Relation between aneurysm volume, packing, and compaction in 124 cerebral aneurysms treated with coils

PURPOSE: To assess the relation between aneurysm volume, packing, and compaction in cerebral aneurysms treated with coils. MATERIALS AND METHODS: The volumes of 145 aneurysms that were treated with coils were calculated with biplanar angiographic images and a custom-designed method. Partially thrombosed aneurysms were excluded. Packing was defined as the ratio between the volume of the inserted coils and the volume of the aneurysm and was calculated for all 145 aneurysms. Results at 6-month follow-up angiography were dichotomized into presence or absence of compaction. RESULTS: Aneurysm volume, packing, and compaction at 6-month follow-up were closely related. Large aneurysm volume was associated with low packing and frequent compaction. High packing prevents compaction. If the aneurysm volume was packed for 24% or more with coils, compaction did not occur in aneurysms with a volume of less than 600 mm(3). In small aneurysms with volumes of less than 200 mm(3), compaction did not occur when packing was above 20%. CONCLUSION: The common practice of inserting as many coils as possible in cerebral aneurysms is sensible in trying to avoid compaction. In aneurysms with packing of 24% or more, no compaction occurred at 6-month angiographic follow-up. In aneurysms with a volume of more than 600 mm(3), high packing could not be achieved which resulted in compaction in the majority of aneurysms.