Microsurgery and clipping: the gold standard for the treatment of intracranial aneurysms.

Craniotomy for microsurgical dissection and clipping remains the gold-standard treatment for intracranial aneurysms. It is the most time-tested, proven, and durable of available treatments for these lesions. The first craniotomy for clipping of an aneurysm has been attributed to Walter Dandy in 1937 (1). Dandy himself stated during that same time period “the surgical treatment of arterial aneurysms is exceedingly dangerous and so far, at least, has been unproductive of results” (2). Improvements in surgical techniques (particularly the addition of the operating microscope, aneurysm clips, and other microsurgical instrumentation), anesthesia, intraoperative monitoring techniques (3,4), and postoperative care have greatly advanced the ability to safely treat cerebral aneurysms since Dandy's time. Even as recently as 1976, the surgical mortality for patients with aneurysms of the anterior circulation in good preoperative condition was reported as high as 19% (5). Cerebral aneurysms remain a formidable clinical problem, but contemporary surgical series demonstrate that even the most challenging of cerebral aneurysms, such as those of the basilar apex, can be treated with microsurgical techniques with good resultant outcomes (6,7,8). The durability, safety, and efficacy of treatment of complex aneurysm such as these have yet to be matched by any endovascular technique. Optimal treatment for intracranial aneurysms continues to evolve and improve. For some aneurysms endovascular treatment seems to be better, for others microsurgery appears to be superior, but for many aneurysms, appropriate management may utilize either of these treatments. A number of factors must be taken into consideration when determining the best treatment strategy. Aneurysms that are associated with neurologic symptoms secondary to mass effect, either due to an associated intracerebral or subdural hematoma (9), or due to the giant size of the aneurysm (10) are most appropriately treated with open microsurgical techniques. Endovascular approaches do not allow for appropriate decompression of the mass lesion in these situations. Certain complex aneurysms necessitate a surgical bypass in order to obliterate the aneurysm and maintain adequate cerebral blood flow (11), such techniques likewise are not feasible through an endovascular approach. Outcomes from microsurgery for clipping of intracranial aneurysms continue to improve with advanced techniques such as intraoperative angiography for immediate determination of the adequacy of the clipping (12,13), and skull based approaches for improved surgical exposure (14). Microsurgery therefore remains a mainstay in the repertoire of the clinician caring for patients with intracranial aneurysms. Nonetheless, microvascular treatment of aneurysms does require a major surgical intervention, and in an effort to reduce morbidity, a number of so called “minimally invasive” endovascular techniques for the obliteration of aneurysms have been developed in recent years. These have included detachable balloons and, in the last decade, the development of Guglielmi detachable coils (GDC). Endovascular techniques continue to improve with development of a wide variety of catheter and coil types (15,16), adjuncts such as intraarterial balloon techniques for remodeling coils and protection of the native vessels (17), and in some cases, the placement of intraarterial stents. Newer strategies such as liquid agents, which polymerize upon deployment in an aneurysm are under investigation as potentially improved modalities for endovascular obliteration of aneurysms. Despite continued improvements, endovascular coiling is typically a viable option for only certain subsets of aneurysms, particularly smaller aneurysms with smaller necks, and in certain anatomic locations (for example, the basilar apex, or the ophthalmic segment of the internal carotid artery). Aneurysms in certain anatomic locations such as those of the middle cerebral artery bifurcation (18) are much less ideally suited for coils and are best treated with clips (3). Larger aneurysms, particularly those with thrombosed components, also are less than ideally obliterated with these coiling techniques.