AV Malformations, Cerebral

• Stephen L. Grupke, M.D., M.S.
• Justin F. Fraser, M.D.

 Basic Information

Definition

Cerebral arteriovenous malformations (AVMs) are congenital vascular lesions that are characterized by blood flow from high-pressure arterial vessels directly into thin-walled veins without passing through an intervening capillary/venule system (Fig. 1).

Synonyms

1. Arteriovenous malformations of the brain

2. AVM

3. Brain AVM

ICD-10CM CODES
Q28.2	Arteriovenous malformations of cerebral vessels

Epidemiology & Demographics

Incidence

1. •

   Detection rates in large prospective studies range from 1.1 to 1.4 per 100,000 person-years.

2. •

   Incidence of hemorrhage, the most common and often most clinically dangerous presentation, is estimated to be 2% to 4% per year.

Prevalence

Estimated about 1.3 per 100,000.

Predominant Sex and Age

1. •

   There is a slight male preponderance; studies of varying populations show 1.04:1 to 1.2:1 M:F ratio.

2. •

   Peak age at time of hemorrhage occurrence is about 20 years, but it can occur in younger and older patients.

Genetics

1. •

   Cerebral AVMs are sporadic in most cases.

2. •

   AVMs are present in about 20% of cases of Osler-Weber-Rendu syndrome (also known as hereditary hemorrhagic telangiectasia [HHT]), an autosomal dominant disorder that results in abnormal blood vessel formation in the skin, lungs, liver, brain, and other organs.

Risk Factors

1. •

   Male sex and presence of HHT are risk factors for AVM.

2. •

   The risk of hemorrhage is increased with prior hemorrhage, presence of a single draining vein, and diffuse nidus morphology.

Physical Findings & Clinical Presentation

1. •

   The most common presentation is hemorrhage; symptoms vary based on location and magnitude of hemorrhage.

2. •

   Patients may present with seizures or neurologic deficits related to mass effect of the AVM nidus.

3. •

   Headache and pulsatile tinnitus may be present.

4. •

   In infants, AVM may present as cyanotic heart failure, macrocephaly, or hydrocephalus.

5. •

   A bruit may be auscultated through the scalp or orbit.

6. •

   AVMs may also present with associated intracranial aneurysms that occur on distant, unrelated vessels, on a proximal artery that feeds the aneurysm (flow-related aneurysm), or within the AVM nidus itself (intranidal aneurysm). Patients may present with a subarachnoid hemorrhage related to the aneurysm rather than to the AVM.

Etiology

In most cases, AVMs are congenital abnormalities caused by failure of formation of a capillary bed between embryonic arterial and venous vascular plexuses during the first trimester of gestation; however, de novo sporadic AVMs have been reported.

Diagnosis

Differential Diagnosis

The differential diagnosis of cerebral AVMs includes other vascular lesions such as cavernous malformations, dural arteriovenous fistulas, and intracranial aneurysms. Table E1 compares vascular malformations, and Table E2 describes major differences between hemangiomas and vascular malformations.

Laboratory Tests

1. •

   CBC and BMP with renal function panel prior to contrast dye administration with CT angiography/cerebral angiogram.

2. •

   PT/INR/PTT should be drawn and corrected in the case of bleeding diathesis.

Imaging Studies

1. •

   In the acute setting, a CT scan of the head to check for hemorrhage and a CT angiogram of the head for characterization of the lesion may be helpful (although calcification may be present and potentially pose as small acute blood).

2. •

   MRI of the brain delineates the nidus and its relationship to surrounding soft tissue structures better than a CT scan; however, in the setting of an acute hemorrhage these details will be obscured.

3. •

   Four-vessel cerebral angiogram (arteriogram) is the best study to evaluate AVM. Angiography in multiple projections helps identify the number and location of feeding and draining vessels for treatment planning (Fig. 2). High-resolution images of the nidus may also reveal other irregularities such as aneurysms that often arise given the abnormal histology of the vessel walls and the high-pressure blood flow traversing them.

   

Treatment

Pharmacologic management of seizures with antiepilepsy drugs and of headaches with oral analgesics can provide symptomatic relief.

Nonpharmacologic Therapy

1. •

   Nonemergent outpatient setting: cerebral angiogram provides characterization of the lesion. Based on angiographic characteristics, the Spetzler-Martin AVM grading system may be used to help guide treatment. In general, grade 5 AVMs are considered unresectable; they are not treated because the risks of treatment likely outweigh the risk of hemorrhage. Current tools for the treatment of AVMs include surgical resection, radiosurgery, and endovascular embolization (with liquid glues or embolic agents).

2. •

   Surgical resection: in low-grade lesions by an experienced neurosurgeon yields a high cure rate (∼95% in published studies). Resection should include removal of all of the nidus of the AVM; failure to remove the complete nidus may increase the risk of recurrence. An increasing Spetzler-Martin grading scale increases risk of neurologic complications. Intraoperative imaging techniques such as indocyanine-green in-field angiography and conventional digital subtraction angiography are used to verify complete resection.

3. •

   Radiosurgery: alternative definitive treatment for AVMs. Traditionally employed to treat AVMs in eloquent areas (e.g., brainstem); stereotactic radiosurgery is increasingly used for higher Spetzler-Martin grade AVM. Reported rates of confirmed radiographic obliteration after AVM radiosurgery range from 47% to 90%.

4. •

   Endovascular embolization involves transarterial superselective blockage of the AVM. It has become an important adjunctive tool. Currently recommended and approved for use before resection, preoperative embolization can reduce arterial flow and pressure within the AVM, assisting in speed and safety of surgical resection. In addition, embolization may often be used to treat intranidal or flow-related aneurysms in coordination with either resection or radiosurgery. Embolization alone in obliterating an AVM is not routinely recommended.

5. •

   Treatment decisions should take into consideration the morbidity associated with the treatment modality versus the risk of future hemorrhage or neurologic deterioration. Disability stemming from intractable seizures or severe headaches may make invasive definitive treatment a more attractive option.

6. •

   Acute cerebral hemorrhage: in the case of an acute hemorrhage, airway and breathing must be maintained, with intubation if necessary. Acute neurosurgical intervention for clot evacuation may be warranted. Microsurgical resection of the AVM may or may not be feasible in the acute setting and is controversial.

Disposition

Whether the patient is receiving elective treatment of a known lesion or presenting with an acute hemorrhage, the patient should receive care in a progressive or intensive care unit with experience dealing with cerebrovascular disease. Once the patient is stabilized, appropriate rehabilitation should be arranged.

Referral

1. •

   Cerebral AVMs should be managed by a qualified neurosurgeon.

2. •

   Referral to radiation medicine for adjuvant radiosurgery should be made when indicated.

3. •

   Referral to an interventional radiologist for endovascular treatment may be warranted.

4. •

   Treatment in a primary stroke center or other specialized center that offers all treatment modalities is recommended.

Pearls & Considerations

Comments

1. •

   No two AVMs are exactly the same; individualization of treatment decisions is the mainstay. Additionally, many AVMs could be effectively treated through one of several modalities or a combination thereof. Factors such as patient age, overall health status, radiographic characteristics, route of surgical access, and potential morbidities of each treatment modality are vital variables in consideration for treatment. The advisability of intervention for unruptured AVMs remains controversial. In a recent randomized trial comparing medical management with specific interventions to obliterate AVMs (neurosurgery, embolization, radiotherapy, or a combination) the rates of neurological disability were higher in the intervention group than with conservative treatment.¹

2. •

   The annual risk of hemorrhage from a cerebral AVM is approximately 3%, but depending on the clinical and anatomical features of the malformations, the risk may be as low as 1% or as high as 33%. The risk of bleeding is increased if the patient has had previous episodes of bleeding, if there is a berry aneurysm on an artery feeding the AVM, and if there is a restriction of venous drainage from the AVM.²

Patient/Family Education

If a patient with a known AVM suffers from acute-onset neurologic deficits or stroke-like symptoms, emergency medical attention is warranted for potential hemorrhage. Presence of AVMs, cerebral or otherwise, in family members should be disclosed to the patient’s primary care physician because the presence of a genetic condition predisposing to cerebral AVMs should be considered.

Suggested Readings

• R. Al-Shahi Salman, et al.: Outcome after conservative management or intervention for unruptured brain arteriovenous malformations. JAMA. 311:1661–1669 2014 24756516

• R.A. Solomon: Connolly ES: Arteriovenous malformations of the brain. N Engl J Med. 376:1859–1866 2017 28489992