Ruptured irregularly shaped aneurysms: pseudoaneurysm formation in a thrombus located at the rupture site

Object. The authors describe the clinical, radiological, and pathological f indings of ruptured cerebral aneurysms with irregular configurations. Methods. Eight patients with subarachnoid hemorrhage due to ruptured irregu larly shaped aneurysms were examined. The preoperative radiological finding s in these cases were compared with the pathological and operative findings of endovascular or open surgery. All of the aneurysms exhibited delayed opacification and delayed washout of contrast medium from the irregularly shaped portion of the aneurysm on dig ital subtraction angiography and/or helical computerized tomography scannin g. Endovascular embolization with platinum coils was attempted in the first four patients who underwent treatment. In three of these patients the aneu rysm ruptured again during the endovascular procedure. In the fourth patien t an intraaneurysm thrombus was observed during the procedure and clipping was performed. In the subsequent four patients, three underwent clipping wi thout complication and one underwent partial aneurysm embolization because of poor general status. A thrombus adjacent to the aneurysm dome was observ ed in the patients who underwent open surgery. Pathological examination of the operative specimens revealed a pseudoaneurysm-like cavity in the thromb us that was adherent to the aneurysm. Conclusions. Ruptured irregularly shaped aneurysms may be accompanied by fr agile pseudoaneurysm-like cavities located at the rupture point. Because th ese aneurysms have a high risk of repeated rupture during an endovascular p rocedure, advancing microinstruments to the weaker portion of the aneurysm should be avoided.