, only when the non-paretic eye was turned strongly in that direction. The paretic eye had then not even reached the midline. These changes in activity are not bound to the act of fixation, for they are also observed when both eyes are incapable of fixation. The inhibitions of activity characteristic of the rapid phase of nystagmus also occur despite the total palsy of the muscle normally producing the movement. (2) Facial Palsy.-The activity in the levator palpebrae muscle followed the pattern seen in healthy subjects. On lowering the gaze the activity successively decreased, becoming entirely extinguished on extreme downward gaze. The lowering of the eyelid which takes place in spite of total palsy of the orbicuilaris muscle is thus caused, at least partly, by this inhibition. On strong effort to close the eyes a rapid and generally total inhibition was observed as in healthy subjects. (3) Compulsory Movement of Eye with Nornmal Motility.-No distinct change of activity in the internal or external recti muscle was caused by forcing the eye to perform movements or to assume various positions in relation to the other eye by means of a bridle suture. The activity corresponded to the subject's voluntary intentions as disclosed by the position of the non-captive eye.