Background: Hemorrhage from cerebral arteriovenous malformations (AVMs) represents 2% of all strokes. AVMS are a cause of hemorrhage in young adults. The mortality associated with a cerebral arteriovenous malformation is 10% and the morbidity is substantial at 50%.
Pathophysiology: AVMs are congenital lesions composed of a complex tangle of arteries and veins connected by fistulas. The arteries have a
deficient muscularis layer. The draining veins are often dilated due to the high velocity of blood flow through the fistulae, and there is no
intervening capillary bed. It is unknown how the abnormal vessels appear or exactly when the process begins. Deranged production of
vasoactive proteins is under investigation as the angiogenetic link to pathophysiology.
AVMs produce neurologic dysfunction through 3 main mechanisms. First, hemorrhage may occur in the subarachnoid space, the intraventricular
space, or most commonly, in the brain parenchyma. Second, in the absence of hemorrhage, seizures may occur as a consequence of AVM:
approximately 50% of patients present with seizure disorder. Finally, but rarely, a progressive neurologic deficit, over a few months to several
years, may also occur. These slowly progressive neurological deficits are thought to relate to siphoning of blood flow away from adjacent brain
tissue (the \"steal phenomenon\"). Neurologic deficits may be alternatively explained by the mass effect of an enlarging AVM or venous
hypertension in the draining veins.
Frequency:
In the US: The prevalence of cerebral AVM in the United States is not known. The lifetime detection rate in the general population is
approximately 1:100,000.
Internationally: The worldwide prevalence is not known. It is usually assumed to be similar to the U.S. worldwide.
Mortality/Morbidity: Although 300,000 persons in the US may harbor AVMs, it is estimated that only 12% of AVMs become symptomatic.
Mortality from hemorrhage occurs in 10-15% of cases, and morbidity occurs in approximately 50%.
Hemorrhage: the overall risk of intracranial hemorrhage in patients with known AVM is 2-4% per year. Specific angiographic features of
the AVM increase the risk of first or subsequent hemorrhage. These include a small-sized venous drainage that is directed deep into the
brain, not superficially, and relatively high arterial and venous pressures within the AVM nidus. This last feature can be measured only
angiographically, with superselective catheterization. Recurrent hemorrhage occurs in 15-20%, usually within the first year of the bleeding
incident. Although the initial presentation of a cerebral hemorrhage may be indistinguishable from other causes of hemorrhage, recovery
tends to be better, partly because of the relatively younger age of AVM patients and partly due to functional cerebral reorganization in
patients with cerebral AVMs.
Seizures: They occur as the presenting symptom in one-quarter to one-half of AVM patients. These may be focal or become secondarily
generalized. Satisfactory treatment of seizures is usually possible with standard anticonvulsants.
Migraine: Headache occurs in 10-50% of patients with AVM. Refractory headaches may be a presenting symptom if seizures or
hemorrhages do not occur. The headache may be typical for migraine or may be present with a less specific complaint of more
generalized head pain.
Race: No racial predilection has been identified.
Sex: Both sexes are affected equally.
Age:
Despite the presumed congenital origin of AVMs, the clinical presentation most commonly occurs in young adults.
AVM hemorrhage or seizure as an incident event may occur in young children or adults over 40; however, childhood migraine is common.
A history of subtle learning disorder is elicited in 66% of adults with AVMs. This suggests early effects that are largely subclinical and do
not come to medical attention.
Treatments include :
anticonvulsants
Surgery
Intravascular embolization
radiosurgery
combinations of above
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