Marked Enlargement of a Fusiform Aneurysm in the Posterior Cerebral Artery after Circumferential Wrapping by Clip Reinforcement: Case Report.

Reinforcement or wrapping is frequently used to treat an unclippable fusiform aneurysm. However, reinforcement does not eliminate the aneurysm and therefore does not guarantee the prevention of bleeding or progressive growing of the aneurysm. Recently, we used a modified wrapping technique, including a clip-reinforced cotton sling to treat an incidental fusiform aneurysm at the P2 segment of the left posterior cerebral artery. The postoperative course was uneventful. Three months later, however, left-side oculomotor palsy developed, and angiograms showed a marked enlargement of the previously treated aneurysm. We suspect that the growing mechanism is related to changes in the properties of the aneurysmal wall after clip-reinforced wrapping. After clip-reinforced wrapping, the aneurysm becomes less flexible and experiences a greater wall stress. Therefore, if wrapping does not cover the full length of a fusiform aneurysm, the uncovered weak part of the aneurysmal wall may expand because of the increased wall stress.This clip-reinforced wrapping technique, though more reliable than the traditional wrapping technique, may induce a postoperative enlargement of fusiform aneurysms if incompletely performed.