The vertebral artery (VA) undergoes a critical anatomical transition as it pierces the dura mater at the craniocervical junction. Precise knowledge of dural penetration patterns and angulation is essential for diagnostic imaging, neurosurgical planning, and minimizing iatrogenic risk in posterior fossa procedures.

This retrospective imaging study evaluated 100 adult patients who underwent 1.5 Tesla magnetic resonance angiography (MRA) with a time-of-flight protocol. The site of VA dural penetration was categorized on axial images as ventral, middle, or dorsal, and on coronal images as symmetrical (Type A) or asymmetrical (Types B or C). Angulations at the point of dural entry were quantified in axial and coronal planes. Documented vascular variants included extradural origins of the posterior inferior cerebellar artery (PICA) and aberrant VA trajectories.

Middle axial penetration was the most frequent pattern (87 % of sides), while symmetrical coronal entry (Type A) predominated in 77 % of patients. Axial VA angulation differed significantly by sex (p = 0.034), with females exhibiting sharper angles. No side-related differences were observed for angulation or penetration type. Extradural PICA origin and aberrant VA course were identified in 16.5 % and 6 % of sides, respectively, but did not correlate with dural entry patterns.

The VA exhibits a highly consistent trajectory at the dura, most commonly entering at the middle axial zone with symmetrical coronal configuration. A sex-related difference in axial angulation may have biomechanical and hemodynamic implications. Although vascular variants are relatively common, they do not appear to influence penetration type yet remain relevant for surgical safety and diagnostic accuracy.