Encyclopædia Neurochirurgica
Malformation artério-veineuse cérébrale
*3. Individualizing the treatment
Although these classifications are very useful as a general guide, these grading systems are very rigid and often raise doubts when deciding on a therapeutic decision. The ideal situation is to treat the patient in a reference center for vascular neurosurgery with a multidisciplinary team, formed by a vascular and endovascular neurosurgeons and a radiosurgeon to analyze each case carefully and chose the best option for the patient.
Several factors should be considered in this decision-making process : 
Team experience ; AVM size : one of the most important factors for any possible treatment. Large and complex AVMs, as SM grades 4 and 5, are hard to treat and are associated to high morbi-mortality rates [95]. Depending on the AVM, the treatment risk is as high as or even higher than its natural history [93] ; Location : mainly if close to eloquent areas ; Angioarchitecture : diffuse nidus, single draining vein, deep venous drainage mean greater challenges in the treatment ; Patient age : due to the 2 to 4% annual risk of bleeding, young patients should be treated whenever possible to minimize the risk of intracerebral hemorrhage in their lifetime ; [7] Clinical conditions : patients with relevant comorbidities are not good candidates for microsurgical resection, and thus less invasive options should be considered, such as embolization and radiosurgery ; [52] Presence of symptoms : duration and seriousness, as well as functional impact in the patient’s quality of life, should be evaluated. Complex AVMs (SM 4 and 5) with installed relevant neurological deficits may eventually be treated by surgical resection because this option will not be associated to new relevant deficits as it would be in cases of asymptomatic patients, besides also preventing new episodes of hemorrhage. Previous bleeding : although not necessarily related to risk of rebleeding in the long term, can mean a greater risk of rebleeding in the short and mid-terms ; Patient’s profession : because some post-treatment deficits can be very morbid depending on the activity.