A brief history on determining occlusion of aneurysms by clips

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In 1996, when Gérard Debrun and his colleagues and our neurosurgical team were working with coiling of intracranial aneurysms, neurosurgeons were critical of the interventional approach because of the neck remnants or residuals left after coiling. Neurovascular surgeons believed that they completely occluded aneurysms without residuals. We searched the literature in 1996 and found only a few articles that examined the percentage of aneurysms that were incompletely clipped or in which a major vessel was occluded. That figure was 8% but was accepted with disbelief among neurosurgeons who believed that surgery was better than the coiling of aneurysms. In the article by Dashti et al in this issue, the authors report an incidence of neck residuals after clipping of 4% to 19% in their review of the literature, with an unexpected major vessel occlusion of up to 12%. No honest experienced neurosurgeon, who has clipped aneurysms, can believe that he or she has completely clipped every aneurysm they have treated. The geometry of the aneurysm can make complete clipping impossible. These anatomical factors promoting incomplete clipping do not account for those aneurysms in which the clips may occlude a major vessel.

In the past, visual inspection was the only method used to determine the adequacy of clipping. In the 1980s, a German scientist by the name of Eden developed a microvascular Doppler of 1 to 2 mm in diameter that could be used to determine qualitative flow in the vessels to and from an aneurysm. Dr J Gilsbach from Germany developed this technology, which was very good in determining the patency of the vessels after clipping. This instrument has been supplanted by a commercial device that is less precise but cheaper. Charbel introduced the quantitative microvascular flow meter in the late 1990s. This instrument could determine the actual flow in small-caliber vessels before and after aneurysm clipping to reveal if the aneurysm had compromised vessel flow. I have not seen his technology widely used.

Ophthalmologists have used indocyanine green video angiography for 30 years to detect blood flow under the microscope. Its use in neurosurgery was reported in the article by Dashti et al in this issue and by others. They used intravenously injected indocyanine green after clipping to determine if the blood containing the fluorescing indocyanine green was flowing without restriction in the vessels adjacent to the clipped aneurysm. This test is a visual analysis of flow. This technology requires an addition of a light source to the microscope to allow the fluorescence to be seen.

For those who cannot buy this equipment, complete exposure of all the vessels to and from the aneurysm is required. Actually, that should be done regardless of this technology. A complete understanding of the vascular anatomy of the aneurysm is critical before clipping. Temporary clipping that is available anywhere in the world is important to use in this exposure. Careful application of the clips to preserve the vessel anatomy is key and inspection of the aneurysm after clipping is required. The indocyanine green fluorescence method is very nice. An inexpensive Doppler may be helpful. Without any other help, the traditional ways of determining patency as described above are the best that can be offered, but obviously have the risks as the authors describe in their article.