Trigemino-abducens synkinesis: an unusual case of aberrant regeneration

An unusual case of major head trauma is described involving injury to the right third, fifth, sixth and seventh cranial nerves in a basal skull fracture in a young woman. Two years later there persisted a total voluntary abducens nerve palsy, right facial hemianaesthesia and right temporalis and masseter palsy. However, involuntary abduction of the involved eye occurred on eating or chewing. Electromyography of the lateral rectus muscle documented aberrant reinnervation to support the clinical findings. Extraocular muscle surgery improved the compensatory head posture and minimized the chewing-induced abduction. The mechanisms for acquired synkinesis and the anatomy of the involved nerves are reviewed. It is postulated that regenerating motor fibres of the trigeminal nerve were misdirected along proprioceptive channels to the lateral rectus in the case reported here.