The rebleeding or regrowth of cerebral aneurysms treated with a clip may possibly occur a long time after operation. The authors have experienced four such cases. The occurrence rate was 0.64% of all clipped aneurysms (691 cases) in our institute. The location of the aneurysms were, Acom A in two cases, distal ACA in one and BA tip in one; and all of them were initially operated on the chronic SAH stage, and were treated with spring clips.
They showed good postoperative courses, but problems developed in 24-64 months (mean: 46.25 months) after the intial operations. In all cases another operation was then performed. From the findings of the second operation, we determined the causes to be as follows: 1) In two cases the clips had slipped out. At the first operation, it had not been possible to completely obliterate the necks of the aneurysms because of the need to avoid kinking the parent arteries, or to spare tightly adhering perforating arteries. The pulsative forces to the necks of the aneurysms over a long period seemed to have caused clip slipage.
2) In one case, abnormal aneurysmal dilatation was found in the neck beneath the clip, but the clip had not slipped out. The possible mechanism of the dilatation of the neck was thought to be similar to those of the two cases mentioned above.
3) In one case, a small new aneurysm was found adjacent to the clipped aneurysm. The reason for the appearance of this new aneurysm could not be determined.
Many authors have reported possible reasons for the recurrences of clipped aneurysms and some methods to prevent such recurrences.
From the facts we mentioned above, although it is a matter of course, we suggest that greater effort to isolate the neck of the aneurysm or to clip the isolated neck correctly is the best way to prevent recurrences. And if perfect neck clipping is not possible, additional, firm coating of the clipped aneurysm with appropriate materials should be performed.