Arteriovenous Malformations

 

  • Four Types of Intracranial vascular malformations
    • Arteriovenous malformations
    • Capillary telangiectasias
    • Cavernous angiomas
    • Venous angiomas
  • Introduction
    • AVM are rare, complex vascular structures that can occur within the parenchyma (ie pial malformations), dura, or both. Most commonly patients present with seizures or symptoms resulting from seizures..
    • Epidemiology: 0.005-0.6% in the general population
      • Most commonly present between 20-40yo (Mean 31.2yo)
      • ¼ hemorrhage within the first 15 years of life
    • Presentation
      • Hemorrhage- 53%
      • Seizures- 20-25%
      • Headaches
      • Learning disorders- thought to be secondary to direct injury or vascular steal phenomenon
    • Natural history
      • Following a hemorrhage- 7% risk of rupture for that year (returns to baseline after 3 years)
      • Annual lifetime risk of hemorrhage: 2-4% chance/year
      • Mortality rate 1% per year
      • Combined major morbidity and mortality rate 2.7% per year
    • Hemorrhage risk factors
      • Prior hemorrhage, AVM size (controversial but small AVM are thought to have a higher bleeding risk), deep or inadequate venous drainage, intranidal aneurysms, HTN, periventricular location
    • Outcome
      • Mortality: 5-30%
      • Morbidity: 20-30%
  • Imaging findings:
    • CT- can appear normal but is the most sensitive test for evaluating an acute hemorrhage. Normally see serpiginous isointense to slightly hyperintense vessels (strongly enhance)
      • CTA- normally give an excellent view of the MIPs
      • 25-30% calcified
      • Mass effect, edema, hemorrhage
    • MRI- more sensitive for subtle lesions
      • Tightly packed flow voids
      • Gliosis- hyperintense on T2: thought to be secondary to a steal phenomenon in which blood is shunted through the relatively low resistance AVM instead of through normal tissue.
      • Variable signal according to age of hemorrhage
    • Angiogram- allows finer detail as it relates to feeding vessels and draining veins: Gold standard with a low risk of stroke (0.3-0.8%)- actually lower than angiograms for TIA/stroke (3-3.7%)
      • Classic features: enlarged arteries, veins, AV shunting (early draining veins)
      • Yield in patients with a spontaneous ICH of finding an underlying vascular abnormality with angio
      • Age <45: 50%
      • >45: 18%
      • History of HTN: 9%
      • No history of HTN: 44%
    • 9% of patients will have multiple AVMs
  • Spetzler-Martin Grade- used to predict operative risk
    • Size of AVM: <3, 3-6, >6cm
    • Eloquence of adjacent brain- hypothalamus, thalamus, brain stem, cerebellar peduncles, sensorimotor cortex, language and visual areas.
    • Pattern of venous drainage: superficial or deep
  • Classic Treatment Evaluation
    • Spetzler-Martin Grade I-III: 94-100% success rate with complete operative resection
      • Approximately 80% of all AVMs
      • Morbidity: 0-5%
      • Mortality- 0-3.9%
    • SM Grade IV-V: Frequently require adjuvant treatment and are felt to have an increased risk of hemorrhage (10%/year-controversial number)
      • Morbidity: 22%
      • Mortality: 11-38.4%
  • Surgery
    • Timing- Early surgery should be considered when there is a significant clot burden producing neurological deficit or if the lesion is easily accessible
    • Intraoperative angiography- can be used to resect residual
    • Complications
      • New onset seizures: 6-22%- often will prophylax
      • Cerebral edema- 3%: can alter vascular dynamic resulting in passive brain engorgement and occlusive hyperemia
      • Rehemorrhage- normally seen with residual, high grade AVM
      • Vasospasm- <1%
      • Intracranial thrombosis
  • Radiosurgery
    • Gamma knife- 201 gamma ray beams deliver dose at isocenter
      • Normally deliver 12-25Gy (UAB 17.5 Gy)
    • Mechanism: produces endothelial cell damage that induces smooth muscle proliferation that leads to stenosis and occlusion (endarteritis obliterans)
    • Effectiveness
      • <3cm- 75-95%
      • >3cm- <70%
    • Hemorrhage risk- controversial: initially felt to be increased risk
      • 1.8-4.8% risk in first 2 years
      • Increased risk with unsecured associated (not necessarily intranidal) aneurysm
    • Seizure freedom: 51-80%
    • Complications:
      • Neurologic deficit: 8%
      • Radiation injury, Radiation necrosis
      • CN injury
      • Worsened seizures
      • Death
  • UAB Gamma Knife: 205 patients treated with 17.5Gy
    • SM Grade 1 and 2 = 95.5% resolution rate
    • SM Grade 3 = 66.7%
    • SM Grade 4 and 5 = 70.6%
  • Associated aneurysm
    • Seen in 15-25% of patients
    • Three types:
      • Feeding artery aneurysms- most common type secondary to high flow: 17%
      • Intranidal aneurysm- 8%
      • Incidental aneurysms: 0.8% (same as general population)
    • 7% risk of hemorrhage per year
    • Generally treat aneurysm first (if feeding artery)
  • Genetic Conditions
    • Familial intracranial AVMs- rare with younger age of onset
    • Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu)
      • Spontaneous recurrent nosebleeds
      • Mucocutaneous telangiectasia
      • Visceral involvement
      • An affected first degree relative
      • CNS findings: AVM, cav mals, aneurysm
    • Sturge-Weber- aka encephalotrigeminal angiomatosis: port wine stains, leptomeningeal venous angiomas
    • Wyburn Mason syndrome- AVM in the brain and retina
  • AVM and Pregnancy
    • Common cause of IPH in pregnant women: 21-48% of hemorrhages
    • Mean gestation age is 30 weeks: can be seen earlier or even immediately following delivery
    • Mortality- worse than general population
      • Up to 28%
      • Fetal mortality- 14%
    • Re-hemorrhage- 25-30% rebleed during the same pregnancy
    • Treatment- prompt surgical treatment is recommended
    • Delivery: No clear guidelines on vaginal versus cesarean delivery
    • Anticipating pregnancy: Recommend that AVM be treated first secondary to the increased mortality associated with a hemorrhage.
      • Same risk (3.5%) but worse outcome
  • ARUBA Trial
    • A randomized trial between treatment and observation
    • 35 intervention patients had a stroke/death versus 11 in the observation group
    • The participating center was able to choose which intervention to employ including endovascular approach alone
    • The study was stopped
    • Poorly designed study in that it did not compare AN intervention with observation. It compared whatever you wanted to do that may or may not be an acceptable treatment option in what may or may not be a competent technician’s hands with medical management.
  • Recommended reading for AVM Podcast
Joseph MillerArteriovenous Malformations

Leave a Reply

Your email address will not be published. Required fields are marked *