Neurovascular Surgery Brain Aneurysm & AVM Center
Combined Modality Treatment in the Management of Brain Arteriovenous Malformations (AVM

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Cerebral AVMs are most commonly discovered in young adults aged 20-40 years. These lesions are usually detected in patients as the result of a seizure or hemorrhage. AVMs hemorrhage at a rate of 4% per year (ref. to Ondra). Approximately half of these hemorrhages will carry significant morbidity or mortality, therefore when one considers management of a young patient with a brain AVM, the lifetime risk of hemorrhage can be substantial.

Treatment of brain AVMs has been greatly enhanced by adopting a team approach utilizing combined modality therapy. Using this strategy, a treatment plan is devised to offer the lowest risk yet highest chance of obliterating the lesion. The three modalities of treatment currently available include endovascular introduction of agents which occlude parts or all of the AVM, standard microneurosurgical techniques to remove an AVM or radiosurgery (focused radiation). Currently available endovascular techniques involve passing tiny catheters into the cerebral vessels feeding the AVM. Once the catheter reaches the nidus of the AVM, a glue material can be injected to occlude portions, or in some cases all, of the arteriovenous malformation. The endovascular technique carries a risk of 3-5% of serious complication, however it can make subsequent surgical removal of an AVM significantly safer, or can reduce the size of an AVM to a volume where radiosurgery carries a higher efficacy.

Figure 1 shows a brain AVM prior to and after glue embolization of a portion of the AVM in the parietal region in a young patient who presented with seizures. Subsequent surgical resection of this lesion was greatly aided by the preoperative embolization (Figure 2). Approximately 5-10% of AVMs can be cured (completely obliterated on angiography) using endovascular techniques. If flow still persists through a portion of the AVM after embolization, the patient remains at risk for future hemorrhage. In patients where embolization is used prior to surgery, the subsequent operation is made significantly easier than if the embolization had not been performed. The operating time can be reduced, as can the intraoperative blood loss during the resection of these sometimes treacherous lesions. At times, embolization techniques with partial obliteration of an AVM are used as a palliative maneuver. Patients with significant edema or a steal syndrome due to the AVM can be helped with partial obliteration of the lesion. Although this does not protect the patient from subsequent hemorrhage, it will often help alleviate neurologic symptoms and allow the patient to live a normal life.

If the AVM is reduced in size significantly, the lesion may then be amenable to techniques of stereotactic radiosurgery where a focused beam of radiation is used at a one-time treatment. This radiation causes changes in the blood vessel walls, and over the course of 2-3 years the AVM can obliterate on angiography. This technique is most effective in smaller lesions (diameter less than 2.5 cm). Obliteration rates of up to 85% have been reported by two years after treatment. The risk of injury to surrounding normal brain tissue is dependent upon the dose of radiation used. This risk can usually be kept to less than 3-4% chance of injury to surrounding brain tissue.

The decision of whether or not to treat a given brain AVM depends on its location and the extent of anticipated possible deficit associated with treatment. These risks must be weighed against the risk of the natural history of the untreated lesion. If treatment can be offered with a risk significantly lower than the natural history of the disease, then treatment should proceed. Treatment of a brain AVM has been greatly facilitated by the team approach. Neurologists, interventional neuroradiologists, and neurosurgeons all work together to define the potential risks of treatment and of the natural history of a patient with a given AVM. It is hoped that by utilizing such a team approach, safer treatment for these lesions can be obtained.

Figure 1: AP angiograms demonstrate a large arteriovenous malformation of the left parietal region. The film on the left demonstrates the feeding arteries from the middle cerebral artery system with a large draining vein medially to the sagittal sinus. The film on the right demonstrates several large feeding vessels from the posterior cerebral artery on the left side.

Figure 2: The AVM of the patient shown in Figure 1 after endovascular embolization using N-butyl-cyanoacryalate glue for part of the AVM. As can be seen, the AP angiogram on the carotid circulation (left) shows a greatly diminished arterial to venous shunt. As well, the film of the right demonstrates decreased filling from the posterior cerebral supply to the AVM.

Figure 3: AP angiograms following surgical resection of the large AVM of the patient shown in Figures 1 and 2. Preoperative embolization made the operation safer with a minimum of blood loss at the time of operation. As can be seen on the carotid injection (left film). there is no arterial to venous shunting. The vertebral injection (right film) shows no AV shunting. The patient made an excellent recovery from surgery with no neurologic deficits.

1. Ondra SL, Troupp H, George ED, Schwab K: The natural history of symptomatic arteriovenous malformations of the brain: A 24 year follow-up assessment. J Neurosurg 73:387-391, 1990.