Grisel syndrome

• Abnormal lateral subluxation of C1 on C2 with widening of the atlantodental interval on CT
• Prevertebral soft tissue thickening or retropharyngeal infection on imaging
• History of recent head/neck infection or ENT procedure with new onset torticollis in a young child

• Plain radiograph lateral view demonstrates prevertebral soft tissue thickening due to retropharyngeal infection and widening of the atlantodental interval.
• CT is the most common modality and shows abnormal lateral subluxation of C1 on C2, with subluxation of the occipital condyles on C1 in the affected segment.
• Rotational facet displacement alone is not sufficient evidence for true subluxation and can be seen as a normal finding in asymptomatic patients, necessitating careful interpretation in young children.
• Static CT has significant risk of overestimating subluxation due to developmental changes, ligamentous laxity, and positional pseudo-subluxation effects, particularly in pediatric patients with normally lax ligaments.
• MRI is useful for evaluating inflammatory changes in surrounding soft tissues, including disruption of the alar and transverse ligaments that support the atlantoaxial joint.
• MRI also provides excellent assessment for spinal cord compression and myelopathic changes related to the subluxation.
• The interval between the inciting inflammatory event and imaging findings is variable, making early diagnosis challenging when clinical suspicion is high.

• Down syndrome and other connective tissue disorders causing abnormal ligament laxity—distinguished by genetic/syndromic features and typical facial features rather than acute inflammatory trigger.
• Cervical spine instability from other causes—history of recent ENT infection or procedure helps confirm Grisel syndrome as cause of acute subluxation.
• Osteogenesis imperfecta—check for bone quality, history of easy fractures, and characteristic skeletal features.
• Neurofibromatosis type 1—look for neurofibromas, osseous dysplasia, and lack of acute infection trigger.
• Undetected trauma—careful history to rule out recent head/neck injury as alternative cause of atlantoaxial subluxation.
• Normal developmental atlantoaxial laxity in asymptomatic children—clinical presentation of acute torticollis and infection helps distinguish Grisel syndrome from normal variants.

When reporting Grisel syndrome, clearly distinguish between true atlantoaxial subluxation (lateral offset of C1 on C2 with widening of the atlantodental interval) and rotational facet displacement alone, as the latter can be a normal variant in young patients; correlate imaging findings with clinical presentation of acute torticollis and recent infection history to avoid overdiagnosis of asymptomatic positional changes.

• Overestimating subluxation on static CT due to positional pseudo-subluxation and normal developmental ligamentous laxity in young children, leading to unnecessary intervention.
• Mistaking rotational facet displacement for true subluxation; rotational changes alone are not sufficient evidence for clinically significant subluxation.
• Failing to consider Grisel syndrome in the differential diagnosis of acute torticollis in a child with recent ENT infection or procedure, delaying diagnosis and treatment.
• Over-relying on CT imaging without clinical correlation; delayed diagnosis occurs when the time interval between infection and imaging is variable and laboratory findings are normal.