Acute expansion of an asymptomatic posterior communicating artery aneurysm resulting in oculomotor nerve palsy.

Acute expansion of an intracranial aneurysm is an extremely rare event. In this report, we describe the unusual radiographic documentation of acute expansion of a posterior communicating artery (PCOM) aneurysm from 4 to 8 mm, resulting in complete oculomotor nerve palsy. A 40-year-old man was admitted to our institution with a 3-week history of persistent occipital headaches but was otherwise neurologically intact. CT angiography demonstrated a 4 mm left PCOM aneurysm. Digital subtraction angiography performed several hours following presentation demonstrated an expansion in aneurysm size to 8 mm with new-onset complete oculomotor nerve palsy. The aneurysm was successfully obliterated by clip ligation. Although growth in aneurysm size is often a progressive phenomenon, acute expansions of aneurysms can occur.