AVM Flashcards
What is the avg age at presentation for arteriovenous malformations (AVMs)?
30 yrs (10–40 yrs).
What is the nidus of an AVM?
The nidus is a tangle of abnormal arteries/veins connected by at least 1 fistula.
What is the main histologic abnormality in the vasculature of an AVM?
Absence of smooth muscle layer; ↑ venous pressure (fibromuscular thickening with incomplete elastic lamina)
What is the morbidity and mortality per bleed for AVMs?
Morbidity: 30%–50%/bleed
Mortality: 5%–10%/bleed (1%/yr)
What is the rate of hemorrhage per yr for AVMs?
AVMs have a 2%–4% chance of hemorrhage/yr.
Are most AVM cases familial or sporadic?
Most AVMs are sporadic.
What familial/genetic syndromes are associated with AVMs?
Osler-Weber-Rendu (hereditary hemorrhagic telangiectasia; HHT) and Sturge-Weber syndromes are associated with AVMs.
What characteristics portend an increased risk of hemorrhage from AVMs?
Previous hemorrhage,
increased age,
aneurysm,
deep venous sinus drainage,
deep location,
single draining vein,
and venous stenosis
Aneurysms are found in what % of pts with AVMs?
6%–8% of AVM pts harbor aneurysms.
What are the common presenting signs of AVMs?
Intracerebral hemorrhage (42%–72%)
> seizures (11%–33%)
> HA
> focal neurologic deficit.
Children are more likely to present with hemorrhage than adults.
What imaging modality is ideal to r/o a bleed?
CT is ideal to r/o cerebral bleeds.
What is the gold standard imaging modality for AVMs?
Angiography is the gold standard modality for imaging AVMs.
What other imaging modalities can be used for AVMs? What are their advantages?
CT angiography (good vascular detail),
MR angiography (good anatomy detail),
functional MRI (eloquent areas),
Diffusion tensor imaging (for white matter tracts)
What scale is used to evaluate AVM pts for surgery?
Spetzler-Martin scale/grading system (totals possible: I–V).
What 3 AVM characteristics in the Spetzler-Martin scale are predictive of surgical outcomes?
AVM characteristics that predict surgical outcome:
1. Diameter (<3 cm = 1, 3–6 cm = 2, >6 cm = 3)
- Location (noneloquent area = 0, eloquent area = 1)
- Pattern of venous drainage (superficial = 0, deep = 1)
Smaller score = better surgical outcome
How does AVM diameter/size scoring correlate with surgical outcomes?
The smaller the AVM diameter/size (<3 cm), the better the outcomes.
What brain areas are considered eloquent?
Eloquent areas include:
sensorimotor,
language,
visual,
thalamus, hypothalamus,
internal capsule,
brainstem, cerebellar peduncles,
and deep cerebellar nuclei.
What are the 4 Tx options for AVMs?
Observation, Surgery, radiosurgery, and endovascular embolization
What is the goal of Tx with AVMs? Why?
Complete obliteration is the goal, since there is no benefit or ↑ risk of bleed if the obliteration is partial.
Is Tx of unruptured AVMs beneficial?
Controversial but likely not. Recent studies suggest tx if unruptured led to increased risk of hemorrhage, clinical impairment, and death (Wedderburn CJ et al., Lancet Oncol 2008; van Beijnum J et al., JAMA 2011)
Which lesions are most amenable to surgery?
Those with low (I–III) Spetzler-Martin scores are most amenable to surgery.
What is frequently done for grade III lesions before surgery?
Embolization can be performed for grade III lesions before surgery.
What is the main advantage of surgery?
Immediate cure and reduction in the risk of hemorrhage.
For what AVM lesions is SRS preferred?
Radiosurgery is preferred for lesions <3 cm that are located in deep or eloquent regions of the brain.
