In the article Use of a Second Microcatheter in the Management of a Perforation during Endovascular Treatment of a Cerebral Aneurysm in this issue of the AJNR (page 1537), Willinsky et al present a novel and rational modification of the accepted strategy for managing a complication all too familiar to most interventional neuroradiologists. The authors left the initial microcatheter traversing the aneurysm dome while a second microcatheter was used to access the aneurysm and coil the lumen. The patient tolerated the event without any adverse sequelae.
Since its development in 1990, Guglielmi detachable coil (GDC) embolization of intracranial aneurysms has evolved from an experimental procedure to a well-accepted and widely performed method of protecting patients from subarachnoid hemorrhage. More than 30000 intracranial aneurysms have been treated worldwide, and the variables that affect the procedure's safety and efficacy are well documented. In considering the procedure's safety, it is worth noting that the two most common complications reported are thromboembolic and hemorrhagic, with the former significantly more common than the latter.
Intraprocedural aneurysm hemorrhage can be spontaneous or caused by overdrainage of a ventricular drain catheter, but more commonly might be caused by contrast overinjection or wire, catheter, or coil perforation. Of these, forward migration of the microcatheter is the most common cause of aneurysm rupture during GDC embolization. This emphasizes the importance of safe microcatheterization of aneurysms—reducing the risk for microcatheter jump by vigilant monitoring during microcatheter positioning, so that the forward progress of the catheter tip is commensurate with the forward progress of its shaft proximally. As a rule, the longer, the smaller in diameter, and the more tortuous the segment to be traversed by the microcatheter (from guide catheter tip to aneurysm) is, the more sites there are for friction between the microcatheter and vessel wall to accumulate (and suddenly release). One technique helpful in making microcatheter advancement more controlled is the triaxial technique. This technique, using a Tracker 38 as a middle catheter, effectively minimizes the potential build-up of friction, reducing the risk of microcatheter jump. In addition to these considerations, certain microcatheters are inherently more “jumpy” by virtue of their design characteristics. Braided catheters (including the microcatheter used in this case) are less likely to jump than nonbraided catheters.
Although microcatheter perforation into the subarachnoid space warrants an aggressive response, it must be kept in mind that not all cases of microcatheter tip migration beyond the confines of the aneurysm lumen represent perforation—catheters can migrate into the thrombosed portion of an aneurysm. In addition, not all aneurysm perforations are into the subarachnoid space. In the article by Willinsky et al, it appears at least possible that the perforation of the paraophthalmic aneurysm was into the cavernous sinus. The angiographic views provided suggest that this aneurysm had an intradural neck, but a dome extending into the cavernous sinus. These aneurysms can present with subarachnoid hemorrhage from the neck. The image of the microcatheter protruding through the dome shows a downward course. The patient suffered a very brief episode of mild hypertension, but did not display the classic Cushing hemodynamic response. Postprocedure CT images showed no new subarachnoid hemorrhage. The point is to confirm a subarachnoid location of the perforating catheter tip with an injection of a tiny amount of contrast, which would also confirm that reversal of heparin (with risks of clot formation, as occurred in this case) is truly necessary.
When aneurysm perforation into the subarachnoid space has occurred, quick response can salvage an ominous situation. Reversing the systemic heparin, achieving dense GDC packing of the aneurysm, and (if clinical signs of increased intracranial pressure or CT findings warrant) placing a ventricular drain constitute a strategy that can result in excellent neurologic recovery from an angiographically frightful hemorrhage. In describing the technique of leaving one microcatheter in place across the perforation while using a second catheter to coil the aneurysm, Willinsky et al have contributed a concept to our field that can improve the outcome of our patients.
An alternative strategy on the horizon is the use of liquid embolic agents. One such agent (Onyx, Micro Therapeutics, Inc) is currently being tested in clinical trials for aneurysm embolization. Liquid agents may be superior in the management of acute perforations and ruptures because, unlike GDC coils, these agents appear to seal the aneurysm lumen immediately.
Finally, it may be worthwhile to have a dialog within our specialty regarding the strategy of placing a coil across the perforation site, leaving it to transfix the wall of the aneurysm dome. As noted by Willinsky et al, this technique has been advocated in the management of intracranial vascular perforations. One must question, however, whether such placement of a coil is likely to seal the defect in a case such as the one they report (the defect represented a tear in a thin, abnormal aneurysm wall and was at least the diameter of the catheter—significantly larger than the diameter of the coil). One can also question whether the coil may impede healing of the perforation. Certainly there is a risk that the coil will exert tension on the edge of the tear because the coil itself is affected by blood flow within the aneurysm, CSF flow outside the aneurysm, and gravity. Unfortunately, there is no experimental or clinical data upon which one can base an answer to this question with respect to intracranial aneurysms. At present, the question of whether a GDC coil left transfixing an aneurysm wall defect improves or hinders hemostasis and healing is left to our intuition. It is an issue warranting objective investigation.
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