In addition to anatomic corridors of access, a hematoma may provide access to an eloquent AVM and even facilitate dissection by separating the nidus from the brain. Nevertheless, an AVM in an eloquent locale such as the motor cortex, internal capsule, or brainstem, without a corridor of access, regardless of size, may be deemed inoperable. 6 In essence, any small AVM would be deemed operable by this scheme given that all AVMs of less than 3 cm would receive a grade of I to III. The Spetzler–Martin grading scale, used to predict surgical risk, underscores the importance of size as a factor influencing the difficulty of resection. The associated risk is up-front, with outcomes generally improving as follow-up time accumulates. Microsurgical resection of AVMs is the time-honored treatment modality that affords an immediate cure in the vast majority of patients. Unruptured, asymptomatic small AVMs should also be treated given the lifetime risk of hemorrhage and the development of focal deficits or seizures, particularly in younger patients. To potentially mitigate and prevent the progression of seizures or focal neurologic deficits, we also recommend the treatment of symptomatic small AVMs. Given the risk of rehemorrhage, we recommend treatment of all small AVMs that have bled. 2– 4 Although a small AVM size is not consistently noted among these studies, it has also been proposed as a risk factor for hemorrhage, potentially as a result of increased feeding artery pressures. 3 Associated aneurysms, deep venous drainage, and a deep location were often associated with further elevated hemorrhage risks, independent of hemorrhagic presentation. 2– 4 Early re-bleed rates in the first year range from 6% to as high as 15% in some studies.
1– 4 More recent reports have consistently shown an increased risk of hemorrhage among patients with a prior hemorrhage, with overall annual re-bleed rates of 3 to 7%. Reviewing both modern and older natural history studies reveals a consistent overall annual hemorrhage rate of 2 to 4% for AVMs. Approximately 7 to 10% of patients with AVMs present with nonhemorrhagic focal neurologic deficits, in some cases attributable to local steal phenomena. 1 Factors associated with a greater risk of epileptogenesis from AVMs include younger age, a cortical or temporal location (or both), and a larger size. In reviewing the natural history, microsurgical, and radiosurgical results for small AVMs, we show that microsurgery should be considered first, unless the lesion is in a surgically inaccessible, eloquent location or the patient is medically unfit for surgery.Īlthough most patients with AVMs come to attention because of hemorrhage, 20% present with seizures, with an annual development rate of de novo seizures of 1%.
Microsurgical resection is the time-honored therapeutic modality in the treatment of AVMs, providing immediate and often definitive therapy. Small AVMs (less than 3 cm), particularly if symptomatic or certainly if they have previously hemorrhaged, are ubiquitously considered for intervention. Observation is a consideration for large AVMs in eloquent locations (high grade), particularly if they are asymptomatic or discovered in older patients. 1– 4 Management options include observation, microsurgical resection, radiosurgery, embolization (often adjunctive or palliative), or a combination of these approaches ( Table 17.1). Microsurgery for Small Arteriovenous MalformationsĬerebral arteriovenous malformations (AVMs) are a considerable source of morbidity and mortality in neurosurgical patients, often as a consequence of hemorrhage but also as a result of debilitating seizures and neurologic deficits.
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