Aneurysms of spinal arteries associated with intramedullary arteriovenous malformations. I. Angiographic and clinical aspects.

PURPOSE To evaluate the nature of aneurysms of the spinal arteries, their relative frequency, and the risks associated with these lesions.

METHODS We retrospectively reviewed the spinal angiographic studies of 186 patients with spinal cord vascular malformations--70 intramedullary AVMs, 44 extra (peri) medullary AV fistulas, and 72 dural AV fistulas.

RESULTS Fifteen spinal artery aneurysms (SAs) in 14 out of 70 patients (20%) with an intramedullary AVM were discovered. No SAs were observed in the other types of spinal vascular malformations. The intramedullary AVMs with SAs were cervical in seven cases and thoracic in the other seven cases (one of the thoracic had two SAs). Fourteen SAs were located on a major feeding vessel to the associated intramedullary AVM (10 on the anterior spinal artery and four on a posterior spinal artery and only one SA was located remote from the AVM feeding vessels. This remote aneurysm was located on the intercostal artery feeding a vertebral angioma in a patient with metameric angiomatosis. Subarachnoid hemorrhage occurred in all cases of SA. The presence of a SA carried a statistically significant (P less than .05) increase in the risk of bleeding.

CONCLUSIONS Although increased blood flow seems to be an important factor in formation of these SAs associated with intramedullary AVMs, the role of a developmental vascular anomaly must be stressed: metameric angiomatosis was found in six out of the 14 patients (43%).