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Spinal and Paraspinal Arteriovenous Lesions.

Vascular lesions of the spine and spinal cord can be categorized into intramedullary and extramedullary lesions. These lesions are rare and comprise a heterogeneous spectrum of diseases. They were first reported in the 19th century with the autopsy-based classification of Virchow and Picard. However, it was in the 1970s, with the advent of selective spinal angiography, that they became better understood; thanks to the descriptions of Djindjian and Kricheff, Aminoff and Logue, and Di Chiro and Wener. Their identification and localization have progressed significantly with the development of imaging techniques. Several classification systems have been proposed over time to describe vascular lesions of the spine. One of the classifications, from the Bicêtre group, categorizes spinal arteriovenous shunts (AVSs) according to their genetic and developmental features, distinguishing genetic hereditary lesions (type I), genetic nonhereditary lesions (type II), and focal (sporadic) lesions (type III). Although comprehensive, this classification is not widely used in clinical practice as most spinal AVSs belong to the third group, while a precise stratification of focal or sporadic lesions is necessary for the clinical and therapeutical management of the patients. In addition, recent studies have shown somatic activating mutations in the KRAS pathway in brain arteriovenous malformations (AVMs), opening new horizons in understanding the genetic patterns of arteriovenous lesions, particularly the nonhereditary and focal ones. Spetzler et al proposed a broader classification based on the type of vascular malformation and included neoplastic lesions, cavernomas, spinal aneurysms, arteriovenous fistula (AVF), and AVM. However, spinal AVS lesions share common pathophysiological mechanisms and clinical presentations, whereas nonshunting vascular lesions with a venous phenotype such as telangiectasias and cavernomas, as well as vascular tumors and idiopathic spinal artery aneurysms, represent different diseases with specific pathophysiology. Here, we focus only on the spinal AVS lesions and propose a systematic classification based on their anatomic relationship with the spinal cord and surrounding spinal structures. A brief introduction to the vascular anatomy of the spinal cord is detailed in the online-only Data Supplement.