Arteriovenous Malformations Treatment & Management

Treatment planning for arteriovenous malformations (AVMs) depends on risk of subsequent hemorrhage, which is determined by the demographic, historical, and angiographic features of the individual patient as discussed above. Prior hemorrhage, smaller AVM size, deep venous drainage, and relatively high arterial feeding pressures make subsequent hemorrhage more likely.

No randomized clinical trial comparing invasive treatment (staged embolization followed by either neurosurgical resection or radiosurgery) versus medical management alone of patients with a known brain AVM is available. There is little disagreement that patients with an AVM-related hemorrhage need treatment to avoid subsequent hemorrhages given the high recurrent hemorrhage rates. However, until recently, most patients with a diagnosis of an unruptured brain AVM were also considered candidates for invasive treatment to prevent a devastating hemorrhage. This concept has been challenged because of the low annual hemorrhage rates in patients who did not present with a brain hemorrhage.

To answer this question, the NIH-sponsored, multicenter Unruptured Brain Arteriovenous Malformations Trial (ARUBA) is conducted in the United States, Canada, Europe, and Australia. ^{[11, 12]} A total of 800 patients will be randomly assigned in 90 centers to invasive therapy (endovascular, surgical, and/or radiation therapy) versus medical management alone. Patients will be followed for a minimum of 5 years and a maximum of 7.5 years (mean, 6.25 y) from randomization. Final study results will not be available until 2012.

Until the ARUBA study results are available, treatment is recommended for the younger patient with one or more of the high-risk features for an AVM rupture, whereas an older individual or a patient with no high-risk features may be best treated by managing the medical aspects of the illness alone. In such patients, anticonvulsants for seizure control and appropriate analgesia for headaches may be the only treatment recommendations necessary.

• Anticonvulsants

  • Standard anticonvulsant therapy, pursuant to the type of seizure, is generally sufficient to bring seizures under control.

  • In many patients, seizures are well controlled with phenytoin, carbamazepine, valproic acid, or lamotrigine or other antiepileptic drugs indicated for partial onset seizures. Please see the article Complex Partial Seizures.

  • Individuals with cerebral AVMs are at a moderately higher risk for seizures; risk depends on the location of the AVM and the history of intracranial hemorrhage or focal neurologic deficit. No evidence suggests the use of antiepileptic medications for prophylaxis of individuals who have an AVM but have never had a seizure.

• Headache management

  • Headache of acute onset without localizing neurological signs may be the presenting sign of a hemorrhage, either intraventricular or subarachnoidal, and need immediate assessment by neuroimaging.

  • For AVM-associated headaches that are not associated with an intracranial hemorrhage, standard analgesia for headache may be used, either nonspecific or migraine specific. Serotonin agonists are not specifically contraindicated, unless focal neurological symptoms appear as a part of the migraine. Please see the article Migraine Headache.

Invasive treatment of arteriovenous malformations (AVMs) may include endovascular embolization, surgical resection, and focal beam radiation, alone or in any combination. ^[13] The surgical treatment risk has traditionally been estimated by the Spetzler-Martin grading scale, which includes grades I-V. This grading system assigns 1 point to AVMs smaller than 3 cm in largest diameter, 2 points to AVMs between 3 and 6 cm in largest diameter, and 3 points for AVMs larger than 6 cm. A further point is added if the AVM is located in functionally critical brain (eg, language, motor, sensory, or visual cortex), and another point if the AVM has a deep venous drainage.

The current American Heart Association multidisciplinary management guidelines for the treatment of brain AVMs recommend the following approach: ^[3]

1. Surgical extirpation is strongly suggested as the primary treatment for Spetzler-Martin grade I and II if surgically accessible with low risk.

2. Radiation therapy alone is recommended for Spetzler-Martin grade I or II if the AVM is less than 3 cm in size and surgery has an increased surgical risk based on location and vascular anatomy.

3. Brain AVM of Spetzler-Martin grades III can often be treated by a multimodal approach with embolization followed by surgical extirpation. If the lesion has a high surgical risk based on location and vascular anatomy, radiation therapy may be performed after embolization.

4. AVMs of Spetzler-Martin grade IV and V are often not amenable to surgical treatment alone because of the high procedural risk. These AVMs can be approached by a combined multimodal approach of a combination of embolization, radiosurgery, and/or surgery.

5. In general, embolization should only be performed if the goal is complete AVM eradication with other treatment modalities. The only exception is palliative embolization in patients with an AVM of Spetzler-Martin grade IV or V with venous outflow obstruction or true steal phenomenon in order to reduce arterial inflow to control edema or to reduce the amount of shunt, respectively.

A recent supplementary grading system used patient age, hemorrhagic presentation, nidal diffuseness, and deep perforating artery supply when selecting patients with brain AVMs for surgery. When used along with the Spetzler-Martin grading system, this grading system has been shown to have higher predictive accuracy, improving preoperative risk prediction and patient selection for surgery. ^[14]

Surgical resection

Surgical resection is the mainstay of definitive treatment and is most effective with more easily accessible lesions of smaller size. ^[15]

AVMs may be approached with craniotomy over the cerebral convexity, via the skull base, or via the ventricular system.

Arterial feeders are isolated and ligated. Then the nidus is resected. The draining veins are ligated last so that the pressure is not increased while the nidus is being resected. Arterial aneurysms may be clipped surgically as well. Intranidal aneurysms are resected with the AVM. Distal aneurysms are usually flow related and resolve when the AVM is resected.

Postsurgical angiography is done routinely to ensure that no residual AVM exists; however, cases of reappearance of AVMs, years after a negative postresection angiogram, have been reported.

Endovascular embolization

Superselective endovascular treatment includes delivery of thrombosing agents such as quick-acting acrylate glue (N -butyl cyanoacrylate [NBCA]), thrombus-inducing coils, Onyx liquid embolic fluid, or small balloons into the AVM nidus.

The goal of embolization is to block the high-velocity shunting of blood from the high-pressure arterial system into the venous system. Serial embolization sessions may whittle the AVM down to a fraction of its original size; the reduced AVM size and the presence of embolic material within the AVM make surgery and radiosurgery safer and more accurate. However, embolization can increase the pressure inside the nidus of the AVM due to the changes in blood flow and increases the rupture risk in the short term. Thus, if surgery is anticipated, it is usually scheduled 1-2 days after embolization. Embolization may be used to produce relief of neurologic symptoms caused by a large lesion, even if the goal of treatment is not complete obliteration. In most cases, embolization alone is not sufficient to completely obliterate the AVM. However, isolated case series have reported 11-40% of AVM obliteration with only endovascular embolization.

Embolization may be performed in a single-stage versus multistage approach. Although most literature support the use of the multistage approach, a retrospective study supports the safety and effectiveness of the aggressive single-stage embolization. ^[16] The single-stage approach has the inherent benefit of reducing the overall under treatment time reducing the intertreatment bleeding risk and brain AVM collateral reconstitution.

Radiosurgery

Radiosurgery is an option that is generally used to treat AVMs that are approximately 3 cm in diameter or less. Proton beam, linear accelerator, or gamma knife methods are used to deliver a high dose of radiation to the AVM, while minimizing the effects to surrounding brain tissue; a single dose generally is given. However, staged radiosurgery procedures are being used more frequently to treat symptomatic large AVMs in conjunction with embolization. During embolization, keep in mind if the patient is going to undergo radiosurgery, since patchy embolization of an AVM can make radiosurgery even more difficult. Radiotherapy is thought to work by inducing thrombosis. This approach is appealing because of its apparent noninvasiveness.

During the period after radiosurgery, the vessels are thrombosing and those AVMs that have ruptured are at a higher risk of rehemorrhage during that time. A single-center observational study from Spain has shown that radiosurgical therapy gradually decreases the long-term bleeding rates of both hemorrhagic and nonhemorrhagic AVM. ^[17]

MRI often shows high signal in surrounding brain white matter following treatment; actual mass effect from edema can be seen when larger territories are covered. Radiosurgery may take 1-3 years to achieve thrombosis of an AVM, thus the patient remains at risk for hemorrhage from AVM during the treatment period.

Combined radiosurgery and embolization

Controversies are noted in regard to the sequence of combined treatment commonly advocated to treat large AVMs. Kano et al reported their experience with stereotactic radiosurgery in patients harboring AVMs who had undergone prior embolization. Using a case-control matched approach, the authors determined that previously embolized AVMs have a lower rate of obliteration after SRS. This finding mirrors reports by other groups. ^[18] A long-term follow-up review is needed to determine the precise effects of partial or complete embolization on rebleeding, on seizures, and on progressive neurological deficits. ^[19] A systematic study of outcomes is needed so as to determine the best combination of approaches for such patients.

Treatment of arteriovenous malformations (AVMs) is best achieved with a multispecialty team comprising a neurologist, neuropsychologist, neurosurgeon, interventional neuroradiologist, and neuroanesthesiologist.

No particular activity restrictions are placed on patients with arteriovenous malformations (AVMs), besides the usual postsurgical care.

AVM patients with seizures should follow the same protocols as patients with epilepsy without AVM.