Long-term histopathology of intracranial aneurysms after endovascular treatment with coils. Report of two cases with ultrastructural evaluations by scanning electron microscopy.

We describe the results of electron microscopic examination in two patients with ruptured intracranial aneurysms who were successfully treated by endovascular coil embolization. The aneurysms were seen completely occluded on the follow-up angiograms. Autopsies of these patients were performed five and 26 months after endovascular treatment when they died of pneumonia and thalamic hemorrhage, respectively. The aneurysms were densely filled with the coils, which were readily identified through the thin and transparent wall of the aneurysmal dome. The orifice of the aneurysm was completely occluded so that macroscopically the coils were not directly visualized through the orifice. To examine any evidence of endothelialization across the orifice of the aneurysms, scanning electron microscopic examination was performed. In both cases, evidence of well regenerative endothelialization was observed across the aneurysmal orifice, being contiguous with the endothelial layer of the adjacent parent vessels. These ultrastructural findings indicate that the aneurysms are completely isolated from the lumen of the parent artery by a continuous lining of the regenerated endothelial cells following the endo vascular treatment with coils, and further suggest that aneurysms have a potential of being cured permanently by this treatment modality. This is, to the best of our knowledge, the first report in humans verifying a complete endothelialization of the luminal surface at the aneurysmal neck after coil embolization, as evidenced by scanning electron microscopy.