History
Arteriovenous malformations (AVMs) tend to be clinically silent until the presenting event occurs. Therefore, the diagnosis usually is made at the time of the first seizure or hemorrhage.
A history of minor learning disability is present in as many as two thirds of patients; such dysfunction is rarely apparent in adult life.
A history of headaches is present in as many as half of patients with cerebral AVM. The headaches subsequently may take the form of classic migraine or more generalized headache.
If seizures have occurred, a careful seizure history should be obtained. Seizures are simple, partial, or secondarily generalized.
The effectiveness of anticonvulsant therapy should be observed carefully and monitored before and during treatment.
Physical
Focal neurologic findings are rare in the absence of seizure or hemorrhage in patients with cerebral arteriovenous malformations (AVMs). They are more common in brainstem and deeply located AVMs. They are associated with patient’s age and are more common among women.
Detailed neuropsychological testing may disclose subtle right or left hemisphere dysfunction.
If parenchymal hemorrhage is present, the physical findings are indistinguishable from those due to intracranial hemorrhage of other causes.
Intraventricular hemorrhage generally produces a less severe neurological deficit than hemorrhage into other areas of the brain.
In the rare patients in whom focal neurological deficits are present, the deficit may reflect the location of the AVM.
Causes
No genetic, demographic, or environmental risk factors for cerebral arteriovenous malformations (AVMs) have been identified clearly.
Families with cerebral AVMs are rare, and such pedigrees have been too small to enable linkage studies. From the few family cases reported, the inheritance appears to be autosomal dominant.
In a small minority of cases, cerebral AVMs are associated with other inherited disorders, such as the Osler-Weber-Rendu syndrome (ie, hereditary hemorrhagic telangiectasia), Sturge-Weber disease, neurofibromatosis, and von Hippel-Lindau syndrome.
Complications
The most dreaded complication of arteriovenous malformations (AVMs) is intracerebral hemorrhage (see Prognosis). Treatment decisions are based on the natural history-risk of first or subsequent hemorrhage versus the risk-benefit ratio of treatment.
Surgical complications
Surgical complications may include persistent neurological deficits associated with hemorrhage and stroke.
Surgical outcome risk correlates with score on the Spetzler-Martin scale; higher scores, seen with large-sized AVMs, deep venous drainage, and location of the AVM in eloquent brain regions, increase the surgical risk.
A recent meta-analysis reports a morbidity of 8.6% and mortality of 3.3% after mostly surgical treatment in a series of 2452 patients. [9] The surgical risk for morbidity and mortality for Spetzler-Martin grade of less or equal to 3 has been reported to be 2-6.3% and 0-2%, respectively. The surgical risk for morbidity and mortality for Spetzler-Martin grade IV and V has been reported to be 9-39% and 0-9%, respectively.
Complications of endovascular embolization
Complications of endovascular embolization include persistent neurological deficits related to inadvertent embolization of arteries supplying normal brain tissue or obliteration of the venous outflow leading to intracerebral hemorrhages. The procedure carries an associated risk for morbidity and mortality in the range of 9-22% and 0-9%, respectively.
No long-term outcome studies are yet available; however, as endovascular techniques continue to improve, complication rates are likely to diminish.
Complications of radiosurgery
Complications depend on the size and location of the AVM. AVMs located in eloquent areas and in central locations are more prone to radiation-induced complications.
White matter edema and radiation-induced necrosis may occur during the 1- to 3-year treatment period. Persistent neurological deficits after radiation have been reported in 8% of treated patients.Patients with hemorrhagic presentation have a higher mean annual risk for hemorrhage until radiation-induced obliteration of the AVM is achieved compared to patients with a nonhemorrhagic presentation (6.3% vs 3.9%). The risk for hemorrhage seems to be lower after radiation therapy in patients with hemorrhagic presentation compared to the period before gamma knife radiotherapy was initiated.
Seizure frequency may increase in the first days to weeks after radiosurgery.
The potential for late effects from radiation, such as accelerated atherosclerosis in surrounding blood vessels, does exist.
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Axial T2 MRI showing an arteriovenous malformation with hemorrhage, in the territory of the left posterior cerebral artery.
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T1 axial MRI showing a small subcortical arteriovenous malformation in the right frontal lobe.
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T2 coronal MRI showing an arteriovenous malformation in the left medial temporal lobe.
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Magnetic resonance angiography showing a left medial temporal arteriovenous malformation.
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Angiogram (anteroposterior view) showing an arteriovenous malformation in the deep left middle cerebral artery territory measuring approximately 3 cm in diameter, with a deep draining vein (arrow).
