Management of Arteriovenous Malformations Without Portal Hypertension
For intracranial AVMs without portal hypertension, surgical extirpation should be strongly considered as the primary treatment for Spetzler-Martin grade I and II lesions, while grade III lesions benefit from combined embolization followed by surgery, and grade IV-V lesions generally should not undergo surgical treatment alone due to high risk. 1
Risk Stratification and Initial Assessment
The baseline annual hemorrhage risk for unruptured intracranial AVMs is 2-3% per year, which increases dramatically to 6-18% in the first year following an initial hemorrhage. 2 High-risk features that increase hemorrhage probability include:
- Small nidus size 2
- Deep venous drainage or single draining vein 2
- Intranidal aneurysms 2
- Periventricular or intraventricular location 2
Baseline brain MRI/CT should be obtained if not recently performed, with routine surveillance MRI every 6-12 months to assess AVM stability. 2
Treatment Algorithm Based on Spetzler-Martin Grading
Grade I-II AVMs (Low-Grade Lesions)
Surgical extirpation is strongly recommended as the primary treatment modality, achieving 92-100% favorable outcomes. 1, 2 For small lesions where surgery poses increased risk based on location or feeding vessel anatomy, radiosurgery should be strongly considered as an alternative. 1
Grade III AVMs (Intermediate-Grade Lesions)
A combined modality approach with embolization followed by surgery is often the optimal strategy, achieving 68-89% good outcomes. 1, 2 This staged approach reduces operative blood loss, shortens surgical times, and allows occlusion of deep, surgically inaccessible feeding vessels such as anterior/posterior perforating vessels, choroidal vessels, or posterior cerebral vessels. 1
Grade IV-V AVMs (High-Grade Lesions)
Surgical treatment alone is not recommended due to high risk; a multidisciplinary approach with consideration of observation versus staged treatment is appropriate. 1, 2
Presurgical Embolization Strategy
When embolization is indicated, the goals are to:
- Decrease nidus size of the AVM 1
- Occlude deep, surgically inaccessible arterial feeding vessels 1
- Occlude intranidal aneurysms and high-flow fistulas 1
Critical pitfall to avoid: Proximal occlusion of arterial feeding vessels without occluding the AVM nidus has a deleterious effect on surgery due to inevitable development of cortical transmedullary and transdural collaterals. 1 Trans-arterial coil embolization or ligation of feeding arteries where the nidus is left intact are incorrect approaches that may result in proliferation of the lesion. 3
Surgical resection should occur within several days after the final feeding artery embolization to prevent development of new collateral flow. 1
Perioperative Blood Pressure Management
Normotensive and euvolemic conditions should be maintained postoperatively, with tight blood pressure control using agents that do not act in the central nervous system. 1 Emergence hypertension is frequently encountered after AVM resection and requires careful management. 1
For marginally perfused areas that may be critically dependent on collateral perfusion pressure, maintenance of low or even normal blood pressure may be inadequate and result in infarction if hypoperfusion is unrecognized. 1
Management of Associated Aneurysms
Intracranial aneurysms are found in 7-17% of patients with AVMs. 1 These should be approached during the same surgery if the operative field is adequate, or treated separately with endovascular or open surgical obliteration. 1 Aneurysms on feeding arteries may involute after AVM resection, while saccular aneurysms at typical circle of Willis locations require definitive treatment. 1
Postoperative Monitoring Protocol
Neurological intensive care monitoring for at least 24 hours is required, with blood pressure monitored via arterial catheter and urine output via indwelling catheter. 1 An angiogram should be performed during the immediate postoperative period to confirm complete resection. 1
New neurological deficits warrant immediate CT scan to rule out hemorrhage or hydrocephalus, with MRI and diffusion-weighted imaging if infarction is suspected. 1
Extracranial AVMs (Peripheral Vascular Malformations)
For peripheral AVMs, endovascular ethanol sclerotherapy produces the best long-term outcomes with minimum recurrence for surgically inaccessible, infiltrating, extra-truncular AVMs. 3 For surgically accessible lesions, surgical resection may be the treatment of choice, with preoperative sclerotherapy or embolization supplementing subsequent surgical excision. 3