Surgical treatment of AVMs

Arteriovenous malformations (AVMs) are high-flow vascular anomalies characterized by a direct connection between arteries and veins, bypassing the capillary bed. This abnormal shunting results in turbulent blood flow, progressive lesion enlargement, and a range of clinical symptoms—from cosmetic disfigurement to life-threatening bleeding or cardiac overload.

Unlike low-flow vascular malformations, AVMs are aggressive, infiltrative, and often progressive if untreated. AVMs are frequently encountered at the stage of misdiagnosis, mismanagement, or post-complication. While embolization is a cornerstone of treatment, surgery plays a crucial role in achieving definitive control, particularly in cases where complete excision is possible. 

Surgery for arteriovenous malformations (AVMs) is a technically demanding procedure, requiring meticulous preoperative planning and execution, as well as specialized training. 

Indications for Surgical Treatment

Surgical excision of AVMs is considered in selected cases, often in combination with preoperative embolization. Indications include:

1. Life-Threatening Hemorrhage

• AVMs with ulceration, trauma, or spontaneous bleeding may require urgent surgical control.

• In some cases, partial excision or ligation of feeding vessels may be lifesaving, even if complete resection is not feasible at the time.

2. Functional Impairment or Risk to Vital Structures

• AVMs involving the face, extremities, airway, or urogenital tract may disrupt vision, breathing, speech, or continence.

• Surgery may restore or preserve function when non-surgical methods are inadequate.

3. Localized, Well-Demarcated Lesions

• Rare in AVMs, but when present, they are ideal for complete surgical excision.

• These offer the best outcomes with the lowest recurrence risk, particularly if embolized immediately before resection.

4. Debulking for Mass Effect or Disfigurement

• In large, infiltrative AVMs, partial surgical debulking may relieve pain, reduce deformity, or improve quality of life, even when cure is not possible.

5. Refractory to Embolization or Recurrence

• AVMs often recur after embolization alone due to collateral revascularization or an inadequate embolization technique.

• Surgery may be necessary when embolization fails to provide symptom relief or hemodynamic control.

Preoperative Planning

Before surgery is even considered, several critical steps are required:

a. Imaging

• MRI with MR angiography: Essential for assessing lesion extent, tissue involvement, and surrounding anatomy.

• Digital Subtraction Angiography (DSA): Often used in interventional planning to identify feeding arteries, shunting zones (the nidus), and venous drainage.

b. Multidisciplinary Evaluation

• AVM management should involve a vascular anomalies team, including:

  • Interventional radiologist

  • ENT, Maxillofacial, Neurosurgeon, Plastic surgeon (depending on location)

  • Hematologist (for coagulopathy risk)

  • Anesthesiologist familiar with high-blood-loss surgery

c. Preoperative Embolization

• Embolization is often performed 24–72 hours before surgery to reduce intraoperative bleeding.

• The goal is to occlude the abnormal vascular bed to minimize the risk of bleeding.

Surgical Techniques

a. Complete Resection

• The ideal surgical goal is complete resection of the AVM, including the nidus (the abnormal shunting core).

• This offers the best chance at long-term control or cure, but is only feasible in localized AVMs.

• Performed via meticulous dissection, often with intraoperative imaging and nerve monitoring.

b. Staged Resections

• For extensive or high-risk lesions, surgery may be staged to reduce blood loss and preserve function.

• Particularly common in large facial or extremity AVMs.

c. Debulking Surgery

• When complete excision is not possible, debulking can relieve:

  • Pain

  • Swelling

  • Tissue distortion or ulceration

• These procedures are palliative, not curative, and recurrence is expected.

d. Emergency Surgery

• In cases of acute bleeding or necrosis, ligating the feeding vessels or performing partial excision may be lifesaving.

• These are temporizing measures, often followed by definitive embolization treatment later.

Surgical treatment of arteriovenous malformations (AVMs) offers the possibility of definitive control in carefully selected cases. The nature of AVMs — infiltrative, high-flow, and prone to recurrence — means that both success and complications depend on anatomy, completeness of resection, and the experience of the multidisciplinary team.

Surgical Outcomes

a. Curative Potential

• Complete surgical resection (with nidus removal) offers the best chance of cure.

• This is typically possible for localized, well-defined AVMs and often requires preoperative embolization to achieve success.

b. Symptom Relief

• Even when a complete cure is not possible, partial excision or debulking can:

  • Reduce pain

  • Relieve disfigurement or swelling

  • Control recurrent bleeding or ulceration

• In these cases, surgery is palliative but impactful on daily function.

c. Risk of Recurrence

• Recurrence is common, reported in 30–60% of cases, especially after incomplete excision or embolization-only treatment.

• Regrowth may be more aggressive than the original lesion, especially if residual nidus is left behind.

• These highlight the importance of the training and experience of the intervening multidisciplinary medical team.

Surgical treatment can have a significant impact on quality of life,  depending on the outcome and expectations.

• An improved appearance, especially in facial AVMs, can help restore self-esteem.

• Relief from chronic bleeding, pain, or swelling can enhance daily functioning.

• Restoration of airway, speech, or vision in AVMs affecting critical areas.

On the other hand, recurrence can be emotionally and physically devastating, requiring repeat interventions.

The multidisciplinary team's effort is to evaluate each case individually and provide the best possible treatment plan. Surgery can play a crucial role in many AVM cases if carefully planned and executed. 

Embolization

Embolization involves the occlusion of pathological vessels with solid (coils) or liquid embolic agents (such as Onyx, NBCA GLUE). Depending on the location of the arteriovenous malformation and its morphology, embolization is performed intravascularly using small tubes called catheters or percutaneously by direct puncture of the arteriovenous malformation.

Arteriovenous malformations
Science has made great leaps and has led to many discoveries of the pathways that affect the growth and development of vascular tumors and vascular anomalies.  One of the important discoveries is that some of these pathways are the same as the ones used by some cancers.  In recent years, specialists have been repurposing the use of medications that target the abnormal pathway to treat patients with vascular anomalies.  Since most of these medications are new and are still actively studied, they are mostly used “off-label”, meaning not officially approved for this use yet.

The two main pathways that have been explored are the PI3K/AKT/mTOR and RAS/RAF/ERK/MEK, both of which lead to cell growth.  Mutations (or genetic changes to the genetic make-up of the abnormal cells) of the RAS/RAF/ERK/MEK pathway tend to be seen in “high blood flow” anomalies, such as arteriovenous malformations (AVM).  Medicines that target BRAF (such as Dabrafenib) and MEK (such as Trametinib) are being used in many patients with AVM.  An additional pathway of therapy prevents the formation of blood vessels- a process known as angiogenesis.  Medications that target VEGF, such as Thalidomide and Bevacizumab (Avastin) have a role in the management of AVM.  It is not unusual for the pathways to “crosstalk,” and it is always helpful to obtain a tissue sample (biopsy) of the affected tissue to identify a mutation.  This information helps reinforce the diagnosis and may offer an additional treatment option.

The main advantage of targeted medicinal treatment is that the entire vascular anomaly is treated at the microscopic level, without affecting normal tissue.  Most medications are taken by mouth, and many patients notice rapid improvement to pain, bleeding, and loss of function.  These medicines also tend to allow for less bleeding during surgery.  As with any therapy, side effects may occur, which include heart, eye and skin toxicities, although they are usually self-limited and not permanent with close monitoring and supportive care.  We will discuss with you in detail the possible side effects. 

The decision on which medication, and the best timing of treatment remains individualized.  There are treatment and patient factors that influence whether someone undergoes surgery only, sclerotherapy/ embolization, medication use or a combination of the above.  Your treatment team will review all relevant factors and make a recommendation on the best path.