Management of CNS Arteriovenous Malformations
The management of CNS arteriovenous malformations should be based on a multimodality treatment approach tailored to the Spetzler-Martin grade, with surgical extirpation strongly considered as the primary therapy for grade I and II lesions, combined embolization and surgery for grade III lesions, and conservative management often preferred for grade IV and V lesions due to high surgical risk. 1
Natural History and Risk Assessment
Hemorrhage Risk
- Annual risk of initial hemorrhage: 2-3% per year 1
- Mortality from first hemorrhage: 10-30% 1
- Long-term disability among survivors: 10-20% 1
- Recurrent hemorrhage risk is elevated in the first year after initial bleed:
Risk Factors for Hemorrhage
Several angiographic features increase hemorrhage risk:
- Previous hemorrhage 1, 2
- Deep or infratentorial location 1, 2
- Deep venous drainage 1
- Small AVM size (paradoxically) 1
- Presence of intranidal aneurysms 1, 3
- Single draining vein 1
Diagnostic Evaluation
A comprehensive evaluation requires:
- MRI with MR angiography to define topography and localization 1
- Four-vessel cerebral angiography (gold standard) to define:
- Arterial supply
- Nidus characteristics
- Venous drainage patterns
- Associated aneurysms (present in 7-17% of cases) 1
Treatment Decision Algorithm
Grade I and II AVMs
- Primary recommendation: Surgical extirpation 1
- Excellent outcomes: 92-100% favorable for grade I, 95% for grade II 1
- For small lesions in high-risk locations: Consider stereotactic radiosurgery 1
Grade III AVMs
- Primary recommendation: Combined approach with embolization followed by surgery 1
- Outcomes: 68.2% excellent/good short-term, improving to 88.6% in longer follow-up 1
Grade IV and V AVMs
- Primary recommendation: Conservative management due to high surgical risk 1
- Surgical outcomes: 73% excellent for grade IV; 57.1% good/excellent for grade V with 14.3% poor outcome and 4.8% mortality 1
- Consider palliative embolization for progressive neurological deficits due to high flow or venous hypertension 1
Surgical Management
Timing of Surgery
- Generally elective except for life-threatening hematomas 1
- For complex AVMs with hematoma: Remove blood clot only, defer AVM resection until full angiographic evaluation 1
Surgical Technique
- Microsurgical approach with sequential steps:
- Control and divide arterial feeders first
- Excise the nidus
- Resect draining veins last 1
- Goal: Complete obliteration confirmed by intraoperative or postoperative angiography 1
Associated Aneurysms
- Present in 7-17% of AVM patients 1
- Management approach:
Endovascular Treatment
Indications for embolization:
- Presurgical embolization of large cortical AVMs 1
- Size reduction before radiosurgery 1
- Palliative embolization for symptomatic, inoperable AVMs 1
- Treatment of associated aneurysms or pseudoaneurysms 1
Perioperative Considerations
Anesthetic Management
- Maintain normotension or controlled hypotension
- Avoid cerebral vasodilators
- Maintain euvolemia, normothermia, and mild hypocapnia 1
Postoperative Care
- Neurological intensive care monitoring for at least 24 hours 1
- Arterial blood pressure monitoring
- Maintain normotensive, euvolemic state 1
- Consider tight blood pressure control in selected cases 1
- Confirm complete resection with postoperative angiography 1
Special Considerations
Brain Edema/Hemorrhage Prevention
Two competing theories exist regarding postoperative complications:
- Normal perfusion pressure breakthrough (NPPB): Staged reduction of blood supply may help 1
- Occlusive hyperemia: Caused by arterial stagnation or venous outflow obstruction 1
Hereditary Associations
- Some CNS AVMs occur in association with hereditary hemorrhagic telangiectasia (HHT) 4
- These cases may present with multiple AVMs and require family screening