In August, the American Heart Association/American Stroke Association (AHA/ASA) released an update on brain arteriovenous malformations (AVMs) in the form of a new scientific statement. Lead author of the Management of Brain Arteriovenous Malformations: A Scientific Statement for Healthcare Professionals, Colin Derdeyn (University of Iowa, Carver College of Medicine, Iowa City, USA) now provides the top ten takeaways.
A brief review of the current state and goals of the American Heart Association/American Stroke Association (AHA/ASA) guidelines and scientific statements is in order. These documents are developed in support of the AHA/ASA mission to reduce death and disability from stroke. The rigor and methodology for these two vehicles for transmitting knowledge have changed recently. Guidelines are intended to provide evidence-based recommendations for diagnosis and management and must now include evidence tables to support these recommendations. These are large, broad scope projects. There are six core guidelines that are revisited every three years. These include Management of Ischaemic Stroke, Spontaneous Intracerebral Haemorrhage, Subarachnoid Haemorrhage, Primary Stroke Prevention, Secondary Stroke Prevention, and Stroke Recovery and Rehabilitation. Scientific statements are smaller and more focused. These are intended to summarise knowledge in more focused areas and identify those that need more information. The recent brain arteriovenous malformation (bAVM) statement fell into the latter category. This is appropriate owing to the lack of high-quality evidence in this area.
The primary reason for the bAVM statement was to synthesise advances in the field and identify areas needing more work since the prior AHA/ASA statement published in 2001. This included new data related to epidemiology, biology, imaging, outcomes with treatment and the introduction of new embolic agents. Most notable of these data are the results of the first randomised trial of intervention for unruptured bAVMs, the ARUBA (A randomized trial of unruptured brain arteriovenous malformations) trial.
1.) bAVMs are often acquired lesions. The past decade has seen great advances in our understanding of vascular biology and the genetic and environmental factors involved in bAVM formation and growth. Research in this area may lead to the development of medical interventions that may stabilise or prevent bAVM growth.
2.) We have a much better, but still incomplete, handle on the natural history of patients with unruptured bAVMs (at least out to 10 years). The annual risk (over a 10-year horizon) for first-ever haemorrhage for patients with an unruptured bAVM is approximately 1%. The five-year risk for a first seizure for patients with unruptured bAVMs is 8%, and 58% of patients that have a first ever seizure develop epilepsy. Long-term, prospective, inclusive, population-based studies with complete follow-up are required to better define these long-term risks.
3.) Anatomic and clinical factors associated with rupture for patients with unruptured bAVMs are deep location, exclusively venous drainage, and associated aneurysms. These data come from prospective studies of AVM rupture risk, rather than comparisons of features of ruptured versus unruptured bAVMs, and are therefore more robust.
4.) Information guiding treatment decisions for patients with unruptured bAVMs remains limited. The one randomised trial of intervention (surgical, radiosurgical and/or embolisation) versus conservative therapy (ARUBA) for patients with unruptured bAVMs found worse outcomes with intervention after a mean follow up of 33 months (30.7% vs. 10.1% risk of stroke and death, respectively). Longer term follow up of these patients is important, as well as further randomised trials in this population. Better, prospective data on the relative risks and benefits of each of the individual interventions (surgical, radiosurgical and/or embolisation), and their combinations, is critically needed. This information could come from registries.
5.) The annual risk for re-rupture for patients with a ruptured bAVM is approximately 5% per year. This number comes from aggregations of large case series and is useful for guiding treatment decisions in this population.
6.) The Spetzler-Martin grading scale and subsequent modifications with the supplemental Lawton-Young scoring scale provide a well validated tool to predict risks from microsurgical bAVM resection. This is very useful for counselling patients with treatment options.
7.) Embolisation for bAVMS is increasingly done in an attempt for cure, but the risks and long term durability remain to be determined. Newer liquid agents have opened up this opportunity.
8.) Embolisation prior to radiosurgery for nidal volume reduction may reduce the efficacy of stereotactic radiosurgery. These data come from case series, not randomised trials, and if the association is real the mechanism is not clear. Possible biologic mechanisms or difficulty accurately targeting after embolisation are both possible.
9.) Complete AVM obliteration (surgical or stereotactic radiosurgery) likely reduces the risk of seizures.
10.) We need more data for treatment outcomes. The past 15 years have seen a tremendous growth in our knowledge of the biology and genetics of bAVMs. We have a much better understanding of the natural history of unruptured bAVMs. In addition, new endovascular agents have been introduced, as well as advances in our experience with stereotactic radiosurgery and microsurgery. The first randomised trial of treatment versus conservative management for unruptured bAVMs was also completed. Nevertheless, we still lack compelling evidence for many of the treatment decisions that are routinely made for patients with ruptured and unruptured bAVMs. The results of ARUBA point to a need for a better understanding of the risks of different treatment options, longer term follow up of untreated patients, and further randomised controlled trials to investigate the remaining therapeutic uncertainties.
Colin Derdeyn is chair and department executive officer of the Division of Radiology, University of Iowa, Carver College of Medicine, Iowa City, USA