• Kiyoyuki Yanaka, Yuji Matsumaru, Ryota Mashiko, Akio Hyodo, Koichi Sugimoto, and Tadao Nose.
• Department of Neurosurgery, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan. kyanaka@md.tsukuba.ac.jp
• Neurosurgery. 2003 Mar 1; 52 (3): 553-7; discussion 556-7.

ObjectiveSymptomatic unruptured aneurysms have been considered at relatively high risk for future rupture, and the majority of aneurysms that cause symptoms of mass effect are large. Unruptured aneurysms smaller than 1 cm in diameter sometimes cause neurological symptoms, but their clinical aspects remain obscure. In this article, we review our experience with small unruptured aneurysms presenting with oculomotor nerve palsy.MethodsSixteen patients with unruptured aneurysms smaller than 1 cm presenting with oculomotor nerve palsy were included in this study. The patients' clinical profiles were reviewed, and factors affecting the recovery of oculomotor function were determined.ResultsThe mean size of the aneurysms was 5.8 +/- 1.4 mm. Eleven patients (68.8%) had preceding retrobulbar pain. Fifteen patients underwent successful microsurgical clipping or intravascular embolization, but one patient died of aneurysm rupture before surgery. Seven patients (43.8%) had a complete recovery of oculomotor function, six (37.5%) had an incomplete recovery, and two (12.5%) remained unchanged after treatment. The mean interval between the onset of oculomotor nerve palsy and treatment was 4.7 +/- 3.3 days in patients with complete recovery, 24.2 +/- 15.5 days in patients with incomplete recovery, and 41.0 +/- 12.7 days in unchanged patients. Early surgery resulted in more complete recovery of neural function (P < 0.01).ConclusionUnruptured aneurysms smaller than 1 cm can cause neurological symptoms of mass effect. We recommend timely surgery, preferably within 5 days, to avoid not only aneurysm rupture but also functional disability even in patients with unruptured aneurysms smaller than 1 cm.

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