Brain AV malformations

Abnormal connections between arteries and veins leading to arteriovenous shunting within intervening network of vessels.

Parenchymal webs of dysplastic arteries that shunt into the venois system, with approximate prevalence of 0.1%

AVMs harbor a 2% risk of rupture per year that increases to 4% for hemorrhagic AVMs and 6% within the first year of a hemorrhage.

The network of vessels in a brain AV malformation is ref2242ed to as the nidus.

Refers to a cluster of blood vessels in which the arteries connect directly to veins without intervening capillary bed.

Brain AV malformations refer to abnormal connections between arteries and veins leading to arteriovenous shunting with an intervening network of blood vessels,

Typically located in the supratentorial part of the brain.

Brain arteriovenous malformation lesions may be compact or diffuse.

In 77% of cases the arteriovenous malformation is 2-6 cm in diameter.

Accounts for approximately 11% of cerebrovascular malformations, while venous angiomas account for 64% of cases.

Prevalence varies between 15 and 18 per hundred thousand adults(Al-Shhahi R et al).

Is a incidental finding on brain MRI in approximately .05% of the population.

Detection rate is one per 100,000 adults per year (Stapf C et al).

Found in approximately 0.05% brain MRIs incidentally.

Detection rate 1 per 100,000 adults per year.

Prevalence about 0.5% in postmortem studies.

Headache without distinctive features is the presenting symptom in 48% of cases.

50% present with symptoms other than hemorrhage.

Approximately 50% of patients with brain AVMs present with intracranial hemorrhage.

First year hemorrhage rate 0.55 per 100,000 person-years.

More likely to have symptoms than other types of vascular malformations.

Categorized by blood supply: pial of parenchymal AV malformations supplied by internal carotid or vertebral circulation while dural AV malformations supplied by the external carotid circulation.

Mixed AV malformations are supplied by both circulations.

Pial malformations are congenital and the most common AV malformations.Brain arteriovenous malformation-mixed Av malformations are supplied by both circulations.

Pial malformations are congenital and the most common AV malformations.

Approximately half of patients with brain AVMs present with intracranial bleeding, with a first ever hemorrhage rate of 0.55 per hundred thousand persons per year.

Commonly use grading scale is the Spetzler-Martin Grade (SMG) scale, a composite score of nidus size:

Nidus size< 3 cm, 3-6 cm,> 6 cm; 1 to 3 points

Eloquence of adjacent brain-one point if located in brainstem, thalamus, hypothalamus, cerebellar peduncles, or, sensorimotor, language, or primary visual context.

Presence of deep venous drainage-1 point if any or all drainage is through deep veins, such as internal cerebral veins, basal veins or precentral cerebellar veins (Spetzler RF, Martin NA.

Risk of subsequent AVM hemorrhage increases when patients present with hemorrhage, have the venous drainage, when associated with aneurysms, or one located in the deep location.

Annual hemorrhage risk as low as 0.9% in patients with and unruptured, superficially located, and associated with superficial drainage.

Deeply seated, ruptured, and associated with deep venous drainage lesions may be associated with an annual hemorrhagic risk as high as 34% (Stapf C et al).

Ruptured brain AVMs have a hemorrhagic risk of 4.5%-34% compared to previously unruptured ones of 0.9-to 8% and therefore interventional treatment is suggested.

The goal of treating AVM of the brain is to prevent hemorrhage, with control of seizures and stabilization of neurological deficits as other aims.

Microsurgery has a low risk of complications for SMG stage I and stage II lesions, with cure.

Stereotactic radiosurgery is effective for malformations smaller than 3.5 cm, but complete obliteration of the nidus requires approximately 1-3 years after treatment and cure is not always obtained.

The two-year obliteration rate after stereotactic radiosurgery is probably in the range of 40%, rather than the commonly cited 80%(Heffez DS et al).

SMG grade IV or V generally require multi modality management.

Delayed hemorrhage and radiation edema one necrosis can occur as late complications of stereotactic radiosurgery.

Small malformations can be treated with embolization therapy.

Larger malformations can be treated with embolization to decrease size to make the lesions amenable for radiosurgery, or eliminate hemorrhage.

Embolization utilizes micro-catheters to deliver embolic material to arteries feeding the nidus.

In a systematic review and meta-analysis of 137 observational studies with 13,698 patients and 46,314 patient years of follow-up of brain AVMs after interventional treatment: case fatality was 0.68 per 100 person-years overall, 1.1 after microsurgery, 0.5 after stereotactic radiosurgery, and 0.96 after embolization (van Beijnum et al)

In the above study intracranial hemorrhage rates world 1.4 per 100 persons overall, 0.18 after microsurgery, 1.7, after stereotactic radiosurgery and 1.7, after embolization.

In the above study more recent treatment protocols were associated with lower case fatality rates, but increased rates of hemorrhage,

In the above study small lesions, male sex, and strictly deep venous drainage lesions are associated with lower fatality and lower hemorrhagic rates.

In the above study complications with permanent neurologic deficits or death occurred, it a median of 7.4% of patients after microsurgery, 5.1% after stereotactic radiosurgery, and 6.6% after embolization.

In the above study successful brain AV malformation was achieved in 96% of patients after microsurgery, 38% after stereotactic radiosurgery and 13% after embolization.

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