arteriovenous malformations and associated aneurysms
TRANSCRIPT
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Perspectives
Robert F. Spetzler, M.D.
Director, Barrow Neurological Institute (BNI)J. N. Harber Chair of Neurological Surgery at BNI
Chairman and President, Barrow Neurosurgical Associates, Professor of SurgerySection of Neurosurgery, University of Arizona College of Medicine
Arteriovenous Malformations and Associated Aneurysms
Commentary on:Cerebral Arteriovenous MalformationsAssociated with Flow-Related and Circle ofWillis Aneurysmsby Lv et al. pp. 455-458.
Kaith Almefty and Robert F. Spetzler
A rteriovenous malformations (AVMs) of the brain oftenpresent complex management decisions for the treatingsurgeon. The surgical treatment of these lesions is
ntended to eliminate the risks of intracranial hemorrhage; how-ver, eliminating this risk must be balanced by the risks andorbidity and mortality associated with treating the lesion.atural history studies have provided the basis for assessing the
isk of hemorrhage and associated morbidity of untreated AVMs.he annual risk of intracranial hemorrhage associated with anntreated AVM is 2%-3% per year; the risk of recurrent hemor-hage is even greater. The risk of death in the event of hemor-hage is approximately 10%, and the risk of a neurologic deficit ispproximately 50% (8).
n 1986, the Spetzler-Martin grading scale was introduced to helpurgeons make the complex decisions on how to manage theseesions (8). Recently, the scale was simplified into a 3-tier gradingcale (9). At the Barrow Neurological Institute, the managementf AVMs follows a treatment paradigm whereby Class A (previ-usly grades I and II) lesions are managed with surgical resection.lass C (grades IV and V) AVMs are treated conservatively. Otheruthors, such as de Oliveira et al. (2) and Lawton (4) haveuggested that Class B (Grade III) lesions be further subclassifiednd proposed management strategies for their subclasses. deliveira et al. (2) reclassified Grade III AVMs into Grade IIIA (large)nd IIIB (small, in eloquent areas) lesions and proposed emboli-ation plus surgery for the IIIA and radiosurgery for IIIB AVMs.awton (4) recommended surgery for small, eloquent AVMs witheep drainage (size [S1], eloquence [E1], deep venous drainageV1]), conservative treatment for larger lesions without deeprainage (S2, E1, V0), and “judicious” selection for his interme-iate group (S2, E0, V1). We also have found this class of lesionso be complex and heterogeneous, typically requiring a multimo-
Key words� Arteriovenous malformation� Cerebral aneurysm
Abbreviations and AcronymsAVM: Arteriovenous malformations
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dality approach with the use of microsurgical, endovascular, andradiosurgical techniques.
Although the grading scales offer surgeons guidance for makingthese complex treatment decisions, each AVM is unique andshould be considered individually. Features such as the numberand distribution of feeding arteries, previous hemorrhages, thepatient’s neurologic status, the amount of flow through thelesion, the degree of vascular steal from surrounding brain, andthe number and location of associated aneurysms should beconsidered. A grading scheme that encompassed all of thesefeatures would be cumbersome and impractical. Many of thefactors, however, are interrelated and thus are often capturedindirectly in the grading schemes.
The association of aneurysms in patients with AVMs is welldocumented with a reported incidence between 10% and 58%.It is also well demonstrated that an additional risk of intracranialhemorrhage is present in AVM patients with aneurysms. Re-dekop et al. (7) classified these aneurysms as either intranidal,flow-related, or unrelated to the AVM nidus. In patients withintranidal aneurysms, this group found a 10% risk of hemorrhageper year, which is considerably greater than the 2%-4% annualhemorrhage rate usually attributed to AVMs.
Given the increased risk associated with AVM-associatedaneurysms, some authors have suggested aggressive man-agement strategies. The belief that hemodynamic changesassociated with the abrupt elimination of AVMs may place theassociated aneurysm at a greater risk of rupture led Batjer etal. (1) to recommend treatment of the aneurysm beforepursuing resection of the AVM. Thompson et al. (10) alsorecommended a management protocol designed to treat theaneurysms by surgical or endovascular means before admin-istering definitive therapy for the AVM.
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’sHospital and Medical Center, Phoenix, Arizona, USA
To whom corresponding should be addressed: Robert F. Spetzler, M.D.[E-mail: [email protected]]
Citation: World Neurosurg. (2011) 76, 5:396-397.DOI: 10.1016/j.wneu.2011.06.051
RLD NEUROSURGERY, DOI:10.1016/j.wneu.2011.06.051
afi
PERSPECTIVES
However, Redekop et al. (7) noted regression of 80% of distalnd of 17% of proximal aneurysms after treatment of the AVMrst. Meisel et al. (6) reported on 305 AVMs with associated
aneurysms and suggested that intranidal aneurysms should beprimary treatment targets whereas proximal aneurysms shouldnot. Their rationale was based on evidence that the latter oftenregress after definitive AVM treatment and on their finding thatproximal aneurysms were not associated with the same increasein hemorrhage rate as intranidal aneurysms. Redekop et al. (6)and Meisel et al. (7) presented good evidence for the treatmentof intranidal aneurysms and observation of proximal aneurysms.
It is our paradigm that the symptomatic lesion be treated. Inthe event of intracranial hemorrhage, an attempt to identifythe causative lesion and treatment should be directed at thatlesion. We have traditionally regarded associated aneurysmsas independent risk factors and treated them aggressively. Forproximal aneurysms the decision is based on size, as withgeneral aneurysm treatment, and small proximal aneurysmsare followed while larger proximal aneurysms treated directly.We have advocated that Grade IV and V AVMs be managedconservatively (3). However, in the presence of associatedaneurysms, we believe that the aneurysm should be treateddirectly without intervention to the AVM, given the highmorbidity associated with treating the AVM primarily. Further-more, we do not recommend partial treatment of high-gradeAVMs except in the case of a progressive neurologic deficit
related to vascular steal (3).ification of the grading scale. Neurosurgery 52:740-748, 2003.
for arteriovenous malform476-483, 1986.
WORLD NEUROSURGERY 76 [5]: 396-397, NOVEMBER 2011
In the present paper, Lv et al. (5) retrospectively reviewed 302patients treated with AVMs at their institution. Their large seriescovers the important topic of risk of rupture in AVMs that havehigh-risk features such as associated aneurysms. In this series,an intranidal-associated aneurysm was present in 13.6% of theircases, and extranidal aneurysms were present in 10.9%. Theauthors suggested that AVM-associated aneurysms be classifiedas either circle of Willis or flow related. They further suggestedthat circle of Willis aneurysms be managed in a fashion similar tothe general treatment of aneurysms. They found that aneurysmswere more often associated with AVMs that became symptom-atic with hemorrhage, older patients, and infratentorial lesions. Intheir series, flow-related aneurysms were not associated withsignificantly more intracranial hemorrhages than circle of Willisaneurysms. However, circle of Willis aneurysms had a greaterincidence of subarachnoid hemorrhage. This finding suggeststhat circle of Willis aneurysms should be treated primarily.
The appropriate management of AVMs remains complex, andthis study is an additional resource to the growing literature onthe incidence and risks of AVM-associated aneurysms. Specifi-cally, Class B AVMs continue to challenge surgeons with difficulttreatment decisions. Indeed, four questions await clear andconclusive answers. First, what is the extent of risk attributableto “high-risk” features such as associated aneurysms? Second,which subtypes of these aneurysms are associated with thegreatest risk of hemorrhage? Third, what is the true pathogenesisof these aneurysms? And finally, which modality is most effec-
tive for their treatment?1
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REFERENCES
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itation: World Neurosurg. (2011) 76, 5:396-397.OI: 10.1016/j.wneu.2011.06.051
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