Early Occipitocervical Fusion Surgery in a Rare Clinical Encounter of Non-traumatic Atlantooccipital Subluxation (AOS) in Down Syndrome (Trisomy 21)

Abstract

Subluxation of the atlantooccipital joint in patients with underlying Down syndrome is an extremely rare orthopedic condition. The condition can pose life-threatening risks if not promptly diagnosed and treated in the early stage. Yet, there have been documented cases of survival following atlantooccipital subluxation or dislocation. Atlantooccipital subluxation (AOS) is usually identified during screening in children with Down syndrome for atlantoaxial subluxation (AAS). Therefore, careful evaluation of the atlantooccipital joint from radiographs is also essential. It is crucial to emphasize the clinical significance of AOS. Here the authors present the case of a fifteen-year-old girl with underlying Down syndrome (trisomy 21) who survived a sudden onset of non-traumatic atlantooccipital subluxation with spinal cord compression. There are only a few cases were reported in patients with Down syndrome (trisomy 21) and only two cases with surgically treated atlantooccipital (C0C1) subluxation have been reported. This case is of particular interest as it represents the first reported case of atlantooccipital (C0C1) subluxation with spinal cord compression in Down syndrome that underwent occipitocervical fusion surgery during the acute presentation, resulting in significant neurological recovery. Her neurology symptoms and physical functions showed remarkable improvement post-surgery, and she is doing well at the one-year follow-up in the clinic. Early surgery during acute presentation in this case resulted in good surgical outcomes and improved patient quality of life.

Keywords: atlanto-axial subluxation; atlanto-occipital c2-c3 fusion; cervical spine alignment; cervical spine anomalies; down's syndrome; occipito-cervical fusion surgery; pediatric cervical spine; pediatric spine surgery; spine and pediatrics orthopedics; trisomy of 21.

Figure 1. Preoperative lateral view of cervical x-ray for the patient.

The x-ray showed subluxation of the atlantooccipital joint (arrow).

Figure 2. Comparison of lateral view cervical x-ray of the patient in neutral (B), flexion (C), and extension (D) with the ideally normal x-ray (A).

Extension and neutral views show atlantooccipital subluxation (AOS). Flexion view shows partial reduction of AOS.

Figure 3. The patient was carefully transferred for imaging investigation with the floppy neck.

Figure 4. The patient’s CT scan showed a widening of the basion-dens interval (BDI) with vertical dissociation in neutral (B), flexion (C), and extension (D) views compared to normal one (A).

Figure 5. Post-reduction C2 aligned to external occipital protuberance.

Figure 6. Posterior fusion occiput to C2 and C3.

Figure 7. Cranio-cervical alignment restored post-fusion surgery.

Figure 8. The patient demonstrated good neurological recovery and healed surgical scar during the one-year follow-up.

The patient was able to drink by herself (A) and ambulate well without aid (B). No more floppy neck seen. The surgical scar was completely healed (C).

Figure 9. One-year follow-up cervical radiograph revealed that implants were in situ with no signs of loosening and the cranio-cervical alignment was well maintained.

Lateral view (A) and anteroposterior view (B) of the cervical radiograph.