Management of failed flow diversion for intracranial aneurysm beyond the first 6 months of follow-up: an international Delphi consensus
Authors: Chintapalli Renuka , Nguyen Sarah , Taussky Philipp , Grandhi Ramesh , Dammann Philipp , Raygor Kunal , Tonetti Daniel A. , Andersson Tommy , White Philip , Ogilvy Christopher S. , Chapot Rene , Fox W. Christopher , Tawk Rabih G. , Lanzino Giuseppe , Hanel Ricardo , Jadhav Ashutosh , Hassan Ameer E. , Linfante Italo , Almefty Rami , Mascitelli Justin , Fargen Kyle , Levitt Michael R. , Burkhardt Jan-Karl , Jankowitz Brian T. , Jabbour Pascal , Starke Robert M. , Gross Bradley A. , Kan Peter , Killer-Oberpfalzer Monika , Rautio Riitta , Dmytriw Adam A. , Coulthard Alan , Dabus Guilherme , Raper Daniel , Deuschl Cornelius , Kilburg Craig , Budohoski Karol P. , Abla Adib A. 
Published: June 2024

OBJECTIVE
The placement of flow-diverting devices has become a common method of treating unruptured intracranial aneurysms of the internal carotid artery. The progressive improvement of aneurysm occlusion after treatment—with low complication and rupture rates—has led to a dilemma regarding the management of aneurysms in which occlusion has not occurred within 6–24 months. The authors aimed to identify clinical consensus regarding management of intracranial aneurysms displaying persistent filling 6–24 months after flow diversion and to ascertain questions that may drive future investigation.

METHODS
An international panel of 67 experts was invited to participate in a multistep Delphi consensus process on the treatment of intracranial aneurysms after failed flow diversion.

RESULTS
Of the 67 experts invited, 23 (34%) participated. Qualitative analysis of an initial survey with open-ended questions resulted in 51 statements regarding management of aneurysms showing persistent filling after flow diversion. The statements were grouped into 8 categories, and in the second round, respondents rated the degree of their agreement with each statement on a 5-point Likert scale. Flow diverters with surface modifiers did not influence administration of dual-antiplatelet therapy according to 83%. Consensus was also reached regarding the definition of treatment failure at specific time points, including at 6 months if there is aneurysm growth or persistent rapid flow through the entirety of the aneurysm (96%), at 12 months if there is aneurysm growth or symptom onset (78%), and at 24 months if there is persistent filling regardless of size and filling characteristics (74%). Although experts agreed that the degree of intimal hyperplasia or in-device stenosis could not be ascertained by noninvasive imaging alone (83%), only 65% chose digital subtraction angiography as the preferred modality. At 6 and 12 months, retreatment is preferred if there is persistent filling with aneurysm growth (96%, 96%), device malposition (48%, 87%), or a history of subarachnoid hemorrhage (65%, 70%), respectively, and at 24 months if there is persistent filling without reduction in aneurysm size (74%). Experts favored treatment with an additional flow diverter (87%) over aneurysm clipping, applying the same principles for follow-up (83%) and treatment failure (91%) as for the first flow diverter.

CONCLUSIONS
The authors present the consensus practices of experts in the management of intracranial aneurysms without occlusion 6–24 months after treatment with a flow-diverting device.