Flow Diverter Therapy With the Pipeline Embolization Device Is Associated With an Elevated Rate of Delayed Fluid-Attenuated Inversion Recovery Lesions.

BACKGROUND AND PURPOSE Flow diversion using the Pipeline Embolization Device is reported as a safe treatment of aneurysms. Complete aneurysm occlusion, however, occurs in a delayed fashion with initial persistent filling of the aneurysm dome. We hypothesized that this transflow across metallic struts may be associated with thromboembolic events. METHODS Forty-one consecutive patients undergoing aneurysm treatment with the Pipeline Embolization Device and a comparison group of 78 Neuroform stent-mediated embolizations were studied. Patients' charts, procedure notes, platelet function, and anticoagulation state were analyzed. Serial magnetic resonance images were assessed for the presence of newly occurring diffusion-weighted imaging and fluid-attenuated inversion recovery (FLAIR) lesions at multiple postprocedure time ranges (average days post procedure [Pipeline Embolization Device/Neuroform]: T1=1, T2=73/107, T3=174, T4=277/335, and T5=409). In addition, diffusion-weighted imaging or FLAIR burden was estimated by lesional diameter summation. RESULTS Pipeline patients were more likely to have new ipsilateral FLAIR lesions at all time points studied (30.6% versus 7.2% of patients at T=2 and 34.5% versus 6.2% at T=4). The mean FLAIR burden was significantly increased for Pipeline patients (10.1 versus 0.7 mm at T=2 and 8.8 versus 1.9 mm at T=4). Overall 34% (14/41) of Pipeline patients experienced a new FLAIR lesion at anytime when compared with 10% (8/78) of Neuroform stent-coil patients. Postprocedural diffusion-weighted imaging did not predict future FLAIR lesions suggesting a nonprocedural cause. CONCLUSIONS The Pipeline Embolization Device is associated with increased rate of de novo FLAIR lesions occurring in a delayed fashion and distinct from perioperative diffusion-weighted imaging lesions. The cause and clinical effect of these lesions are unknown and suggest the need for prudent follow-up and evaluation.