There are technical difficulties that may be encountered during endovascular coiling for saccular vertebral artery-posterior inferior cerebellar artery (VA-PICA) aneurysms because some have unfavorable morphology such as a side branch arising from the aneurysm neck and a shallow aneurysm dome. We analyzed the clinical and radiological outcomes of endovascular coiling for saccular VA-PICA aneurysms. We also investigated morphological factors associated with coiling success and failure to evaluate the safety and feasibility of this treatment. Between March 1997 and September 2012, we treated 24 cases (19 ruptured and five unruptured aneurysm cases) of saccular VA-PICA aneurysms with endovascular coiling. All 24 aneurysms demonstrated a side-branch arising from the neck on digital subtraction angiography. Twenty cases with VA-PICA aneurysms were successfully embolized with coiling while there were four failures. One ruptured case experienced symptomatic ischemic complication that resulted from delayed distal coil migration. An aspect ratio of ＜1.2 and an aneurysm-parent artery angle of ＜90° were associated with failure of endovascular coiling. Of the 20 coil-treated aneurysms, immediate angiographic results showed near-complete aneurysm occlusion in 12/20 (60.0%) cases, neck remnant in five (25.0%), and residual aneurysm in three (15.0%). One patient (5%) had a major aneurysm recurrence that was uneventfully reembolized. Thirteen of 19 ruptured cases (68.4%) cases had good outcomes (modified Rankin Scale 0–2), two (10.5%) had moderate disability (mRS 3), and one (5.3%) had severe disability (mRS 4–5) at three months after treatment.
The results of this study suggest that endovascular coiling is safe and feasible for saccular VA-PICA aneurysms. However, surgical clipping can be expected to benefit younger patients and/or cases of unfavorable morphology such as low aspect ratio. In addition, adverse angulation between aneurysm and parent artery can be another morphological factor for which an endovascular procedure is technically demanding.