Dural Arteriovenous Fistulas in Spontaneous Intracranial Hypotension.

The occurrence of dural arteriovenous fistulas (DAVFs) in patients with spontaneous intracranial hypotension (SIH) is exceptionally rare. While DAVF is a known complication of cerebral venous thrombosis (CVT), the role of CVT as one of the early events in the genesis of DAVFs is still debated. This is because only a small number of patients with CVT develop DAVFs, and not all DAVFs are associated with CVT. Although several hypotheses have been proposed to explain the link between CVT and DAVFs, the relationship between DAVFs and SIH in the absence of CVT remains unclear. To delineate the association between DAVFs and SIH. We reviewed the medical records of 460 SIH patients who were observed and treated over the past several years, looking specifically for cases of SIH complicated by DAVFs. We also reviewed all published case reports reporting patients with SIH and DAVFs. Of the 460 SIH patients reviewed, two (0.4%) were also diagnosed with DAVFs. Both patients had orthostatic headache, diffuse pachymeningeal enhancement, and brain sagging on brain magnetic resonance imaging, which are typical neuroimaging findings of SIH. Patient n.1 reported DAVF caused by left transverse/sigmoid sinus thrombosis, while patient n.2 presented DAVF as a complication of SIH in the absence of CVT. We speculate that SIH, even without CVT, might represent the start of a cascade of events leading to DAVFs. The pathogenic mechanism involved in DAVF formation in SIH patients could be explained by the opening of preexisting microscopic vascular channels within the dura mater, secondary to extreme venodilation related to SIH.