Preliminary observation on predicting the need for coil extraction during microsurgery: the clip-coil ratio

Coil extraction during microsurgery for recanalized intracranial aneurysms can be associated with high morbidity. We evaluated our preliminary experience using the clip-coil ratio to predict the need for coil extraction. A multi-institutional retrospective review of previously coiled aneurysms that were clipped for recurrence between 2005 and 2009 was performed. The maximal height and the widths of the recanalization were measured. The largest of these dimensions was divided by the other. We defined this as the clip-coil ratio, which is a modification of the aspect ratio. Thirteen patients were included in this study. The mean age of the patients was 53 years (range 41-68 years). The aneurysm locations were anterior communicating artery (n = 5), pericallosal artery (n = 2), ophthalmic artery (n = 1), and posterior communicating artery (n = 5). A clip-coil ratio a parts per thousand yen1.3 allowed for microsurgical clipping without coil extraction. The mean ratio in these patients was 1.6. Coil extraction was necessary in two patients with a clip-coil ratio < 1.3. In reviewing our preliminary experience, we observed that coil extraction during microsurgery was not necessary when the clip coil ratio was a parts per thousand yen1.3. The ratio may serve as an indirect indicator of the amount of aneurysm tissue that can be incorporated within a clip; however, given the small patient population, further studies are needed to validate this concept.