Topographic Localization of Cerebrospinal Fluid-Venous Fistulae

Transvenous embolization (TVE) is an effective treatment for cerebrospinal fluid-venous fistulae (CVFs) causing spontaneous intracranial hypotension. During TVE the precise site of intrathecal-intravascular fistulization is not visualized; the standard approach entails extensive embolic casting to improve the likelihood of CVF obliteration. We sought to define the imaging-based location of the fistulous point relative to the intervertebral foramen and to determine whether foraminal topography differs by CVF morphology.

We retrospectively reviewed 29 consecutive patients with CVF-positive CT myelography. CVFs were classified as diverticular or non-diverticular based on whether the draining vein originated from a meningeal diverticulum. The visualized fistulous point (origin of the draining vein on CT myelography) was mapped onto a standardized foraminal schematic to characterize its distribution in 3 planes.

Meningeal diverticula at the CVF level were present in 24/29 (82.8%) cases. Fourteen (48.3%) CVFs were diverticular and 15 (51.7%) were non-diverticular. In the axial plane, diverticular CVFs most frequently localized to the ventrolateral foramen (10/14, 71.4%), whereas non-diverticular CVFs most frequently localized to the ventromedial foramen (9/15, 60%) (p=.001). In the sagittal plane, most fistulous points (69.0%) localized to the anterosuperior foraminal quadrant; this distribution did not differ by CVF type (p=.96). In non-diverticular CVFs, the fistulous point was located along the normal-appearing nerve root sleeve (8/15, 53.3%) or on the spinal canal dura (7/15, 46.7%).

CVFs demonstrate a reproducible foraminal topography on CT myelography that varies by morphology: diverticular fistulae more often localize ventrolaterally, whereas non-diverticular fistulae favor ventromedial locations. Across types, fistulous points most commonly lie in the anterosuperior foraminal quadrant. These imaging landmarks may help inform procedural targeting during TVE and transforaminal fibrin glue injection.