A possible mechanism of isolated oculomotor nerve palsy by apoplexy of pituitary adenoma without cavernous sinus invasion: a report of two cases.

Isolated oculomotor nerve palsy occasionally occurs in patients with cavernous sinus invasion with or without pituitary apoplexy. We describe two cases of pituitary apoplexy without cavernous sinus invasion presenting with isolated oculomotor palsy. In both cases, computed tomography (CT) showed erosion of the right posterior clinoid process. Magnetic resonance imaging (MRI) depicted pituitary adenoma with apoplexy protruding latero-posteriorly to the right cavernous sinus. The medio-posterior wall of the cavernous sinus was markedly displaced latero-posteriorly by the tumor, and there was no evidence of cavernous sinus invasion. Oculomotor palsy may be caused first by unilateral erosion of the posterior clinoid process, resulting in latero-posterior protrusion of the adenoma. Hemorrhage may result in sudden kinking of the oculomotor nerve at the entrance of the oculomotor trigone.