Posttraumatic abducens to oculomotor nerve misdirection

Introduction: Paradoxical patterns of extraocular muscle, eyelid, or pupillary movements can occur following injury between divisions of the oculomotor nerve, trigeminal and abducens nerves, and trigeminal and oculomotor nerves. We report three cases of unusual ocular motility and eyelid movements that are a result of aberrant connections between the abducens and oculomotor nerves. Methods: Three patients with unusual eye movement abnormalities after trauma were studied. A complete ophthalmic examination plus neuroradiologic evaluation were performed. Results: Each patient manifested an aberrant connection between the 6th and 3rd cranial nerves resulting in third nerve function during sixth nerve stimulation. Two patients demonstrated complete third nerve palsies except for adduction on attempted abduction. The third showed improved bilateral ptosis on abduction. Conclusions: The neuroanatomical abnormalities involve intraorbital structures in one patient and central nervous system pathways in the others. Explanations such as retrograde regeneration, ephaptic transmission, or denervation supersensitivity do not appear to explain these unusual eye movements. The most likely mechanism involves some form of peripheral neuronal misdirection. These rare sixth to third nerve misdirection cases add support to the “neuronal misdirection hypothesis” of aberrant eye movements after trauma.