Spinal Dural Arteriovenous Fistulas

Abstract

SUMMARY:Spinal dural arteriovenous (AV) fistulas are the most commonly encountered vascular malformation of the spinal cord and a treatable cause for progressive para-or tetraplegia. They most commonly affect elderly men and are classically found in the thoracolumbar region. The AV shunt is located inside the dura mater close to the spinal nerve root where the arterial blood from a radiculomeningeal artery enters a radicular vein. The increase in spinal venous pressure leads to decreased drainage of normal spinal veins, venous congestion, and the clinical findings of progressive myelopathy. On MR imaging, the combination of cord edema, perimedullary dilated vessels, and cord enhancement is characteristic. Therapy has to be aimed at occluding the shunting zone, either by superselective embolization with a liquid embolic agent or by a neurosurgical approach. Following occlusion of the fistula, the progression of the disease can be stopped and improvement of symptoms is typically observed. Despite being the most commonly encountered spinal vascular malformation, spinal dural arteriovenous fistulas (SDAVFs) are rare and still underdiagnosed entities, which, if not treated properly, can lead to considerable morbidity with progressive spinal cord symptoms. Because presenting clinical symptoms are unspecific, the neuroradiologist is often the first clinician to raise the possibility of this diagnosis, which initially rests mainly on MR imaging. For a thorough understanding of the disease and for planning the therapeutic strategy, however, selective spinal digital subtraction angiography (DSA) still is necessary. The aim of the following article is to review the epidemiology, etiology, clinical and imaging features, and therapeutic approaches of this type of spinal vascular malformation. Because an understanding of spinal vascular malformations both from an etiologic and pathophysiologic standpoint is based on the spinal vascular anatomy, we will start by briefly describing the salient features of the spine and spinal cord arterial supply and venous drainage followed by a classification of spinal vascular malformations in general and a classification of dural arteriovenous (AV) shunts in particular. Embryology and Anatomy of the Spinal VasculatureDevelopment of the neural plate starts during the third gestational week and is derived from the embryologic ectoderm. This process is induced by the underlying notochord and adjacent mesoderm, which regulate the development of the surrounding structures, including the nerves, blood vessels, and somites.1 In this stage, the angioblasts initially form small cell clusters (blood islands) within the embryonic and extraembryonic mesoderm.2 Formation of the neural tube begins early in the fourth week (days 22-23) with closure of the rostral and caudal neuropore during days 25-27, which coincides with the establishment of the intrinsic blood vascular circulation within the spinal cord.3 Two longitudinal collector systems form in the subarachnoid space at the dorsal and ventral surfac...

Spinal Dural Arteriovenous Fistulas: Clinical and Radiological outcome of Endovascular Treatment

“…SDAVFs are relatively rare, and their diagnosis is often missed because of nonspecific clinical symptoms at presentation. 12,13,19 The delay to diagnosis in our patients 23.9 months (range, 6-36 months) is comparable to other series. 11,13,14,23 We did not correlate the severity of the clinical presentation with the time of diagnosis.…”

“…Most of the patients in our study were males 77.3% (17 patients) with an average age of 59.3± 9.7.This finding also correlates with the demographics seen in several other large studies. 14,19,23 We had only one patient younger than 40 years in our study, which illustrates the rarity of this diagnosis in the younger patient population.…”

Spinal Dural Arteriovenous Fistulas Supplied from Multiple Segmental Arteries: Microsurgery Using Indocyanine Green Angiography and Radiosurgery with a Spine Tracking System

“…Symptoms in Group 2 appear suddenly, with epidural hematoma formation, and progressively in Group 3 as a result of abnormal drainage (flow reversal) into the perimedullary veins. In Group 1, symptoms develop slowly due to compression of the spinal cord and/or nerve roots by enlarged epidural venous pouches [1]. Treatment with endovascular occlusion and/or surgical disconnection of fistulas is required in patients with acute or rapidly progressive symptoms before the spinal cord damage becomes irreversible [2][3][4].…”

Microvascular anatomy of spinal dural arteriovenous fistulas: arteriovenous connections and their relationships with the dura mater

“…Obtaining and assessing these small specimens is also challenging in practice. Furthermore, because spinal dural AVFs are increasingly being treated by endovascular embolization, 14,15,17 opportunities to observe with direct microscopy and obtain surgical specimens of these lesions are fewer.…”

“…Spinal dural AVFs have been attributed to a direct abnormal arteriovenous (AV) connection between a meningeal branch of a segmental artery and intradural radiculomedullary vein without an intervening nidus. 4,14 The localization of a dural AVF to 1 spinal level and side can be visualized with angiography.…”