Congenital trigemino-abducens synkinesis in a neonate

Congenital ocular synkinesis syndromes involve aberrant innervation of extraocular and eyelid muscles in a variety of patterns. A rare iteration is trigemino-abducens synkinesis, with only three published cases to date. Here the authors report (with video documentation) the earliest documented age of trigemino-abducens synkinesis and congenital ocular synkinesis in general. A 13-week-old (40-week postmenstrual age) girl presented with rhythmic abduction of the left eye that coordinated with sucking, likely resulting from abnormal embryologic development, causing activation of the lateral rectus by motor fibers of the mandibular branch of the trigeminal nerve.