Angiographically occult, progressively expanding, giant vertebral artery aneurysm. Case report

Hunterian ligation is a well-known treatment for complex aneurysms not amenable to direct microsurgical clip application. After proximal parent vessel occlusion, cerebral angiography is typically used to confirm aneurysm thrombosis. The authors report on a vertebral artery (VA) aneurysm that had progressively expanded and caused brainstem compression after hunterian ligation, despite nondiagnostic findings on both conventional and computed tomography (CT) angiography at multiple time points. This 64-year-old woman underwent hunterian ligation of a 1.8-cm VA aneurysm at the origin of the right posterior inferior cerebellar artery. An immediately postoperative conventional angiogram and follow-up CT angiograms obtained 5 and 6 years postligation confirmed complete obliteration of the lesion. Nine years after the initial surgery, however, the patient experienced neurological deterioration. Although CTs showed substantial aneurysm enlargement together with pontine compression, angiograms once again demonstrated complete right VA occlusion with no retrograde filling of the aneurysm. On reexploration, the aneurysm was effectively debulked, clipped, and obliterated. Arterial bleeding was found in the lesion neck, as was evidence of microrecanalization. Hunterian ligation for complex aneurysms carries the risk of microrecanalization and lesion expansion despite nondiagnostic angiography. Although this ligation procedure remains a viable treatment option in carefully selected patients, an extended follow-up evaluation period may be required even when imaging suggests aneurysm obliteration.