Paracondylar process combined with persistent first intersegmental vertebral artery: an anatomic case report and literature review.

The paracondylar process (PCP) and the persistent first intersegmental vertebral artery (PFIA) are both rare variations at the craniovertebral junction. We report the above two variations coexisting in one cadaveric head during the training of far lateral approach in our skull base lab. The specimen simultaneously had a left occipitalized atlas associated with a PFIA and a right PCP. The previous reports, the embryogenesis, and the clinical implications of the two variations were also reviewed. Preoperative recognition of the rare variations is essential to a safe far lateral approach.