Causes of early rebleeding after coil embolization of ruptured cerebral aneurysms.

OBJECTIVE: Early rebleeding after coil embolization of a ruptured cerebral aneurysm is rare but may cause severe disability or death. We present a case series of early rebleeding after coil embolization of ruptured cerebral aneurysms and investigate the incidence, clinical outcome and possible mechanism through retrospective analysis of angiographic and surgical findings. PATIENTS AND METHODS: This study included 347 consecutive patients who had undergone successful coil embolization of 347 ruptured cerebral saccular aneurysms. Clinical and angiographic data and findings from emergent surgery were analyzed retrospectively. RESULTS: Early rebleeding occurred in eight aneurysms (2.3%) and was especially frequent among anterior communicating artery lesions (6 out of 122, 4.9%). The other two events involved posterior communication artery lesions. The maximum diameter of the aneurysms that developed early rebleeding was 4.89 ± 0.65 mm, ranging from 3.9 to 5.7 mm. In seven out of eight patients, the immediate radiologically determined occlusion status was a residual neck, and the remaining patient had a residual sac. The coil packing density was between 21% and 34%. Six cases of rebleeding were detected within 48 h, 1 case was detected on the 5th day, and 1 case was detected on the 10th day. Coil compaction was not detected by follow-up angiography after early rebleeding. We performed surgical clipping as a rescue procedure in 5 cases and additional coil embolization in 1 case. During follow-up angiography and rescue clipping, inflow of blood to the aneurysm was detected in 6 cases. Three patients died, and the other 3 patients were severely disabled. The mechanisms of early rebleeding were divided into two types. First, blood may flow into the rupture site through a gap between the coil mesh and the aneurysm neck. Second, blood may enter the rupture site through the coil mesh due to insufficient thrombus formation. CONCLUSIONS: The early rebleeding rate after coil embolization of ruptured cerebral aneurysms in our study was 2.3%. The ruptured aneurysms were small in size (<6 mm), and rupture frequently occurred in the anterior communicating artery. In most cases, inflow of blood to the aneurysm was detected by follow-up angiography or during rescue surgery.