Background Utility of the pipeline embolization device (PED) extending to the M1 segment as well as its clinical and flow consequences at the ICA bifurcation, has not clearly described. We describe clinical and anatomical flow modifications results at the ICA bifurcation.

Methods In this retrospective analysis of patients treated for distal supraclinoid carotid aneurysms, a single PED was deployed from the proximal M1 segment to the distal supraclinoid carotid. Flow assessment prior to the procedure, to predict the competence of the ACA/AcomA complex, was achieved by formal DSA angiography and occasional manual cross compression. In all cases a single PED was deployed over the ostium of the A1, while treating a single or multiple aneurysms.

Anatomical vessels diameters and ratios between the size of the proximal segments of the A1 and M1 as well as the distal ICA were assessed. Relationships between the PED nominal diameter and the diameters of the vessels at the landing zones were obtained. All measurements were evaluated in respect to flow modifications and size regression of the A1 in the immediate postoperative images, at 3 month MRI/MRA and at 6–9 month formal DSA angiography. Immediate and mid-term clinical results were assessed.

Results We treated seven patients using this technique. Median age was 62. Four patients were treated for multiple aneurysms. The following aneurysms were treated: 3 posterior communicating artery aneurysms, 3 anterior choroidal artery aneurysms, 4 ICA bifurcation aneurysms and one A1 segment aneurysm.

6/7 patients demonstrated no change of flow in ACA/AComA complex at the immediate post embolization angiography. One patient demonstrated immediate antegrade flow retardation in the ipsilateral A1 segment. Five patients underwent 3–4 month MRA follow up. All demonstrated size regression of the ipsilateral A1 segment and occlusion of the neurysms. Five patients underwent mid-term follow-up angiography (5.5–12 month). Complete reversal of flow in the ipsilateral A1, was noted in 4/5 patients (Figure 1). One patient did not demonstrate any flow modification. This patient had a dominant ipsilateral A1 segment. Interestingly, ratios of the vessels participating in this bifurcation demonstrated a unique configuration of a higher A1/M1, A1/ICA ratios and a lower M1/ICA ratio, possibly in favor of maintaining patency of the ipsilateral A1. In this specific patient, a minimal length (0.97 mm) of PED was deployed in the M1 segment. This was the most oversized PED in respect to the M1 segment.

All patients were stable in the post-procedural period and with no new neurological deficits. There were no clinical nor radiographic signs of ischemia. One patient experienced asymptomatic angiographic in-stent stenosis at the M1 segment.

Conclusions We found that the deployment of PED from the distal supraclinoid carotid to the M1 segment may result in reversal of flow in the ACA/AcomA complex as well as regression of the ipsilateral A1 segment. Preoperative anatomical disposition and sizing of the PED may predict the flow modification results. This modification of flow is safe and effective, based on pre-embolization flow assessments, and may be useful in treating distal ICA aneurysm by a flow diverter.

Disclosures E. Nossek: None. D. Chalif: None. S. Chakraborty: None. A. Setton: None.