Brain AVMs
The decision to treat brain arteriovenous malformations depends on the symptoms that they cause (such as seizures or headaches). The bleeding risk is predicted by previous episodes of hemorrhage, and whether on the CTA or MRA scan the AVM appears to be deep-seated or have deep venous drainage. Size of the AVM and the presence of aneurysms appears to matter less. In HHT, some lesions (high-flow arteriovenous fistulae) tend to cause more problems, and treatment is warranted. Other AVMs may regress over time without intervention. Various modalities are available, depending on the location of the AVM and its size: surgery, radiation-based treatment and embolization. Sometimes, multiple modalities are used on the same lesion.Surgery (by craniotomy, open brain surgery) may be offered based on the risks of treatment as determined by the Spetzler–Martin scale (grade I-V); this score is higher in larger lesions that are close to important brain structures and have deep venous drainage. High grade lesions (IV and V) have an unacceptably high risk and surgery is not typically offered in those cases. Radiosurgery (using targeted radiation therapy such as by a gamma knife) may be used if the lesion is small but close to vital structures. Finally, embolization may be used on small lesions that have only a single feeding vessel. Experimental treatments
Several anti-angiogenesis drugs approved for other conditions, such as cancer, have been investigated in small clinical trials. The anti-VEGF antibody bevacizumab, for instance, has been used off-label in several studies.
Surgical excision has now essentially been abandoned due to the success of embolotherapy.Those with either definite pulmonary AVMs or an abnormal contrast echocardiogram with no clearly visible lesions are deemed to be at risk from brain emboli. They are therefore counselled to avoid scuba diving, during which small air bubbles may form in the bloodstream that may migrate to the brain and cause stroke. Similarly, antimicrobial prophylaxis is advised during procedures in which bacteria may enter the bloodstream, such as dental work, and avoidance of air bubbles during intravenous therapy. Liver AVMs
Given that liver AVMs generally cause high-output cardiac failure, the emphasis is on treating this with diuretics to reduce the circulating blood volume, restriction of salt and fluid intake, and antiarrhythmic agents in case of irregular heart beat. This may be sufficient in treating the symptoms of swelling and breathlessness. If this treatment is not effective or leads to side effects or complications, the only remaining option is liver transplantation. This is reserved for those with severe symptoms, as it carries a mortality of about 10%, but leads to good results if successful. The exact point at which liver transplantion is to be offered is not yet completely established. Embolization treatment has been attempted, but leads to severe complications in a proportion of patients and is discouraged.Other liver-related complications (portal hypertension, esophageal varices, ascites, hepatic encephalopathy) are treated with the same modalities as used in cirrhosis, although the use of transjugular intrahepatic portosystemic shunt treatment is discouraged due to the lack of documented benefit.