Observation for Arteriovenous Malformation
Arteriovenous malformations (AVMs) are primarily treated with open surgery, endovascular therapy, or stereotactic radiosurgery (radiation). The goal of these treatment options is to obliterate the AVM and prevent it from hemorrhaging into the brain and causing a neurologic deficit.
However, in some cases, these obliterative treatment may not be possible. Instead, a conservative approach can be best. This involves observing the AVM over time with periodic monitoring. In this blog, we will discuss when an observation strategy may be taken and what you can expect from this treatment path.
When Would Conservative Management Be Necessary?
The goal of treatment for AVMs is to reduce the risk of brain hemorrhage from AVM rupture. Brain damage can occur because of spontaneous AVM hemorrhage but can also occur as a complication of surgical intervention. Therefore, it is important to weigh the risks of hemorrhage against the risks of surgical treatment to determine whether conservative management is right for you.
Risks of Hemorrhage
Assuming an annual AVM hemorrhage rate of 2 – 4% and an average life expectancy of 70 years, the cumulative AVM rupture risk can be calculated with this formula: 105 – age. For example, an individual who is 33 years old is estimated to have a cumulative AVM rupture risk of 72%, meaning that there is a 72% chance that the AVM will bleed in their lifetime. This formula estimates the upper limits for the risk of AVM rupture and the true risk of rupture may be slightly less.
Although convenient, this formula also does not consider the fact that the risk of AVM hemorrhage may change over time. The AVM hemorrhage rate may also be higher among the patients with prior rupture, AVM-associated aneurysms, lesions located in deep locations, and those with single venous drainage.
Some studies estimate a mortality rate of up to 10% associated with an AVM hemorrhage, with nearly 30 – 50% of patients sustaining neurologic deficits. AVM rupture is thus a devastating and life-threatening situation that requires immediate medical attention.
Risks of Treatment
Prediction of treatment risk is based on the characteristics of individual AVMs, such as their size, location, and the types of blood vessels involved. In low-grade AVMs, AVMs are smaller and/or located closer to the surface of the brain. This makes surgery easier and safer, leading to high cure rates and good postoperative outcomes.
In contrast, high-grade AVMs are larger and located more deeply in the brain. In these cases, surgery can be risky and lead to neurological complications. Nearly 50% of patients with grade V AVMs had a worse neurological outcome after surgery, whereas over 90% of patients with grade I AVMs experienced stable or improved neurological outcomes after surgery.
Whether to proceed with conservative management considers many factors such as patient age and AVM grade. For older patients with a low cumulative risk of AVM rupture and a high AVM grade, conservative management is favorable. In younger patients with a high cumulative risk of AVM rupture and a low AVM grade, surgery is likely to be of most benefit.
Each individual case is unique and requires a comprehensive evaluation from a neurosurgical team. Surgical treatment of an AVM is one of the most technically challenging operations in neurosurgery. Choosing the right neurosurgeon and team will be critical, even if you do not proceed with surgery, to weigh the risks and benefits appropriately throughout your care.
What Can I Expect From Conservative Management?
During conservative management, patients typically undergo MRI imaging every 3 to 5 years until the age of 65, or earlier if symptoms occur. During an MRI, patients lie still on a bed which will move into the scanner headfirst. The scan can take 30 minutes to an hour and patients will go home the same day.
These periodic MRI tests can help to identify bleeding that may have occurred without the patient knowing. Since a history of a bleed increases the risk of a future bleed, the presence of a “silent hemorrhage” may alter the course of treatment. If a silent hemorrhage is found, treatment options such as surgery, endovascular embolization, or radiosurgery may be considered.
- The decision to pursue conservative management is based on the risks of rupture versus the risks of treatment.
- In cases where surgery is deemed too risky and/or AVM rupture risk is low, conservative management may be favorable.