Atlanto-axial subluxation is a serious condition that can lead to paraplegia and death due to cervical cord compression. The upper cervical spine (C1–C2) is a complex articulation whose integrity is made up of bony and ligamentous structures. The bony structures include the combined anterior and posterior arches of C1 and the odontoid peg (dens of C2). The supporting ligaments are the transverse atlantal ligament, the paired alar ligaments and the apical ligament of the dens. Instability results from disruption or laxity of these ligaments and/or fractures of the dens or C1 arches.
Imaging of the C1–C2 articulation can be done with plain radiographs, CT or MRI. Plain radiographs are useful for delineation of bony alignment and for fractures, CT for patterns of bony destruction or fractures1
and MRI for spinal cord and nerve root evaluation. MRI can also help in delineating the ligaments.2
Atlanto-axial dislocation has several possible aetiologies. The more common causes include trauma,3
congenital defects4 5
and connective tissue disorders such as rheumatoid arthritis.6
Adjacent neck infections can be associated with laxity of the transverse atlantal ligament, particularly in children. In such cases this is referred to as Grisel's syndrome.7 8
Osteomyelitis is an uncommon entity in the cervical spine. It is more commonly noted in the thoracic spine in association with direct spread from chest infections or the lumbar spine from genitourinary spread.
Branchial cysts are congenital lesions that can become infected. Infected branchial cysts are a recognised cause of persistent or recurrent neck infections/abscesses.9
A literature search revealed only two case reports of infected branchial cleft cysts becoming complicated by retropharyngeal abscess.10 11
No cases of cervical osteomyelitis or atlanto-axial subluxation resulting from spread of infection from a confirmed branchial cleft cyst were noted, although cervical osteomyelitis is a recognised complication of retropharyngeal infection from other causes, including upper airway infection, dental sepsis and foreign body perforation.12–14
Osteomyelitic destruction of the odontoid peg has been recorded in association with retropharyngeal abscesses15 16
and is associated with neck stiffness and meningism.
Recurrent neck infections should raise the possibility of an underlying congenital lesion such as a branchial cyst. In this case, despite aspiration and surgical excision of the infected branchial cyst, the infection recurred and spread through the retropharyngeal space to involve the upper cervical vertebrae from C1–C5. In association with infection at the C1–C2 level, there was relaxation of the transverse atlantal ligament leading to atlanto-axial instability with neck stiffness and meningism as seen in our case.
- Persistent neck infections may suggest an underlying congenital lesion such as a branchial cyst.
- Retropharyngeal abscesses may become complicated by osteomyelitis.
- Persistent neck pain should always signal the possibility of occult spinal pathology.
- MRI can provide early diagnosis of osteomyelitis.
- Cervical osteomyelitis can become complicated by atlanto-axial instability.