Perhaps we should begin with a general statement regarding the relative merits of microsurgical and endovascular aneurysm treatment. We believe in the optimal situation (ie, these two different approaches are complementary rather than competitive); patients are best served when both treatment modalities are available and the final therapeutic decisions are tailored to best address the specific parameters of individual patients burdened with unique lesions. One size definitely does not fit all when one is dealing with aneurysms, and at University of Texas Southwest (UTSW), the practitioners of each of these modalities are heavily dependent on each other for advice, assistance, and even sometimes for rescue.

It was not too long after the advent of endovascular treatment of intracranial aneurysms in the early 1990s that neurosurgeons began to encounter patients in whom coil embolization had proven inadequate for complete or permanent aneurysm obliteration. In many, the long-term fate of such incomplete therapy was not known, whereas in others, symptoms related to the natural history of the aneurysm itself, mass effect on adjacent structures, or complications related to embolization appeared early in the posttreatment course. Since the emergence and maturation of endovascular techniques, the frequency of these treatment “failures” has markedly decreased, in part because of the dramatic improvements in endovascular technology and in part because there are fewer errors in patient selection by endovascular surgeons, both in our immediate referral base and across North America. As such, endovascular treatment has become the first-line therapy for an increasing proportion of aneurysm patients; however, several patients who require surgical treatment after previous endovascular therapy continue to present themselves. Given that these cases present certain unusual problems with regard to their technical management, we felt a brief chapter dedicated to this issue was appropriate.

Operating on a previously coiled aneurysm should generally be avoided for all the reasons that the aneurysm was coiled in the first place, which include patient comorbidities, patient preference, and difficult surgical location. On the other hand, if an aneurysm was coiled out of fear of a “hot brain,” which is now resolved, or if based on aneurysm morphology coiling was a misguided decision in the first place, or if attempts at recoiling have failed, surgery may be a practical option. New mass effect symptoms from growth of the previously treated aneurysm, from a new recurrence, or from the coil mass itself may also suggest the need for surgery.

Surgery on a previously coiled aneurysm carries several potential problems not encountered with de novo aneurysm treatment. First, the presence of the coil mass or an intracranial stent may interfere with permanent or even temporary clip placement. Second, the presence of the coil mass also reduces the elasticity of the neck–parent artery interface and thus increases the likelihood that a tear might develop when placing clip(s) across the neck. Finally, in rare cases, the presence of the coil mass may even limit access to the neck of the aneurysm. Nevertheless, with proper patient selection and surgical approach, an open surgical attack may be the patient’s best option. If the residual neck is larger than one and a half to twice the height of an aneurysm clip blade, it may be possible to secure the aneurysm without the need to open it or remove the coils. However, when the recurrence is small or the indication for re-treatment is mass effect, trapping the aneurysm, opening and then judicious coil removal may be necessary.

Anatomy

We have treated at least one patient with a partially coiled aneurysm in every location previously mentioned in this text except at the origin of the anterior temporal branch of the middle cerebral artery. The most common previously coiled aneurysm sites re-treated surgically have been the middle cerebral bifurcation, the origin of the ophthalmic artery from the internal carotid, the basilar apex, and the distal anterior cerebral artery. Because the majority of these patients have received their endovascular therapy elsewhere and were then referred to UTSW for consideration of further surgical intervention, a substantial portion of our reoperative experience stems from patients undergoing endovascular coiling at outside institutions. Regardless of origin, in all patients the decision to proceed with microsurgical treatment was made by our own neuroendovascular surgeons because further endovascular management was felt to be either unlikely to result in aneurysm obliteration or to carry more risk than a direct surgical approach. As time has progressed, an increasing number of these patients are being re-treated successfully by endovascular techniques. Besides the patients themselves, no one is happier with this trend than those of us who have had to deal with the peculiar problems posed by previously coiled lesions.