RTERIOVENOUS malformations (AVMs) of the brain are congenital lesions characterized by abnormal direct arteriovenous communications without an intervening capillary bed. 20 They are believed to form at approximately 3 weeks of gestation due to an arrest in the normal development of primitive arteries, capillaries, and veins. With time, additional arterial contributions are acquired, resulting in increased blood flow and, typically, repeated hemorrhages. 29 On angiography, AVMs can be seen to have multiple tortuous arterial feeders and one or more dilated draining venous channels. 29 Magnetic reso- nance (MR) imaging most often demonstrates signal voids within these enlarged high-flow vascular structures, as well as other signal intensity abnormalities in regions of thrombosis, local hemorrhage, and parenchymal changes. 1 Treatment options include surgical excision, endovascu- lar embolization for devascularization, and local radio- surgery. Clinical outcome following surgical or endovascular in- tervention is related to many characteristics of the lesion, including nidus size and venous drainage of the AVM as well as to the proximity of the lesion to eloquent cor- tex. 28,30 Although conventional imaging techniques such as MR can exquisitely determine the relationship to ana- tomically defined regions of important cortex (such as pre- and postcentral gyri), they do not establish the rela- tionship to functional cortex, particularly for such com- plex functions as language. Such information may be of value in planning surgical approach or the extent of at- tempted endovascular ablation. 11,17 Moreover, the strictly anatomical localization provided by conventional MR im- aging does not take into account the plasticity of brain function, which at least in theory could be relevant, given the congenital nature of the lesion as well as the associat- ed parenchymal insults from hemorrhage and ischemia. Blood oxygen level–dependent contrast (BOLD) imag- ing 21,22 is a noninvasive functional MR imaging technique for localizing regional brain signal intensity changes in response to task performance. 4,23,31 This technique uses no J. Neurosurg. / Volume 84 / March, 1996 J Neurosurg 84:477–483, 1996 Functional magnetic resonance imaging of regional brain activity in patients with intracerebral arteriovenous malformations before surgical or endovascular therapy JOSEPH MALDJIAN, M.D., SCOTT W. A TLAS, M.D., ROBERT S. HOWARD II, M.D., ELIZABETH GREENSTEIN, M.D., DAVID ALSOP , PH.D., JOHN A. DETRE, M.D., JOHN LISTERUD, M.D., PH.D., MARK D’ESPOSITO, M.D., AND EUGENE S. FLAMM, M.D. Departments of Radiology, Neurology, and Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania U Functional magnetic resonance (MR) imaging was performed in six patients harboring proven intracerebral arte- riovenous malformations (AVMs) using a noninvasive blood oxygen level–dependent technique based on the docu- mented discrepancy between regional increases in blood flow and oxygen utilization in response to regional brain acti- vation. Statistical functional MR maps were generated and overlaid directly onto conventional MR images obtained at the same session. In the six patients studied, a total of 23 separate functional MR imaging activation studies were per- formed. Of these, two runs were discarded because of motion artifacts. All of the remaining 21 studies demonstrated activation in or near expected regions for the paradigm employed. Qualitatively reproducible regional localizations of functional activity in unexpected sites were also seen. The authors’ findings indicating aberrant mapping of cortical function may be explained on the basis of the plasticity of brain function, in that the developing brain can take over function that would normally have been performed by regions of brain encompassed by the lesion. Preliminary results in this study’s small number of cases also indicate that activity demonstrated within the confines of the apparent AVM nidus may help predict the development of a posttherapy deficit. The authors demonstrate that functional MR imaging can be successfully and reproducibly performed in patients with intracerebral AVMs. Notwithstanding the paucity of normative data using functional MR imaging, the authors’ findings support cortical reorganization associated with these congenital lesions. Blood oxygen level–dependent MR imaging is a noninvasive method used to localize areas of eloquent cortex in patients harboring AVMs; it may prove to be of value in treatment planning. KEY WORDS • arteriovenous malformation • magnetic resonance imaging • vascular malformation • functional magnetic resonance imaging A 477