Abstract
We have been employing preoperative embolization prior to microsurgical removal of cerebral arteriovenous malformations (AVMs) since 1988. In the present study, we analyzed the effects of preoperative embolization in a consecutive series of 24 cases of high-flow, large AVMs (>4cm in maximum diameter) treated between 1985 and 1991. We have chosen to use polyflilament polyester threads as an embolization material, because they cause minimal inflammatory reactions and no risks of venous occlusion. The threads were 200 micron in diameter and 5-10mm in length. We embolized 1 or 2 feeders each time until the mean feeder pressure rose to 70-90mmHg. This was repeated several times with an interval of 1-2 weeks. Microsurgical removal was performed within 1-2 weeks after the final embolization. In five cases, we encountered headache, deterioration of impaired consciousness or hemiparesis after embolization. However, all of these were transient. There was no major difference in location, age or initial symptoms between the group treated by microsurgical removal alone, and the group treated by combination of microsurgery and embolization. However, the AVMs operated after embolization were larger in volume than those treated by microsurgery alone. A classification of Spetzler and Martin also indicated that more difficult AVMs were treated by microsurgery with preoperative embolization. The total amount of blood loss was significantly small in cases operated after embolization in the group of very large AVMs (>20ml). Consequently, the operation time tended to be shorter in cases operated with embolization. Hyperemic complications were significantly less frequent in cases operated after embolization. Although there was no significant difference in overall outcome between these 2 groups, new deficits produced by microsurgical removal were significantly less frequent in cases operated after embolization. Earlier surgery after embolization appeared to be important to avoid recruitment and enlargement of small deep penetrating feeders. Polyfilament polyester threads are useful as an embolization material to make earlier surgery easier because of minimal inflammatory reactions and no risks of venous occlusion.
