BLOOD BLISTERLIKE ANEURYSMS OF THE INTERNAL CAROTID-ARTERY

Object. An aneurysm arising from the anterior wall of the internal car otid artery (ICA) is a poorly understood entity. A small hemispherical bulge from the anterior wall of the ICA, which is called a ''blood bl isterlike aneurysm'' (BBA), may be confused with a tiny berry aneurysm although the clinical features are distinctly different. This paper s ummarizes the clinical course of patients with this lesion to clarify the nature of the BBA. Methods. Six patients with BBAs who presented w ith subarachnoid hemorrhage (SAH) are described. In all patients, the initial angiogram obtained soon after SAH showed only a small bulge fr om the anterior wall of the ICA. In three of the six patients this bul ge had progressed to a saccular appearance within a few weeks. The wal l of the lesion was so thin and fragile that the aneurysm ruptured at the base during clipping or within a few hours after clipping in two p atients. Conclusions. From the authors' experience, as well as a revie w of the literature, which includes an autopsy study of similar cases, it is inferred that these lesions are focal wall defects covered only with thin fibrous tissue and that they are therefore not true aneurys ms. Direct clipping often causes laceration of the lesion, whereas com plete wrapping or clipping after wrapping is effective, but may fail t o prevent growth of the aneurysm. Endovascular occlusion of the cervic al ICA with or without bypass surgery, which is less risky than direct surgery, is another option.