Since the introduction of coiling as a definitive treatment for cerebral aneurysms, coils that are safer to use with both less risk of aneurysm rupture and coils that have lower aneurysm recanalisation rates have been the focus of development. The latest generation of coils include the very soft coils, wound round a central filament that is thinner and softer but retaining the stretch resistant properties of conventional coils.

We have found these coils particularly useful in patients with small, acutely ruptured aneurysms that are easily reruptured during coiling. Our experience with these coils has confirmed a very low complication rate <sup>[1Bilstra EH, Rinkel GJ, van der Graf Y et al. Treatment of intracranial aneurysms by embolization with coils: a systematic review. Stroke 1999; 30: 470-476

Cliquez ici pour aller à la section Références]</sup>. It has also been our impression that these coils pack more densely. Density of packing has been shown to correlate with durability of endovascular treatment and reduced compaction. Kanawabe et al. showed that packing densities of over 20% did not result in compaction in their series of 33 patients <sup>[3Sellar RJ, White PM, Moon P, Horrobin L. Coiling of very small aneurysms should be avoided? Neuroradiology 2001; 5: 417.

Cliquez ici pour aller à la section Références]</sup>. Whereas Tamatanis found that if 30% of the aneurysm volume was packed then it was stable <sup>[5Tamanati M, Yasuski I et al. Evaluation of the stability of aneurysms afterembolisation with detach able coils; correlation between stability of aneurysms and embolosed avolume of aneurysms. AJNR 2002; 23: 762-767.

Cliquez ici pour aller à la section Références]</sup>. Finally a Dutch group showed that if packing of over 24% occurred the recanalisation was unlikely <sup>[4Sluzewski M. Correlation of Coil packing density with aneurysm recanalisation. Presented at the advanced aneurysm course Oxford 2002.

Cliquez ici pour aller à la section Références]</sup>.

In this report we document our initial experience using a new very soft coil – UltiPaq^™ (Micrus, Sunnyvale, California) in a group of consecutive patients treated during a 10-week period. We treated 15 patients with 16 aneurysms using the UltiPaq^™ coil. 7 aneurysms were treated with UltiPaq^™ alone and 9 aneurysms were treated with MicruSphere™ spherical coils (Micrus) and the UltiPaq^™ coil. UltiPaq^™ has the advantage over other available very soft coils in that it has a short flexible detachment zone that does not leave a tail in the parent artery with subsequent possible thromboembolic complications.

The aneurysm volume was assessed on a purpose-designed programme that assumed the aneurysms were spherical or ellipsoid in shape. Nearly all the aneurysms fell into this category of shape. One aneurysm had a distal lobule (figure 1a) and the average volume was calculated by adding the volumes of the two ellipsoids (figure 1b). The cross sectional diameter of the coils was measured using a micrometer gauge which confirmed the manufacturer’s figures. Percentage occlusion of the aneurysm was assessed by two independent observers using the classification of Bilstra et al. <sup>[1Bilstra EH, Rinkel GJ, van der Graf Y et al. Treatment of intracranial aneurysms by embolization with coils: a systematic review. Stroke 1999; 30: 470-476

Cliquez ici pour aller à la section Références]</sup>(table I)andII).

13 out of 15 aneurysms were assessed to being 100% occluded by the coils. The exceptions to this were a sidewall PICA aneurysm (figure 2).

A small 1.5 mm aneurysm was also incompletely packed (figure 3). Both these aneurysms had vessels arising from the neck and complete coiling would have been at the expense of vessel occlusion. Aneurysms with wide necks or unfavourable dome to neck ratios were typically coiled with MicruSphere spherical coils initially and then with UltiPaq^™.

The density of the packing was very impressive (figure 1cand4) with a mean packing density of coils 38.1% of the total aneurysm volume. If spherical coils were initially used better packing ratios were achieved than when helical UltiPaq^™ coils alone were used 41.8% v’ s 33.9%. (p=0.05 using χ 2 test). The most likely explanation is that by conforming to the wall of the aneurysm more precisely than helical coils, greater density of packing can be achieved if a spherical coil or coils are deployed first. Indeed it implies that coiling spherical coils inside each other using the so-called “Russian Doll” technique may result in the greatest packing density. The density figures overall are impressive when compared to the figures that have been presented by the Dutch group <sup>[4Sluzewski M. Correlation of Coil packing density with aneurysm recanalisation. Presented at the advanced aneurysm course Oxford 2002.

Cliquez ici pour aller à la section Références]</sup> using different coiling systems. Densities over 24% only very rarely recanalised in their series. The aneurysms coiled were small with an average maximum diameter of 4.1mm and these smaller aneurysms were found to pack more densely than large aneurysms <sup>[3Sellar RJ, White PM, Moon P, Horrobin L. Coiling of very small aneurysms should be avoided? Neuroradiology 2001; 5: 417.

Cliquez ici pour aller à la section Références]</sup>.

The other characteristic is the malleability of the coils allowing treatment of aneurysms that are less than 2mm (figure 3) The aneurysm is incompletely coiled but our experience of these very small ruptured aneurysms is that partial coiling offers protection with complete healing often seen on later follow up <sup>[1Bilstra EH, Rinkel GJ, van der Graf Y et al. Treatment of intracranial aneurysms by embolization with coils: a systematic review. Stroke 1999; 30: 470-476

Cliquez ici pour aller à la section Références]</sup>.

No tails were identified in any of the cases — 2mm tails have been a problem with other very soft coil systems. No premature detachments, failure to detach or stretching of coils were encountered. Re-sheathing of coils that need to be withdrawn can be difficult but experience as well as using a swab held in the hand around the sheath creates more uniform pressure on the coil and helps to reintroduce the coil back into the sheath. No thrombo-embolic complications were encountered and the patients were not routinely anticoagulated after the procedure. No rebleeding has occurred to date with the longest follow-up at 5 months.