A prevalence study of the axiobasilaris muscle.

Axiobasilaris is an accessory muscle of the prevertebral region. While historical cases have been described in the late 19th century, to our knowledge, no new reports of this muscular variation have been published since that time period. Visual representation of axiobasilaris is also lacking aside from illustrations produced in 1880 by Gruber. Recording anatomical variations is valuable for both teaching and clinical practice, as variations may be encountered by anatomists in the dissection laboratory and cause implications in the surgical setting. Prevertebral variations such as axiobasilaris are relevant in cases of endoscopic endonasal skull base surgery, trans-oral release and reduction of the cervical spine, as well as cervical corpectomy. From a functional perspective, axiobasilaris is thought to contribute to flexion at the atlanto-occipital and atlanto-axial joints. This study aims to determine the prevalence of axiobasilaris through the dissection of 60 donor cadavers (120 sides). Axiobasilaris was found in five out of the 60 (8.33%) donors dissected in this study; two cases presented as a single unilateral muscle, while three others presented as paired bilateral muscles for a total of eight out of 120 sides (6.67%).