Extraforaminal Vertebral Artery Until C2 Transverse Foramen in Down Syndrome Patient Affected by Atlantoaxial Subluxation: First Observation and Review of Literature.

Abstract

Patients with Down syndrome (DS) have an increased incidence of multisystem disorders, like cardiovascular, neurologic, gastrointestinal, respiratory, and musculoskeletal disorders. Craniovertebral junction instability is a common illness in DS patients, and they may often be affected by vertebral artery (VA) anomalies. In this paper we present neuroradiologic findings of a 34-year-old female patient affected by DS with atlantoaxial subluxation, scheduled for transoral decompression of C1-C2 and posterior occipitocervical fixation. The preoperative angio-computed tomography scan showed a peculiar anatomic variation in the entrance of the VA at the level of the C2 transverse foramen (TF). Normally, the segment of VA, named V2, becomes intraforaminal on average at the TF of C6. We reviewed the literature about the incidence of anatomic variations of the V2 segment in both the general population and the one affected by DS, and although numerous cases of anomalous course, none reported a C2 TF entry point. Ignoring such extremely rare anatomic variation during anterior, posterior, or lateral surgical approach to the cervical spine can lead to inadvertent injury and potentially serious complications like arterial dissection, thrombus, vascular spasm, fistula, pseudoaneurysm, cerebral ischemia, and death.