This is a correspondence from
Darren Orbach, MD PhD
Division Chief, Interventional & Neurointerventional Radiology
Children’s Hospital Boston / Harvard Medical School
300 Longwood Avenue
Boston, MA 02115
Hi Mr. Christou,
Thanks for your email. As someone who treats both brain/spine AVMs and extracranial AVMs, I would certainly concur with your assessment that in some ways treating the peripheral lesions can be more challenging than treating the brain lesions. In particular, with most brain AVMs we treat, we think in terms of cure – i.e. getting the patient to a state whereby the risk of the AVM posing a clinical challenge to the patient is minimal. Unfortunately, it is only for the tiniest minority of peripheral AVMs that we can talk of cure in this way – for the vast majority, our goal is to control symptoms and minimize the impact of the AVM on the patient’s day-to-day life. Part of this distinction is due to the fact that brain AVMs pose an ongoing risk to the patient’s life, in a way that is rarely true for peripheral AVMs, so the treatment approaches that have developed through the years for brain AVMs have been oriented towards cure, whenever possible for many years. But a big part of the reason for the distinction is technical – brain AVMs are more distinct from their surrounding tissue, both in their microarchitecture, and visually to the surgeon, than are peripheral AVMs.
Thus, my neurosurgical colleagues who resect brain tumors that I have embolized usually have little trouble distinguishing AVM from brain tissue. In contrast, for the few patients we send to the OR to have the plastic surgeons resect their peripheral AVMs, it is rarely easy, or even possible, to distinguish where in the soft tissue the AVM ends and the normal muscle or fat tissue begins.
Because of this distinction, our approach towards peripheral AVMs is to treat them when they are symptomatic. Most often, this is by way of embolization. I do happen to use Onyx a great deal, both in the CNS and in the periphery, and tend to favor it because of the exquisite control it offers the operator in terms of target deposition. However, Onyx is a tool just like the other liquid embolic agents, and I’m not convinced that using it really changes the natural history of peripheral AVMs (or at least, I’ll readily admit the that the jury is still out). I have not found the black color of Onyx to be problematic, as most AVMs are sufficiently below the skin surface that there is at most minimal discoloration – when visible at all, the appearance is similar to the blueish appearance of a vein under the skin. In cases where Onyx is likely to cause significant discoloration, the lesion itself is so superficial, that the skin has already darkened significantly. I have had a few cases where I was concerned enough about discoloration that I used n-BCA rather than Onyx, but these are the exception.
There is certainly a lot of research ongoing with regard to pharmacological approaches to AVM, and given the pretty rapid development of our understanding of the underlying vascular biology, I’m confident that 10 years from now, we will have far superior active agents to offer our patients, either by mouth or by directed infusions into the lesion. For cases on which we at the Children’s Vascular Anomalies Center are consulted, where there is a lesion that is both dangerous and that cannot be managed by standard means, we do offer trials of angiogenesis-inhibiting medications.
However, these are still early in their development and have no accompanying long-term data with regard to efficacy and safety, and are not something to which we would point patients whose lesions can be better managed by more standard approaches.
I hope all this helps, and best of luck to you and your daughter.