Intracranial aneurysm surgery and its future
Authors: R S Maurice-Williams, J Lafuente
Journal: Journal of the Royal Society of Medicine (2003)

The history of intracranial surgery for aneurysms is not a long one. The first direct operation on an intracranial aneurysm was performed by Norman Dott, who wrapped a ruptured aneurysm in 1933,1 and the first obliterative clipping of an aneurysm was performed by Walter Dandy in 1938.2 The results of surgery improved dramatically when the operating microscope was introduced in the 1960s3 and a subsequent improvement followed the use of the calcium antagonist nimodipine and the maintenance of a high fluid intake to lessen the risk of delayed cerebral ischaemia.4

For many years clipping of a ruptured aneurysm was regarded as the definitive mode of treatment, but the development of the GDC coil in 1990 allowed an alternative approach that avoided the hazards of open surgery. In the latter half of the 1990s, as experience of endovascular techniques spread, this form of treatment began to displace open surgery and the International Subarachnoid Aneurysm Trial (ISAT) was set up to compare the efficacy of the two forms of treatment.

Early in 2002 the trial was interrupted by the steering committee when an intermediate analysis of the results revealed that, in the short term at any rate, the results of endovascular coiling were superior to those of clipping, in that the chances of survival free of disability at one year were significantly better for coiling. Furthermore, the risk of rebleeding from a successfully coiled aneurysm at one year was only 0.16%.5

Although this still leaves open the long-term risks of aneurysm re-formation and rebleeding after coiling (a risk which is negligible after successful clipping), we believe that the results of ISAT must spell the end of aneurysm surgery—though no doubt there will be a transitional period of some years before surgery finally disappears. As things stand, it is difficult to advise surgery in those cases where coiling is practicable, and publication of the ISAT probably led to an immediate shift towards coiling in most units in the UK.

The current margin in favour of endovascular treatment is likely to increase in the future, for the following reasons. Endovascular as opposed to surgical treatment is an evolving technique. Not only is the microtechnology constantly improving but also more and more neuroradiologists are acquiring and honing their skills in this field. As this happens, increasing proportions of aneurysms are proving amenable to endovascular treatment. By contrast, the technology of surgery has been static for many years and, after the quantum leap in results provided by the introduction of the operating microscope and associated microinstrumentation, it is difficult to see how the techniques of open surgery could be further improved. Furthermore, as the use of endovascular techniques extends, so the surgical expertise will be lost. Already the pool of very experienced surgeons is draining away as a result of death and retirement, and as these surgeons disappear the advantages of endovascular treatment will become greater still. The number of cases unsuitable for endovascular treatment will shrink to the point where there will be a residue of difficult and complex cases for which only surgery is available. However, it is by no means certain that surgery would be justified in such cases. These are likely to be patients with, for example, giant and complex aneurysms in inaccessible situations where even at present surgical as opposed to conservative treatment may be difficult to justify. This will be still more true when the surgical skills honed upon hundreds of more straightforward cases have been lost.

For these reasons, any review of aneurysm surgery must be largely of historical interest. However, we think it of value to touch on some topics that have concerned the senior author in the course of 30 years of aneurysm surgery during which time he has treated almost a thousand cases. Over this period he had prepared prospective datasheets for every patient treated under his care. These datasheets have provided much information on the clinical course of the patients treated, the technical difficulties encountered at surgery and the postoperative problems that arose.