Makindo Medical Notes

Related Subjects: |Subarachnoid Haemorrhage |Haemorrhagic stroke

🧠 Arteriovenous malformations (AVMs) are abnormal tangles of blood vessels connecting arteries and veins, disrupting normal blood flow and oxygen circulation. Though rare, they carry a significant risk of intracerebral or subarachnoid haemorrhage, particularly in younger individuals.

📖 About

• Prevalence: Incidence ~20–50 per 100,000; often discovered incidentally on imaging.
• Definition: Direct artery–vein connection without a capillary bed → high arterial pressure damages thin-walled veins → rupture risk.

🔬 Pathophysiology

• Bypass of normal capillary network → poor oxygen exchange.
• ↑ Venous pressure → wall weakness and rupture.
• Most common in cerebral structures; also found in spine, dura, and elsewhere.

🧬 Genetics & Inheritance

• Hereditary Hemorrhagic Telangiectasia (HHT): 10–25% of patients develop brain AVMs.
• Usually sporadic; familial cases rare.
• Affects men and women equally.

🧾 Inherited Conditions Associated with AVMs

• 🎭 Sturge–Weber Syndrome: - Features: Facial port-wine stain, seizures, hemiparesis. - Leptomeningeal angiomatosis may mimic or accompany AVMs.
  
• 👃 Hereditary Haemorrhagic Telangiectasia (HHT): - Genetic disorder of blood vessels → recurrent nosebleeds, telangiectasias, visceral AVMs. - Brain AVMs are a recognised complication.
  

🩺 Clinical Presentation

• Incidental: Often asymptomatic, found on imaging.
• Headache: May be chronic or severe with bleeding.
• Seizures: Common in young adults with cortical AVMs.
• Neurological deficits: Visual changes, weakness, numbness, speech impairment.
• Tinnitus: Audible bruit in large AVMs.

⚠️ Complications

• Intracerebral or subarachnoid haemorrhage.
• Progressive neurological deficits from bleed or mass effect.
• Seizure disorders.
• Hydrocephalus if CSF pathways are obstructed.

📊 Spetzler–Martin Grading (surgical risk)

• Nidus size: Small (<3 cm) = 1; Medium (3–6 cm) = 2; Large (>6 cm) = 3.
• Brain eloquence: Non-eloquent = 0; Eloquent = 1.
• Venous drainage: Superficial = 0; Deep = 1.
• 🔺 Higher total = higher surgical risk.

🔍 Investigations

• 🖼️ CT: First-line in suspected ICH; may show high-density lesion or calcification.
• 🧲 MRI: Best for structural detail; T2 “flow voids” suggest vascular lesion.
• 🩸 Cerebral angiography: Gold standard for diagnosis and planning.
• ⚡ EEG: In seizure presentations.

⚖️ Management

• Conservative: For asymptomatic/low-grade AVMs → monitor with imaging.
• Surgical resection: For accessible AVMs (Grades I–II), especially small, cortical lesions.
• Radiosurgery: SRS or focal beam → causes progressive vessel fibrosis (obliteration in 1–3 yrs).
• Endovascular embolisation: Blocks feeders; often combined with surgery or radiosurgery.

📑 AHA Recommendations

• Unruptured AVMs: Annual bleed risk ~1%. Conservative approach often safer than intervention.
• Ruptured AVMs: Higher rebleed risk (~5%/yr). CTA/MRA/DSA essential; management depends on lesion and patient risk.

📉 Prognosis

• Smaller, surgically accessible AVMs → better outcome after resection.
• Deep venous drainage or associated aneurysm → worse prognosis, higher bleed risk.

📖 References

• NEJM: Arteriovenous Malformations of the Brain
• AHA Stroke Management of Brain AVMs

💡 Exam Pearl: AVMs are direct artery–vein connections → high-pressure venous rupture. Think “young patient, seizures or bleed, MRI flow voids”.