Venous structures can mimic masses in the foramen magnum

Benign enhancing lesions at the foramen magnum is a recently described entity and believed to represent a varix or ganglion. These lesions are typically described as being single, located posterior to the intradural vertebral artery, and not attached to the dura. These 2 cases demonstrate previously undescribed variations in appearance of these lesions including contacting the posterior inferior cerebellar artery and lateral epidural plexus/dura, segmental dilatations, transverse and linear configuration, and visualization on an unenhanced CT head. These lesions most likely reflect bridging veins and are structures that clinicians should be aware of to avoid unnecessary follow-up or surgical intervention.