Primary internal ophthalmoplegia due to head injury.

Six cases of internal ophthalmoplegia due to direct head injury are presented. All six patients had a dilated, nonreactive pupil. Four had no extraocular palsies or ptosis and two had partial extraocular palsies or ptosis. Disturbance of consciousness was absent or very mild, and all patients fully recovered within 1 to 7 days after the traumatic event. No patient had a history that suggested a cause for oculomotor nerve palsy, and emergency CTscans showed no mass lesions. The internal ophthalmoplegia was recognized immediately after trauma. Although minimal oculomotor nerve palsies due to unruptured intracranial aneurysms have been described, none of our patients complained of periorbital or retroorbital pain either before or after the trauma, which rules out intracranial aneurysms as the cause of the internal ophthalmoplegia. Therefore, we concluded that the internal ophthalmoplegia was due to direct head injury. The pathophysiological mechanism of the internal ophthalmoplegia appeared to be slight injury of the pupillomotor fibres on the ventromedial surface of the third nerve at the posterior petroclinoid ligament, which acted as the fulcrum due to the downward displacement of the brainstem at the time of impact.