A New Type of Spinal Epidural Arteriovenous Fistulas Causes Spinal Epidural Hemorrhage: An Analysis of Five Cases and Natural History Consideration.

Background: Spinal epidural arteriovenous fistulas (SEDAVFs) are peculiar and poorly understood lesions with a poorly understood natural history. They usually are subclassified into 2 types according to their drainage components. This study aimed to describe a new type of SEDAVFs that is featured with a unique drainage pattern and present our natural history hypothesis of SEDAVFs.

Methods: Five SEDAVF cases of the new type were reviewed retrospectively from a high case-volume spinal vascular malformation database. The clinical manifestations, neuroradiologic findings, angioarchitecture, treatment strategies, and clinical outcomes were assessed.

Results: All patients presented with spontaneous spinal epidural hematoma, and 2 of them exhibited rebleeding. The median age at the initial episode was 20 years. Spinal digital subtraction angiography revealed slow-flow epidural fistulas drained by spinal epidural venous plexus without intradural drainage or engorged venous pouches in all 5 patients. Three patients underwent microsurgical treatment. The outcomes of all of the patients were favorable.

Conclusions: Our study reported a special type of hemorrhagic SEDAVF without an intradural drainage component or epidural mass effect. The key diagnostic clue was early opacification of spinal epidural venous plexus on spinal angiogram. We believe SEDAVFs may form at an early age and gradually develop with time. Different types of SEDAVFs may represent different developing stages of one disease, and our type may represent the early stage of SEDAVFs.