What is the difference between a Cavernous Malformation (CM) and an Arteriovenous Malformation (AVM)?

From the Guidelines

Cavernomas and arteriovenous malformations (AVMs) are distinct vascular abnormalities with different clinical implications, and the most recent evidence suggests that AVMs have a higher risk of hemorrhage and require more complex interventions. The key difference between cavernomas and AVMs lies in their blood flow patterns, with cavernomas having slow flow without arterial feeders and AVMs having high-pressure, high-flow systems with identifiable feeding arteries and draining veins 1. Cavernomas typically present with seizures or focal neurological deficits from small hemorrhages or mass effect, whereas AVMs more commonly cause larger intracranial hemorrhages due to their high-pressure system.

Clinical Presentation and Imaging

On imaging, cavernomas appear as "popcorn" lesions with a rim of hemosiderin on MRI but are often not visible on angiography due to slow flow 1. AVMs show characteristic "flow voids" on MRI and are clearly visible on angiography with their feeding arteries and draining veins. The annual rupture risk of a brain AVM is 1.3% for previously unruptured AVM and up to 4.8% for previously ruptured lesions, highlighting the need for prompt treatment 1.

Treatment Approaches

Treatment approaches differ based on these characteristics, with cavernomas often managed conservatively or surgically removed if symptomatic, while AVMs may require more complex interventions including embolization, stereotactic radiosurgery, or surgical resection depending on their size and location. The ARUBA trial concluded that medical management alone was superior to medical management with interventional therapy for the prevention of death or stroke in patients with unruptured brain AVMs 1.

Key Considerations

Some key considerations in the management of AVMs include the risk of hemorrhage, the location and size of the lesion, and the patient's overall health status. Pediatric patients with AVMs are at higher risk of hemorrhage and may require more aggressive treatment, given their longer life expectancy and higher lifetime risk of hemorrhage 1. In summary, the management of cavernomas and AVMs requires a tailored approach based on the individual patient's characteristics and the specific features of the lesion, with a focus on minimizing the risk of morbidity, mortality, and improving quality of life.

From the Research

Cavernoma vs AVM: Key Differences

• Cavernomas are vascular lesions that consist of abnormally large capillary cavities without intervening neural tissue, whereas AVMs are anomalous direct shunts between cerebral arteries and veins that convalesce into a vascular nidus 2.
• The treatment strategies for AVMs are challenging and variable, including surgical resection, embolization, stereotactic radiosurgery (SRS), and observation, whereas cavernomas are often treated with microsurgical removal or SRS 2, 3.
• The risk of hemorrhage is a major concern in both cavernomas and AVMs, but the risk of hemorrhage is higher in AVMs, with an estimated cumulative lifetime hemorrhage risk of 2-4% per year 2, whereas cavernomas have an annual hemorrhage rate of 0.15-2.7% 4.

Treatment Outcomes

• SRS has been shown to be an effective treatment for cavernomas, with a complete response rate of 24.5% and a partial response rate of 60.2% 5.
• Microsurgical removal of cavernomas has been shown to be effective, with a perioperative morbidity rate of 29.2% and a long-term morbidity rate of 5.5% 3.
• Surgical treatment of AVMs has been shown to be effective, with a complete nidal obliteration rate of 80-90% 2.

Hemorrhage Risk

• Previous hemorrhage is a significant predictor of subsequent symptomatic hemorrhage in cavernomas, with a higher risk of symptomatic hemorrhage in follow-up than those without previous hemorrhage 4.
• The risk of hemorrhage in AVMs is higher than in cavernomas, with an estimated cumulative lifetime hemorrhage risk of 2-4% per year 2.
• The annual hemorrhage rate for cavernomas is 0.15-2.7%, whereas the annual hemorrhage rate for AVMs is not specified in the provided studies.

Seizure Outcome

• Patients with cavernoma-related epilepsy who underwent surgical treatment had better seizure outcomes than those who underwent conservative treatment, with 88% of patients in the surgical group being seizure-free for at least 2 years 6.
• The cumulative probability of staying seizure-free during a 5-year period was 73% for the surgical group, 22% for the conservative group, and 68% for the delayed surgical group 6.