Functional Evaluation of Arteriovenous Malformations

Nicholas C. Bambakidis, M.D., Jeffrey L. Sunshine, M.D., Ph.D., Peter F. Faulhaber, M.D., Rober W. Tarr, M.D., Warren R. Selman, M.D., Robert A. Ratcheson, M.D., Departments of Radiology and Neurosurgery, Case Western Reserve University School of Medicine, Cleveland; and University Hospitals of Cleveland, Cleveland, Ohio

Neurosurg Focus. 2001;11(5) 

In This Article

Abstract and Introduction

Detailed knowledge of the angioarchitecture of arteriovenous malformations (AVMs) is necessary in determining the optimal timing and method of treatment of these challenging lesions. Many techniques are available for studying the functionality of surrounding cortical structures of AVMs. These include the use of positron emission tomography, functional magnetic resonance imaging, magnetoencephalography, and direct provocative testing of cortical function. The use of these methods to determine flow dynamics and tissue perfusion is also reviewed. These techniques are discussed in the present study, and their judicious utilization will enhance the safety of AVM therapy.

Defined as abnormal collections of blood vessels characterized by abnormal shunting of blood directly from an arterial supply to venous structures without an intervening capillary bed, AVMs present clinicians with many challenging scenarios given their complex nature and varied locations. Because they can arise in nearly any area of the brain, treatment strategies must take into account both the direct effects of the AVM on surrounding structures as well as the dependence of these structures on its blood supply. Clearly then, measures of the functionality of adjacent neural structures are critical in risk assessment when deciding when and how best to treat these lesions in individual patients.

Although AVMs can cause symptoms due to their epileptogenicity, mass effect, or ischemia, by far the most common presentation of a patient harboring one of these lesions is with an intracranial hemorrhage. A 24-year retrospective analysis of 166 symptomatic patients by Ondra, et al.,[19] who estimated the average risk of major bleeding to be 4% per year, with a mean interval of 7.7 years between hemorrhages and a morbidity and mortality rate of 2.7% per year. There has also been evidence presented that small AVMs present with hemorrhage more frequently than larger ones, a fact that may be related to higher pressure in the smaller feeding arteries.[1,12,24] In determining the appropriate treatment strategies in an individual patient, clinicians must take into account factors such as the pattern of venous drainage and arterial supply and the presence of critical surrounding neural structures. Although surgical resection continues to be the treatment modality of choice, alternatives such as stereotactic radio-surgery and embolization must be considered. To better estimate surgical risk clinicians can use several methods that aid in the evaluation of local blood flow and cerebral function.