The risk of bleeding from a cerebral saccular aneurysm has been estimated at about 1-2% per year. A current belief amongst neurosurgeons is that the larger the aneurysm, the higher the chance of rupture. This implies that small unruptured aneurysms may be considered benign.

     We conducted a local analysis of aneurysmal subarachnoid hemorrhage, with an emphasis on those ruptured lesions of small size.

     We identified 123 patients with a ruptured saccular aneurysm. Of these, 44 patients were treated by clipping and 79 patients via coiling.

     We retrospectively reviewed hospital records and radiological tests of all patients who presented to our tertiary care center with a ruptured saccular aneurysm from January 2008 to September 2011. The size of the dome and neck (in millimeters), aspect ratio (AR), and location of the aneurysms was determined using preoperative computed tomography angiography (CTA) and digital subtraction angiography (DSA).

     The average size of the dome, neck, and AR was 6.6±4.1 mm (range 5-26 mm), 3.1 mm, and 2.6±0.9, respectively. Forty-five patients (37%) had a ruptured aneurysm measuring less than 5 mm. For these small aneurysms (range 1.5-4.9 mm), the average size of the dome, neck, and AR was 3.9+1.1 mm, 1.6 mm, and 2.1+0.6, respectively. The anterior communicating artery was the most common location regardless of size.

     This is a retrospective study.

     Small aneurysms (<5 mm) are a substantial cause of aneurysmal subarachnoid hemorrhage in our center and should be considered lesions with potential for rupture.

     We suggest that size alone should not be the main characteristic in determining appropriateness of prophylactic aneurysm repair.