A 10-years old girl with 3 months history of neck pain and stiffness experienced sudden worsening of symptoms with severe neck pain, headache, nausea with vomiting and dizziness. A clinical examination revealed torticollis with limited head rotation to the left, multiple reactive lymph nodes and subfebrile (37,5°C) body temperature.
US findings included multiple bilateral reactive lymph nodes and contracted sternocleidomastoid muscle (fig. 1).
Radiographs (fig. 2a, 2b) revealed signs of upper cervical vertebra rotation with no visible atlantoaxial subluxation (AAS).
On MR imaging C1 to C2 subluxation of 70° was observed, with preserved transverse ligaments (fig. 3). Atlantodental interval (ADI) was 4,8 mm, basilar invagination with preserved tectorial membrane was present (fig. 4). There were no signs of bone fracture or compressive myelopathy. Small effusion in atlantoaxial joint was present.
CT scan revealed 50° rotation of the C1 to the left and minor C2 to C3 rotation to the right without luxation or subluxation of facet joints (fig. 5). Basilar invagination of the dens was measured to 6 mm and posterior atlantodental interval (PADI) was measured to 13 mm (fig. 6).
AAS is characterized by a loss of stability between the C1 and C2 caused by either traumatic or nontraumatic causes . Nontraumatic AAS combines many different entities, including nasopharyngeal torticollis (Grisel syndrome), atlantoaxial rotator subluxation (AARS), atlantoaxial rotator fixation (AARF), atlantoaxial rotator dislocation, spontaneous hyperemic dislocation and distension luxation .
Grisel syndrome usually affects children aged 8-12 years  as a result of conditions such as adenotonsilitis, pharyngitis, tonsillar abscess, cervical abscess and otitis media which lead to hyperemia and pathologic relaxation of the transverse ligament of the atlantoaxial joint causing AAS . Its typical presentation with torticollis, cervical pain and signs of infection was evident in our case .
Most cases of AAS can be identified on plain radiography but CT scan provides additional information regarding the identification and characterization of AAS [1, 2]. The ADI is measured from the anterior surface of the dens to the posterior surface of the anterior arch of C1 ; distance greater than 5 mm in children is indicative of AAS. Another marker is the PADI, measured from the posterior surface of the dens to the anterior surface of the posterior arch of C1 and should normally measure more than 13 mm. The PADI value has 97% sensitivity for predicting neurologic deficit . Diagnostic criteria for basilar invagination is projection of dens for at least 5 mm above the McGregor's line . The ADI and the PADI measures were borderline in our case, however basilar invagination and C1-C2 rotation were observed.
MRI can be used to obtain additional information on cervical spine and soft tissue changes in patients with questionable neurologic status in first 48h after injury and additional information on ligament disruption and its clinical relevance in patients with CT signs of instability .
Treatment consists of conservative and surgical options. Conservative methods with cervical collar, halo fixation and halter traction were primarily used in our case . Since they did not provide an accurate position, surgical treatment with craniocervical fusion was required. Surgical treatment is usually indicated in children when one or more of the following is present: neurologic deficit, persistent anterior displacement with ADI more than 4 mm, deformity lasting for more than 3 months, or its recurrence after 6 weeks of immobilization .
6 months after the surgery symptoms resolved with only a minor decrease in range of motion (fig. 7).
Teaching points: Nontraumatic AAS should be considered in case of a child with persisting torticollis and signs of infection .
Written informed patient consent for publication has been obtained.
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