36 Previously Clipped Recurrent Aneurysms of the Anterior Circulation
Abstract
Neurosurgical clipping of intracranial aneurysms is more likely to result in complete aneurysm obliteration compared to endovascular treatment, although the repair method to use depends on other factors such as the clinical outcome of the patient so that endovascular treatment often is recommended over clipping. Despite the high clipping repair efficacy, aneurysm remnants may be found immediately after aneurysm clipping in about 5% of patients. They may remain asymptomatic or lead to growth, hemorrhage, or symptoms such as mass effect. In addition, there rarely may be regrowth, hemorrhage, or symptoms due to regrowth of a previously completely clipped aneurysm or from a de novo aneurysm at another site. Management options for residual/recurrent aneurysms after clipping include no treatment, ongoing radiological surveillance, clipping or endovascular repair. Management decisions depend on patient and aneurysm factors as well as the estimated risks of repair.
Introduction
Randomized clinical trials found that endovascular repair of ruptured intracranial aneurysms gives better outcomes than neurosurgical clipping for aneurysms that can be treated by either method. As a result, the majority of aneurysms are now repaired by endovascular methods and there are fewer and fewer patients living with previously ruptured, clipped aneurysms. Another reason for the decline in these cases is that neurosurgical clipping is associated with lower rates of recurrence and retreatment compared to endovascular options. Unlike for acute repair of ruptured aneurysms, the evidence upon which to base decisions about whether to repair an unruptured aneurysm, if at all, are based on anecdotal evidence and, if a decision is made to treat, how to repair it also is not based on science.
Endovascular and open neurosurgical options provided by experienced physicians are recommended for the management of aneurysms that recur after clipping as they are rare, and repeat endovascular or intracranial surgery by themselves probably have an increased risk of complications.
Major controversies in decision making addressed in this chapter include:
Whether treatment is indicated or not, what follow-up, if any, is recommended.
Timing for intervention.
Open neurosurgical versus endovascular treatment for recurrent aneurysms previously clipped.
Whether to Treat
Treatment of recurrent aneurysms after clipping may be considered in several scenarios including (▶ Table 36.1 ):
Aneurysm remnants that are found immediately after aneurysm clipping in about 5% of patients ( 1 in algorithm ).
Regrowth, hemorrhage, or symptoms such as mass effect from a previously completely clipped aneurysm ( 2 in algorithm ).
Growth, hemorrhage, or symptoms from an aneurysm remnant known after clipping ( 2 in algorithm ).
New de novo aneurysms at site(s) distinct from the previously clipped aneurysm ( 3 in algorithm ).
This decision is based on assessment of the risks of treatment balanced against the risk of the natural history of the identified aneurysm, the natural history risk being basically the risk of recurrent hemorrhage. Some patients recover well after recurrent hemorrhage but for decision making, it is reasonable to assume that bleeding or rebleeding after aneurysm repair will lead to an unfavorable outcome. Surgeons have published retrospective reviews of their cases of craniotomy to clip previously clipped aneurysms. Morbidity and mortality is about 10%, but this is likely an underestimate and must vary with all of the usual factors that affect morbidity and mortality after aneurysm surgery. These factors include patient- (age, medical comorbidities, intracranial atherosclerosis) and aneurysm-related features (ruptured or not, presence of space-occupying intracerebral hemorrhage, aneurysm size, location, presence of calcifications and thrombus, presence of daughter loculi, and growth). Older age and associated medical illnesses increase the risk of complications. Ruptured aneurysms have worse outcome than unruptured aneurysms. Larger aneurysms and those with calcification and/or thrombus are more complicated to repair by any method. Increased size, presence of daughter sac, growth of the aneurysm, and posterior circulation location increase the risk of hemorrhage. When an aneurysm remnant is found after surgery, knowledge of why the remnant was left, either purposely or not, is important in deciding whether and how to repair (1, 2 in algorithm) .
The aforementioned risks of treatment have to be weighed against the risk of the recurrent aneurysm rupturing (▶ Table 36.2 ). The risk of aneurysm recurrence and hemorrhage following clipping has been studied in observational studies, but the data often include ruptured and unruptured aneurysms; have incomplete follow-up; lack information on whether the new aneurysm is growth of a residual, recurrence; or de novo; and if the recurrence has hemorrhaged or not. The annual recurrence rate of completely clipped, ruptured, or unruptured aneurysms is 0.26 to 0.52%. De novo aneurysms form in patients with intracranial aneurysms at 0.84 to 2.2% per year and this must be higher than the risk of recurrent subarachnoid hemorrhage (SAH), although the rates (0.79–1.9% per year) overlap with overall recurrence rates.
Most recurrent aneurysms, like aneurysms in general, are in the anterior circulation. A reasonable assumption would be that the risk of hemorrhage from recurrent aneurysms after complete clipping and from de novo aneurysms approximates that of an unruptured aneurysm. This risk is higher with increased aneurysm size, posterior location, and history of SAH; so, these factors need to be taken into account when determining management ( 2, 3 in algorithm ).
The time from initial treatment to retreatment in most studies is about 10 years for recurrent and de novo aneurysms. Remnants after initial surgery for aneurysm repair should be detected by intraoperative means such as indocyanine green (ICG) or intra-arterial contrast angiography and in these cases, such remnants of the aneurysm can be left alone or treated right away by endovascular means. If intraoperative imaging is not done, then various other unexpected findings can arise that may be treated with reoperation, endovascular methods, or observation.
Aneurysm Detected Immediately after Surgery
If the surgeon does the best clipping they can and document a residual aneurysm by intraoperative means, then they need to decide after the surgery whether to observe the remnant or to endovascularly coil it. If intraoperative imaging is not done, then unexpected findings can occur such as filling of the aneurysm distal to the clip blades, presence of a residual proximal part of the aneurysm, or finding a completely unclipped aneurysm ( 1 in algorithm ). Aneurysm filling distal to the clip blades carries a high risk of rebleeding for ruptured aneurysms and alters the hemodynamics of unruptured aneurysms, potentially leading to catastrophic hemorrhage ( 1 , 5, 8 in algorithm ). Therefore, in general, distal filling should be treated immediately by surgical exploration or endovascular means with the decision based on the usual factors such as the clinical condition of the patient, the surgeon′s impression as to the cause of the remnant, and the potential efficacy of repeat clipping or endovascular repair (▶ Fig. 36.1 ). The same considerations apply to unexpected proximal remnants, although their risk of rupture is probably low whether or not the initial indication for treatment was hemorrhage or not and approximates that of unruptured aneurysms ( 2, 6, 7, 9 in algorithm ).
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