Pathogenesis of primary internal ophthalmoplegia after head injury

Primary internal ophthalmoplegia is a rare ocular syndrome after head injury. Its pathogenesis remains unclear and it is only a hypothesis that the pupillomotor fibres on the ventromedial aspect of the oculomotor nerve are slightly contused against the petroclinoid ligament at the moment of impact. We observed a patient after head injury who presented with a fixed, dilated pupil and died within 15 hours of the accident. The postmortem examination revealed an isolated group of fibres on the medial aspect of her oculomotor nerve, which had been torn out of the midbrain. This suggests an alternative explanation in terms of partial injury to the oculomotor nerve to account for primary internal ophthalmoplegia.