The Pathology of Vascular (“Arteriovenous”) Malformations

V ASCULAR malformations of the central nervous system have been known for at least three hundred years (Olivecrona and Ladenheim '57), hu t are still surrounded by considerable confusion and associated with a complex classification. Detailed morphologic studies of large numbers of cases are rare. Reviews of the many classifications can be found the works of Evans and Courville '39, Noran '45, Olivecrona and Ladenheim '57, and Rayno r and Kingman '65. While the relationship of vascular malformations to vascular neoplasms is still less than completely clear (Raynor and Kingman '65), it seems relatively certain tha t arteriovenous malformations are true developmental malformations and not neoplasms (Wolf and Brock '35, Noran '45, Manuelidis '50, Olivecrona and Ladenheim '57, Zttlch '57, Russell and Rubinstein '59, Bailey '61, Kaplan et al. '61, McCormick and Nofzinger '66). Ztilch '57 states tha t the distinction between vascular malformations and vascular neoplasms is difficult, and distinguishes between the two groups on the basis of the autonomous growth seen the la t ter group. However , as Russell and Rubinstein '59 and others have noted, in common with the t rue neoplasms, it is clear tha t some malformations at least are not static bu t grow and inflict progressive destruct ion on the adjacent bra . Noran '45 considered tha t the presence of brain parenchyma between the vessels of the angioma was of pa ramoun t impor tance concluding tha t it is a malformat ion ra ther than a vascular neoplasm. Clearly, however, this does not hold for all malformations, most notably the cavernous angiomas. In spite of these difficulties, one considers the malformations to be distinct from the t rue