Modifying Flow in the ICA Bifurcation: Pipeline Deployment from the Supraclinoid ICA Extending into the M1 Segment—Clinical and Anatomic Results

BACKGROUND AND PURPOSE: Utility of the Pipeline Embolization Device extending to the M1 and its clinical and flow consequences at the ICA bifurcation have not been characterized. We analyzed flow modification in cases where a single Pipeline Embolization Device was deployed from the M1 to the distal supraclinoid ICA, covering the A1, for aneurysm treatment.

MATERIALS AND METHODS: A1 flow modifications and size regression in postprocedure and follow-up angiography were analyzed. Vessel diameters and ratios of the proximal A1 and M1 segments and the distal ICA were assessed. Relationships between Pipeline Embolization Device nominal diameter and the vessel diameters at landing zones were obtained. Clinical assessments after flow modification were documented.

RESULTS: Six of 7 patients demonstrated no change of flow in the anterior cerebral artery/anterior communicating artery complex at immediate postembolization angiography. All patients who underwent follow-up angiography demonstrated size regression of the ipsilateral A1. Midterm follow-up angiography revealed complete reversal of flow in the ipsilateral A1 in 4 of 5 patients. One patient did not demonstrate flow modification. This patient had a dominant ipsilateral A1. Vessel ratios in this case demonstrated a unique configuration in favor of maintaining patency of the ipsilateral A1. There were no clinical or radiographic signs of ischemia. One patient experienced asymptomatic angiographic in-stent stenosis at the M1.

CONCLUSIONS: We found that deployment of a Pipeline Embolization Device from the distal supraclinoid ICA to the M1 may result in reversal of flow in the anterior cerebral artery/anterior communicating artery complex and regression of the ipsilateral A1. Preoperative anatomic quantitation and sizing of the Pipeline Embolization Device may predict flow modification results.