Clinical Imaging Exam 1 Practice 2026 – The Comprehensive All-in-One Guide to Master Your Exam!

Hahn's venous cleft reflects a prominent venous channel in the epidural space, an anatomic variant caused by enlargement of the anterior epidural venous plexus that can fill with contrast or appear on imaging as a cleft in front of the thecal sac. It is most conspicuous in the lower thoracic spine because this region has the largest and most conspicuous epidural venous plexus with drainage patterns that favor venous filling when contrast is present. The combination of a relatively compact thecal sac and prominent venous channels here makes the venous cleft most detectable between roughly the mid to lower thoracic levels. In cervical, upper thoracic, or lumbar regions the venous plexus is less prominent on routine imaging, so Hahn's venous cleft is not as readily seen there. This is a benign variant and helps explain a midline venous channel seen on imaging without implying a disc or mass lesion.