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...

SUMMARY:Transarterial embolization in the external carotid artery (ECA) territory has a major role in the endovascular management of epistaxis, skull base tumors, and dural arteriovenous fistulas. Knowledge of the potential anastomotic routes, identification of the cranial nerve supply from the ECA, and the proper choice of embolic material are crucial to help the interventionalist avoid neurologic complications during the procedure. Three regions along the skull base constitute potential anastomotic routes between the extracranial and intracranial arteries: the orbital, the petrocavernous, and the upper cervical regions. Branches of the internal maxillary artery have anastomoses with the ophthalmic artery and petrocavernous internal carotid artery (ICA), whereas the branches of the ascending pharyngeal artery are connected to the petrocavernous ICA. Branches of both the ascending pharyngeal artery and the occipital artery have anastomoses with the vertebral artery. To avoid cranial nerve palsy, one must have knowledge of the supply to the lower cranial nerves: The petrous branch of the middle meningeal artery and the stylomastoid branch of the posterior auricular artery form the facial arcade as the major supply to the facial nerve, and the neuromeningeal trunk of the ascending pharyngeal artery supplies the lower cranial nerves (CN IXϪXII).

Background and Purpose-Although it is generally accepted that developmental venous anomalies (DVAs) are benign vascular malformations, over the past years, we have seen patients with symptomatic DVAs. Therefore, we performed a retrospective study and a literature study to review how, when, and why DVAs can become clinically significant. Methods-Charts and angiographic films of 17 patients with DVAs whose 18 vascular symptoms could be attributed to a DVA were selected from a neurovascular databank of our hospital. MRI had to be available to rule out any other associated disease. In the literature, 51 cases of well-documented symptomatic DVAs were found. Pathomechanisms were divided into mechanical and flow-related causes. Results-Mechanical (obstructive or compressive) pathomechanisms accounted for 14 of 69 symptomatic patients resulting in hydrocephalus or nerve compression syndromes. Flow-related pathomechanisms (49 of 69 patients) could be subdivided into complications resulting from an increase of flow into the DVA (owing to an arteriovenous shunt using the DVA as the drainage route; nϭ19) or a decrease of outflow (nϭ26) or a remote shunt with increased venous pressure (nϭ4) leading to symptoms of venous congestion. In 6 cases, no specific pathomechanisms were detected. Conclusions-Although DVAs should be considered benign, under rare circumstances, they can be symptomatic. DVAs, as extreme variations of normal venous drainage, may represent a more fragile venous drainage system that can be more easily affected by in-and outflow alterations. The integrity of the DVA needs to be preserved irrespective of the treatment that should be tailored to the specific pathomechanism. (Stroke. 2008;39:3201-3215.)