Rare Case of Post-Traumatic Abducens-Oculomotor Nerve Synkinesis Exhibiting Unusual Ocular Motility.

Abstract

BACKGROUND Acquired synkinesis is a well-known phenomenon following oculomotor nerve injury. The abnormal movement appears within the distribution of 1 nerve, or other cranial nerves may be involved. The common misdirection of aberrant regeneration of oculomotor nerve involves the lid, extraocular muscles, or pupil. This report presents a case of aberrant connection between abducens and oculomotor nerve, which is quite rare. CASE REPORT A 21-year-old man with history of left-sided frontal, lateral orbital wall, and zygomatic fracture from head trauma in a motor vehicle accident presented for evaluation. He was comatose for 6 weeks in the intensive care unit. Six months later, he presented to the ophthalmology clinic for an eye examination. He had no history of eye problems prior to this accident. His best corrected visual acuity in the right eye was 20/20 and the left eye had no light perception. The right eye exam was normal, with normal ocular motility. The left eye exam showed small esotropia in primary position with markedly decreased adduction, elevation, and minimal depression, but on attempted abduction, the left eye would adduct instead. There was no globe retraction when left eye abduction was attempted. The abnormal movement seen resulted from third nerve function during sixth nerve stimulation, due to unusual ocular motility with abnormal connection between the sixth and third cranial nerves. CONCLUSIONS The most likely pathophysiologic mechanism here is peripheral neuronal misdirection hypothesis after trauma. Careful and detailed examination of a patient presenting with unusual ocular motility after trauma is very important. The abnormal connection between the sixth and third cranial nerves is quite rare but can occur.