Endovascular occlusion of intracranial aneurysms with Guglielmi detachable coils: correlation between coil packing density and coil compaction.

This retrospective analysis was undertaken to evaluate a possible relationship between coil packing density and coil compaction on intracranial aneurysms embolized using Guglielmi detachable coils (GDCs). Of the patients who underwent endovascular surgery using GDC in our hospital between 1994 and 1998, 33 patients had endovascular treatment with GDC and were examined by follow-up angiography at least 12 months after surgery. They had coil embolization to the extent where aneurysms were no longer filled or only faintly filled as shown by cerebral angiography immediately after surgery. At follow-up angiography, coil compaction was observed in 3 aneurysms. In all patients with coil compaction, the coil packing density was below 20% (14.5 +/- 4.0%). On the other hand, it was over 20% (25.7 +/- 4.7%) in all patients without coil compaction. In the 11 patients with a basilar bifurcation aneurysm, the coil packing density was over 24% and no coil compaction was observed. The coil packing density seems to be one of the critical factors, particularly for predicting whether or not coil compaction will occur. Endovascular surgery should be performed to obtain coil packing density higher than 20%.