A 23 y.o. woman with Down's syndrome presented with headache and neck pain.

Why were physicians concerned after seeing her cervical spine films?

normal anatomy of C1,2

The concern in our patient was for an atlantoaxial subluxation  which is seen in 10-20% of Down’s patients. On the xray there was a subtle asymmetry of C1 on C2 on the coronal image.  If there is instability of the transverse  ligament it can cause a widening of the anterior odontoid-axial distance (AAOD)   and therefore a decrease in the posterior atlanto-odontoid distance (PAOD).  In 1-2% of Downs patients this causes spinal cord compression. Weakness of the transverse ligament can also cause rotational deformity.

This became news in 1983 when the Special Olympics prohibited Down’s individuals for participating in certain neck-stressing sports.

 50% of the motion of the neck occurs at C1,2 and they are held in anatomic position by  the transverse ligament which stabilizes the atlantoaxial joint and prevents anterior motion of the atlas on the axis and the alar ligaments, which pass from the posterolateral apex of the odontoid to the occipital processes, restricting  over-rotation

Atlanto axial subluxation can be diagnosed on cervical spine films  because of an abnormally large anterior atlanto-odontoid distance  or rotation noted on the coronal view.  The upper limit of the normal  anterior atlanto- odontoid distance is 4 mm in those younger than 15 and 3 mm in those older than 15. The space is greater in flexion than extension.  The cord requires a minimum space of 14 mm posterior to the dens. 14% of odontoid fractures have atlantoaxial instability.

While the diagnosis can be difficult to make; the patients usually present with neck pain and a tilt to the head caused by weakened ligaments and rotation of the lateral masses of C1 and C2

In rotatory dislocation the sternomastoid spasm is on the side of the chin, whereas in muscular torticollis the spasm is on the contralateral side.

Rheumatoid arthritis and other causes of ligamentous laxity like Down’s syndrome,, osteogenesis imperfecta, bony abnormalities,  Grisel’s syndrome, and trauma can cause this condition. Torticollis caused by a  pharyngotonsillitis or muscle spasm can mimic it in children.   A CT can generally rule it out but in the case of our patient; rotation of the head was thought to mimic the condition.  She was seen by neurosurgery who correctly diagnosed head rotation rather than an atlantoaxial subluxation.  She was treated for her headache and discharged home.

head tilt in rheumatoid arthritis caused by erosion the C 1,2 facets and atlantoaxial subluxation

TAKE HOME MESSAGE

Cervical spine trauma is reported to occur in 2.4% of blunt trauma victims.  In order to diagnose atlanto-axial rotatory subluxation you must maintain a high index of suspicion. 

trivia: rabbits have a condition causing head tilt, from an inner ear problem.

Barimani B, Fairag R, Abduljabbar F. et al. A missed traumatic atlanto-axial rotatory subluxation in an adult patient: case report. Case Report 2017 https://doi.org/10.2147/OAEM.S149296

Elhami F. Al-Busairi M, Al-Busairi W. et al. Cervical spine abnormalities associated with Down syndrome. Int Orthop. 2006 Aug;30(4):284-289.

Iqbal H, Mazzola C. Recurrent torticollis and cervical subluxation in a pediatric patient.  Science Repository.  2021. DOI 10.31487/j.SCR.2020.08.02.  

Goel A. Torticollis and rotatory atlantoaxial dislocation: a clinical review. 2019 J Craniovertebr Junctin Spine. Apri-Jun;10(2): 77-87.