Traumatic oculomotor nerve palsy.

Traumatic isolated oculomotor nerve palsy is not common. Oculomotor nerve palsy without internal ophthalmoplegia (pupil sparing) is extremely rare. We report a case of this condition in a child. An 11-year-old boy was transferred to our hospital after a head injury in a traffic accident. Neuro-ophthalmic examination showed that the left eye had limited adduction, supraduction, and infraduction, incomplete convergence and left ptosis, but no internal ophthalmoplegia. Magnetic resonance imaging indicated mild bending of the ipsilateral oculomotor nerve at the posterior petroclinoid ligament. One month after injury, movement of the patient's eyes was normal on examination, but there was mild diplopia. The suggested mechanism of the oculomotor nerve palsy with pupil sparing in this case is stretching of the oculomotor nerve at the posterior petroclinoid ligament, maintaining an intact pupillomotor nerve.