Given the task definition and input, reply with output. Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: We report a rare case of supra- and infratentorial arteriovenous malformations (AVMs), which were separate and consisted of aneurysmal dilations with two or three afferent arteries and efferent veins. Surgical resections were performed without the occurrence of additional neurological deficits. We discuss the treatment of multiple AVMs and stress that size and the structures involved are more important factors in the prognosis than the multiplicity of the lesions.
Arteriovenous Malformations