Pupil-sparing oculomotor nerve paresis as an early symptom of unruptured internal carotid-posterior communicating artery aneurysms

Oculomotor nerve paresis caused by internal carotid-posterior communicating artery (IC-PC) aneurysm usually manifests with pupillary dysfunction. Recently, we treated three patients with unruptured IC-PC aneurysms initially manifesting as pupil-sparing oculomotor nerve paresis, which resolved after clipping of the aneurysms. Review of the 56 patients admitted to our hospital with unruptured IC-PC aneurysms between January 2000 and December 2006 identified 6 patients with oculomotor nerve disturbances, and the 3 present cases with pupil sparing. The incidence of IC-PC aneurysms manifesting as pupil-sparing oculomotor nerve paresis may be increasing with improved accessibility to medical services and wider awareness of oculomotor nerve paresis as a symptom of cerebral aneurysms. Cerebral angiography should be performed in patients with pupil-sparing oculomotor nerve paresis.