Oculo-mandibular synkinesis.

Synkinetic movement of the mandible with ocular movement is a rare anomaly. Carmichael and Critchley (1925) noticed that, when the eyes were rapidly turned horizontally first to one side and then to the other, there was protrusion of the mandible with deviation to the contralateral side. The movement may be associated with depression of the contralateral and raising of the ipsilateral eyebrow. Walsh (I957) mentioned one case in which, besides these features, there was a concomitant contraction of the muscles of the ipsilateral side of the mouth. The jaw movement is often too slight and subtle to be satisfactorily documented by static photography, and we have therefore devised a method whereby oculo-fronto-mandibular synkinesis may be measured using the Vernier displacement principle to record the small lateral movement of the jaw.