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.
What is the main disadvantage of SRS for AVMs?
The main disadvantage of SRS is the lag time of 1–3 yrs to complete obliteration (i.e., continued bleeding risk).
How does RT lead to AVM obliteration?
Vascular wall thickening (fibrointimal hyperplasia) and luminal thrombosis from RT effect result in obliteration of the AVM.
Is the bleeding risk completely eliminated after SRS?
No. It is reduced by ∼54% during latency period and 88% after obliteration but not eliminated. (Maruyama K et al., NEJM 2005; Yen CP et al., Stroke 2011)
On what do SRS cure rates for AVMs primarily depend?
Size of AVM: 81%–91% if <3 cm, lower if >3 cm (Maruyama K et al., NEJM 2005)
Radiation dose
What can be done for high-grade AVMs (IV–V) not amenable for surgery?
Staged SRS (different components targeted at separate sessions) (Sirin S et al., Neurosurg 2006)
For which AVMs can embolization be curative?
AVMs <1 cm that are fed by a single artery can be cured by embolization alone.
How are AVMs with feeding artery aneurysms managed?
If the aneurysm is >7 mm in diameter, clip or coil the aneurysm 1st, then treat the AVM. The aneurysm is at greater risk for rupture if the AVM is treated 1st.
What SRS doses are commonly used for AVMs?
Lesions <3 cm: 21–22 Gy to 50% IDL. If the lesion is in the brainstem, lower the dose to ≤16 Gy.
Lesions >3 cm: 16–18 Gy to 50% IDL
What are the reported rates of permanent weakness or paralysis, aphasia, and hemianopsia for grades I–III AVM pts treated with surgery?
The rate of serious postsurgical complications is 0%–15%.
What are common early and delayed complications after SRS for AVMs?
Early: seizures (up to 10%), n/v, HA
Late: seizures, neurological deficit, hemorrhage, radionecrosis (1%–3% risk), edema, venous congestion, cyst formation
What is the incidence of transient vs. permanent neurologic complications after SRS for AVMs?
Complications after SRS for AVMs are as follows: transient (5%) vs. permanent (1.4%).
On what 2 factors do complication rates after SRS for AVMs primarily depend?
Size of AVM and RT dose.
What does the follow-up entail after Tx for AVMs?
Adequate follow-up includes routine H&P + MRI q6mos for 1–3 yrs, then annually.
What study needs to be performed once the MRI shows evidence of AVM obliteration?
An angiogram needs to be performed (in addition to MRI) to confirm complete AVM obliteration.
Compare and contrast advantages and disadvantages of different management options for AVM
