Preparation for Surgery for Cerebral Arteriovenous Malformations in Children

Indications for Procedure

The operative goal is complete removal of the lesion. Operative indications center on assessing the balance between operative risk versus risk of hemorrhage. Natural history/rupture risk based on adult cohorts may not translate to children (124). The decision to resect an AVM is based on several factors (16,94,95,96):

• Eloquence of region: The following areas of the brain are considered eloquent: sensorimotor, language, and visual cortex; hypothalamus and thalamus; internal capsule; brainstem; cerebellar peduncles; and deep cerebellar nuclei (16).
• Superficial vs deep (including the internal cerebral, basal, and precentral cerebellar veins) venous drainage patterns: AVMs with deep venous drainage may carry a higher risk of operative morbidity and mortality, but also a higher risk of rupture (16,124,126,127).
• Size of AVM: AVM size has a complex relationship with operative risk versus risk of hemorrhage. Smaller (less than 3 cm) AVM size is a risk factor for increased risk of rupture, which may occur when there is higher arterial inflow pressure into a smaller nidal area (124). However, larger AVM size is associated with higher operative morbidity and mortality due to increased technical difficulty of resection, more normal adjacent neural tissue, longer operative time, and more feeding arteries to control (16).
• Associated aneurysms: Analyses of the natural history of brain AVMs have demonstrated that the absence of associated aneurysms is associated with favorable outcomes, and the presence of these lesions is associated with increased risk of AVM rupture (94).
• Number of arterial feeders (16,124): The presence of a single arterial feeder (versus multiple arterial feeders) is associated with increased risk of AVM rupture (126). Lesions with single arterial feeders often have smaller nidal sizes, which are associated with increased risk of rupture (127). While the number of feeding arteries may affect the initial presentation of AVMs (ruptured versus unruptured), this has not been shown to affect obliteration rates, symptomatic complications, or functional outcomes after surgery (128).
• Recent hemorrhage: Compared to unruptured AVMs, ruptured AVMs are at higher risk of (repeat) hemorrhage, particularly during the first year after rupture; risk of re-hemorrhage decreases and converges thereafter (129). Hemorrhage may lead to neurological deficits and, in some cases, may be fatal (97). However, recent hemorrhage may facilitate surgery because hematomas can separate an AVM from healthy brain tissue and/or obliterate some of the AVM’s arterial supply (97).
• Clinical deterioration: Poor functional status at presentation, specifically modified Rankin Scale > 2, has been associated with poor outcomes and increased mortality after AVM surgery (130).
• Risk of other treatment options: Consider the risk of complication from other modalities of therapy (such as radiation injury to the developing brain).
• Spetzler-Martin grading system: Several of these factors are combined in the Spetzler-Martin grade that incorporates eloquence of location, pattern of venous drainage, and size. The Spetzler-Martin grade is considered predictive of outcome from surgical management (16).

Preoperative Orders

• See Presentation of Cerebral Arteriovenous Malformations in Children, Admission Orders.

Anesthetic Considerations

• Anticipate large blood loss: Consult anesthesiologist and take appropriate measures to ensure multiple large-bore IVs are present and adequate blood products are in the room.

Devices to Be Implanted

• Vascular clips: An array of AVM and aneurysm clips should be available.

Ancillary/Specialized Equipment

• Operating microscope
• Multiple suctions
• Retraction system