Encyclopædia Neurochirurgica
Malformation artério-veineuse cérébrale
4.2. Endovascular treatment
The endovascular approach can be meant to cure the AVM or to make microsurgery or radiosurgery easier. Small AVMs can be cured through embolization alone, but big or giant AVMs can rarely be completely eliminated through the endovascular method.
Embolization can be made with : n-Butyl cyanoacrylate (NBCA) ; polyvinyl alcohol (PVA) ; ethylene vinyl alcohol copolymer (Onyx).
Embolization indications :
Patient prefers a non-invasive treatment and does not agree with neurosurgical intervention. Small AVMs with a single feeding artery : embolization alone, mainly when smaller than 1 cm [107]. Cortical AVMs bigger than 3 cm in diameter : embolization should be considered to make microsurgery easier, by reducing the volume of the nidus, occluding arteriovenous fistulas and deep feeding arteries, thus facilitating the surgery. Prior to radiosurgery, in order to treat risk factors of bleeding such as intranidal aneurysms that may cause bleeding during the period radiosurgical takes to cure. Shrink the size of the AVM, particularly at the periphery, to reduce the size of the radiation field required for treatment. This indication must be analyzed judiciously, because the endovascular cast may deform the AVM limits, jeopardizing the radiosurgical planning.
Advantages are : immediate reduction of the AVM blood flow, thus greatly reducing the chance of the intraoperative phenomenon known as “normal perfusion pressure breakthrough” [97], besides the reduction of the surgical time and of blood loss [35].
Disadvantages are : although considered a minimally invasive procedure, complications happen in 6 to 14% of the cases, most are not serious. However some serious complications have been reported, such as intravascular adherence of the microcatheter, hemorrhage during or right after the embolization (in up to 5% of the cases) cerebral ischemia by erratic embolization, and death. [20, 107] Another disadvantage are the reduction of the AVM “compressibility” during surgery, the endovascular cast may deform the AVM limits to radiosurgical planning, and some times the deep feeders are not occluded.
It is important to always keep in mind that embolization is an invasive method that associates morbidity and mortality to the treatment, and that serial procedures lead to greater risks.