Subarachnoid hemorrhage caused by a dissecting aneurysm of the internal carotid artery

Object. Subarachnoid hemorrhage (SAH) caused by the rupture of a dissecting aneurysm of the internal carotid artery (ICA) has been considered rare. Based on data from cooperatively collected cases, the clinical features of patients with dissecting aneurysms of the ICA who presented with SAH were examined. Methods. Data from 18 patients with dissecting aneurysms of the ICA who presented with SAH diagnosed on the basis of clinical signs, neuroradiological findings, and intraoperative findings from 41 institutions were collected during a 5-year period between 1995 and 1999. The authors found that 0.3% of all cases of SAH and 3.1% of cases of SAH of unverified cause were attributable to a dissecting aneurysm of the ICA. Eleven patients (61%) were middle-aged women, and eight patients (44%) had hypertension. Rebleeding before admission was demonstrated in 13 patients (72%), and intraoperative bleeding was exhibited in half of the patients who underwent surgery during the acute stage. Postoperative growth of an aneurysm bulge or recurrent SAH was seen in five of 10 patients who had undergone wrapping or clipping of the aneurysm bulge in the acute phase. Trapping with or without bypass, which resulted in no postoperative recurrence, was performed in three patients in the acute stage and in two patients in the chronic stage. Twelve patients (67%) had a poor prognosis, primarily attributed to intraoperative bleeding and postoperative recurrence. Conclusions. Generally, dissecting aneurysms of the ICA are not thought of as frequent causes of SAH. Nonetheless, the presence of these aneurysms should be considered when dealing with SAH because they have a susceptibility to bleeding that can lead to a poor prognosis. Careful surgical planning is necessary to decrease intraoperative bleeding and to avoid postoperative recurrence.