Background An observation of increasing basilar artery curvature and progressive tilting of the aneurysms in large aneurysms (Figure 1) formed the basis of performing this retrospective evaluation of basilar apex aneurysms. Such progressive aneurysm tilting in large aneurysms can cause angiographic and symptomatic mass effect on the adjacent brain stem.
Methods An IRB-approved retrospective analysis of treated basilar apex aneurysms treated with endovascular approach was performed. The radius of curvature of the basilar artery was measured along its center line. The deformation of the basilar artery and aneurysm tilt was calculated as the difference in the radius of curvature (Figure 2) and the aneurysm angle on the initial compared to the follow up angiograms. The aneurysms were dichotomized into <10mm and ≥10mm based on maximum size.
Results A total of 63 basilar apex aneurysms met the inclusion criteria. There were 16 aneurysms in the ≥10 mm group and 47 in the <10 mm group. The mean radius of curvature on the initial angiogram was 35.6 mm (±21) and on the follow up angiogram it was 37 mm (±30). The mean aneurysm angulation compared to the distal basilar artery was 147 (±22) on the initial and 139 (±24) on the follow up angiograms. The difference between the pre and post radius of curvature was 7.7 mm (±8.7) for aneurysms ≥10 mm versus -4.2 mm (17) for aneurysms <10 mm (p = 0.009). The aneurysm tilt measured by the difference in angulation on the initial and follow up angiograms was 20o (±16) for aneurysms ≥10 mm versus 5o (±13) for aneurysm <10 mm (p = 0.0002).
Conclusion Large aneurysm (≥10 mm) can cause significant deformation of the basilar artery curvature and progressive aneurysm tilt compared to smaller aneurysms. Potential causes for this phenomenon may include mass effect from the coils or the flow dynamics and pulsatility associated with large aneurysms. Whether intrasaccular or intraluminal flow diversion will mitigate this phenomenon remains to be seen.
Disclosures A. Rai: 2; C; Stryker Neurovascular, Codman Neuro. S. Boo: None. J. Carpenter: None.
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