Treatment of Unruptured Cerebral Aneurysms: Coiling vs. Clipping
abstracts & commentary
Sources: Johnston SC, et al. Endovascular and surgical treatment of unruptured cerebral aneurysms: Comparison of risks. Ann Neurol 2000;48:11-19; Broderick JP. Editorial: Coiling, clipping or medical management of unruptured intracranial aneurysms: Time to randomize? Ann Neurol 2000;48:5-6.
Cerebral aneurysms increasingly are being discovered before they rupture either because they produce symptoms such as headache and cranial neuropathy, or because they appear as incidental findings on imaging studies. The likelihood of rupture of an aneurysm depends upon its size. Recently, an international study of unruptured intracranial aneurysms (UIA) reported that for UIAs less than 1 cm in diameter, the annual rate of rupture was less than 0.05% (International Study of Unruptured Intracranial Aneurysms Investigators. N Engl J Med 1998;339: 1725-1733). Larger or symptomatic aneurysms routinely are treated by surgically placing a clip over the neck of the aneurysm, or by inducing thrombosis of the aneurysm by endovascular placement of platinum coils. (Guglielmi G, et al. J Neurosurg 1991;75:8-14.) No randomized, prospective study has compared these two procedures
Johnston and colleagues conducted a blinded review of UIA-treated patients at the University of California San Francisco Medical Center since 1990. Three neurosurgeons and three neurointerventional radiologists determined feasibility and risk of treatment based on a retrospective review of clinical information and radiographic images, but without knowledge of the actual treatment or outcome. A change in Rankin Scale (Rankin J. Scott Med J 1957; 2:200-215) score of 2 or more from admission to discharge indicating a major procedure-related complication was the primary outcome measure. Long-term follow-up was by a mailed questionnaire and telephone interview.
Sixty-eight patients treated surgically and 62 treated with endovascular coil embolization were considered to have an anticipated procedure risk that was identical.
Twenty-five percent of surgical patients vs. 8% of endovascular patients developed a change in Rankin Scale score of 2 or more. Most of the cortical deficits suffered by surgical patients were due to focal ischemia caused by the process of clipping the aneurysm, or due to compression caused by brain retraction during the procedure. Total length of stay was longer (mean, 8 days vs 5 days) for surgical patients than for endovascular patients. At follow-up (average 4 years after the procedure), 34% of surgical patients vs. 8% of endovascular patients reported persistent new symptoms or disability since treatment. Time for 50% of patients returning to normal was one year for surgery and 27 days for coil embolization.
Johnston et al, therefore, concluded that endovascular coil embolization of UIAs is significantly safer than surgical clipping, particularly in the treatment of posterior circulation aneurysms.
Commentary
This important report offers evidence that endovascular coiling is safer than clipping in the treatment of UIA. As Broderick points out in his editorial, however, non-randomized retrospective studies have potential biases. For example, nearly one-half of the patients (61/130) had UIAs less than 1 cm in diameter and, therefore, could be expected to have a low rate of rupture and a good prognosis without treatment. Best medical therapy could have been a third treatment option in those patients.
Despite the favorable results from endovascular treatment, not all UIAs are amenable to endovascular coiling. Basilar tip aneurysms are relatively easy to access intravascularly but several turns need to be negotiated before a middle cerebral artery aneurysm is reached.
Finally, as Broderick suggests, the time is ripe for a randomized, multicenter U.S. trial comparing surgical and intravascular therapy for UIA. —John J. Caronna
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