“It’s possible that it is less a problem with SILK and more a problem with medical management overall," Christoph J. Griessenauer says.
Delayed parent artery occlusion may occur in more than one in five patients treated with the SILK flow diverter (Balt Extrusion) for intracranial aneurysm, according to a Canadian retrospective analysis published online recently in the Journal of NeuroInterventional Surgery.
Ian R. Macdonald, MD, PhD, and Jai J. S. Shankar, MD, DM (Dalhousie University, Halifax, Canada), retrospectively analyzed a Canadian database of 34 patients treated for intracranial aneurysms using the SILK device between September 2010 and September 2017. Average clinical follow-up occurred at 31 months and imaging follow-up at 22 months.
Aneurysms treated using the SILK device were located in the anterior circulation in 27 patients and in the posterior circulation in seven patients. Occlusion of the parent artery was identified in 21% of patients between 8 days and 1.5 years from intervention. Among patients compliant with antiplatelet medication, the occurrence was 11.8% .
All parent artery occlusions were associated with aneurysms of the anterior circulation, and none were associated with neurological deficits. Aneurysms in patients who developed parent artery occlusions were more likely to have fusiform morphology than were aneurysms in nonoccluded patients (57% vs 19%; P = 0.039).
The presence of clinical symptoms at the time of the initial SILK flow diverter intervention was also significantly associated with development of parent artery occlusion (P = 0.021).
Underlying Cause of Occlusion Unclear
Commenting on the study for Neurovascular Exchange, Christoph J. Griessenauer, MD Geisinger Commonwealth School of Medicine, Scranton, PA., acknowledged that the high rate of parent artery occlusion is indeed worrisome, especially given that they mainly occurred in the internal carotid artery, which is a large vessel. What remains unclear to him, however, is whether this is due to some feature of the SILK device itself or simply to postsurgical patient management.
“[The study took place in] a Canadian center, so platelet function testing was not performed at all, and there is at least controversial evidence that platelet function testing for flow diversion is a critical thing,” he said, adding, “They did find an association between parent artery occlusion and premature [discontinuation of] dual antiplatelet therapy or noncompliance. Conceivably, the process of parent artery occlusion occurs either by endothelial hypertrophy . . . or thrombus formation. If [the latter] occurs, especially if you are not on appropriate dual antiplatelet therapy, that can explain these findings.”
In his center, as well as in many centers across the United States, antiplatelet therapy is given for 6 months after surgery, instead of the 3 months used in this series. In addition, most US centers have patients undergo routine antiplatelet testing, he said.
“In an effort to reduce noncompliance rates, we repeatedly perform platelet-function testing,” explained Griessenauer. “So, we are giving patients an incentive to continue the medication by showing that we really care about the way these medications are given and emphasize their importance. There are still going to be patients that are noncompliant, but we do everything in our power to make patients understand how critically important it is.”
Finally, Griessenauer pointed out that the clinical importance of parental artery occlusion in the absence of clinical symptoms remains a bit of an unanswered question when it comes to flow diverter treatment.
“If the patient has great collaterals, the carotid matrix can shut down and the patient may not even notice it unless you image it on screening. And then the question becomes, how relevant is that finding? The aneurysm is gone. It’s never going to come back,” he observed.
Griessenauer acknowledged that he has no direct experience with the SILK device, since it is currently not approved for use in the United States.
Macdonald IR, Shankar JJS. J NeuroInterv Surg. 2018;Epub ahead of print.
- Shankar reports serving as a proctor for SILK in Canada and receiving honorarium from Balt for flow diverter proctorship.
- Macdonald and Griessenauer report no relevant conflicts of interest.