Surgical treatment of headshaking by removal of a paracondylar process fragment via modified hyovertebrotomy approach: A detailed anatomical and surgical description in an adult horse.

Objective: To describe, in detail, the relevant anatomy and surgical approach to access the paracondylar process (PCP) and report its application in a clinical case of headshaking.

Animal: A seven-year-old, mixed breed mare.

Study Design: Experimental study/case report.

Methods: A seven-year-old mixed breed mare was presented for investigation of acute onset progressing violent headshaking, resulting in the horse falling on multiple occasions. The horse was highly reactive to palpation over the right PCP. Standing computed tomographic (CT) investigation and ultrasonographic examination of the head detected a fracture of the right PCP. Five equine heads of mixed breeds and sizes were dissected to demonstrate the relevant anatomy surrounding the PCP with regard to surgical access. A modified hyovertebrotomy approach was used to remove the fracture fragment under general anesthesia.

Results: The anatomy surrounding the PCP was described. The fragment was successfully removed resulting in gradual resolution of clinical signs. The horse recovered well postoperatively and was back into light levels of work with no signs of headshaking present two and a half years following surgery.

Conclusion: The caudal meningeal artery and vein as well as the glossopharyngeal and hypoglossal nerves are adjacent to the PCP and must be avoided during dissections. The modified hyovertebrotomy approach allows safe surgical access to the PCP. Surgical excision of a PCP fragment can result in complete resolution of clinical signs of headshaking. Computed tomography and ultrasonography are valuable diagnostic tools to identify a fracture of the PCP.