Indications
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Eloquently located ruptured arteriovenous malformation (AVM) with significant hematoma and neurologic deficit
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Angioarchitectural features that deem the cortical AVM at higher risk of hemorrhage (e.g., deep venous drainage, intranidal aneurysms, venous stenosis, venous hypertension, previous hemorrhage)
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Worsening neurologic deficits or seizures despite optimal nonsurgical therapy
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Safely treatable cortical AVM in a young patient with lifelong exposure to natural history risks of an AVM
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Psychological burden or personal limitations of activities of living with knowledge of the lesion and its natural history risks of an AVM
Contraindications
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Premorbid conditions increasing surgical risks beyond natural history risks, including coagulopathies or cardiopulmonary compromise
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Asymptomatic AVM within functionally eloquent cortex as defined by location and functional magnetic resonance imaging (MRI)
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Angioarchitectural features that present a high surgical risk, such as a diffuse nidus near or within eloquent cortex in unruptured AVM
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Personal, religious and nonreligious, wishes of patient or family
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Older age or limited life expectancy in asymptomatic patient with fewer years of natural history risk
Planning and positioning
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Preoperative planning includes a detailed study of the location and angioarchitectural features of the AVM, including any angiomatous change, location of the feeding arteries, draining veins, and extent of the nidus. Preoperative imaging should include MRI and catheter-based angiography. Computed tomography (CT) angiography and magnetic resonance angiography may also be performed. Functional and diffusion tensor MRI may be used to assess the functional status and pathway of white matter tracts of the surrounding brain parenchyma.
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Intraoperative mapping may be used in cases in which the AVM is located in or near functionally eloquent cortex.
Figure 28-1:
The patient is placed in a Mayfield head clamp. Shoulder rolls may be used for patients with limited neck mobility. For frontal, temporal, and sylvian AVMs, the head is turned so that the craniotomy flap is at the highest point of the head. For lesions in the posterior parietal, occipital, and posterior fossa, patients can be positioned in the lateral prone position or, rarely, in the sitting position.
Figure 28-2:
After positioning, AVM architecture is mapped out using neuronavigation so that the skin incision is adequate for the bone flap to encompass the brain parenchyma beyond the AVM nidus and all of the cortical arterial feeders and draining veins.
Procedure
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