Evaluation of the Stability of Small Ruptured Aneurysms with a Small Neck after Embolization with Guglielmi Detachable Coils. Correlation between Coil Packing Ratio and Coil Compaction

Abstract

It is difficult to predict the compaction of Guglielmi detachable coils (GDC) after endovascular surgery for aneurysms. Therefore, we studied the relationship between the coil packing ratio and compaction in 62 patients with acute ruptured intracranial aneurysms that were small (< 10 mm) had a small neck (< 4 mm) and were coil-embolized with GDC-10. We recorded the maximum prospective coil length, L, as the length that correspond with the volume of packed coils occupying 30% of the aneurysmal volume. L was calculated as L (cm) = 0.3 x a x b x c and the coil packing ratio expressed as packed coil length/L x 100, where a, b, and c are the aneurysmal height, length, and width in mm, respectively. Angiographic followup studies were performed at three months and one and two years after endovascular surgery. Of the 62 patients, 16 (25.8%) manifested angiographic coil compaction (ten minor and six major compactions); the mean coil packing ratio was 51.9 +/- 13.4%. The mean coil packing ratio in the other 46 patients was 80.5 +/- 20.2% and the difference was statistically significant (p < 0.01). In all six patients with major compaction the mean packing ratio was below 50%. We detected 93.8% of the compactions within 24 months of coil placement. In patients with small, necked aneurysms, the optimal coil packing ratio could be identified with the formula 0.3 x a x b x c. The probability of compaction was significantly higher when the coil packing ratio was under 50%. To detect coil compaction post-embolization, follow-up angiograms must be examined regularly for at least 24 months.

Figure 1

Plot graph showing the relationship between the coil packing ratio and aneurysmal volume (open circles;no compaction, black triangles;minor compaction, black circles;major compaction). The dotted line indicates a coil packing ratio of 50%

Figure 2

Bar graph showing the coil packing ratio in cases without-, with minor-, and with major coil compaction. The difference among the three groups was statistically significant (*p<0.01).

Figure 3

Timing of the manifestation of coil compaction in 16 patients with major (n=6) or minor compaction (n=10) on post-embolization follow-up angiograms (open circles, no compaction;black triangles, minor compaction;black circles, major compaction; large black circles, progressive major coil compaction; asterisks identify patients who underwent re-embolization).

Figure 4

A 58-year-old woman with a ruptured left ICA aneurysm and minor coil compaction. A) Left internal carotid angiogram showing an aneurysm at the paraclinoid portion. B) Left internal carotid angiogram obtained immediately after GDC embolization demonstrating complete aneurysmal occlusion. Left internal carotid angiogram obtained one year after GDC embolization demonstrating coil compaction and a small open C. space in the aneurysm. D) Left internal carotid angiogram obtained two years after GDC embolization demonstrating no change in the open space in the aneurysm.