Background and importance: Acquired atlantoaxial instability of inflammatory origin (Grisel syndrome) is a rare condition. It usually occurs in children with benign upper airway problems and responds well to immobilization, rarely requiring C1-2 arthrodesis. Our recent experience with 2 adult cases suggests this may not be true in an older subpopulation.
Clinical presentation: A 71-year-old man developed C1-2 instability in the setting of culture-negative endocarditis. Initial immobilization was attempted for 8 weeks but new imaging revealed progressive destruction of the odontoid and worsening instability. Symptoms resolved after C1-4 arthrodesis. A 35-year-old woman developed C1-2 instability after a molar extraction and otitis media. Despite 12 weeks of immobilization and antibiotics, symptoms persisted and the atlantodental interval increased. She was successfully treated with a C1-2 arthrodesis.
Conclusion: A literature review revealed 13 reports (14 cases) of inflammatory atlantoaxial instability in patients aged 18 and older since 1830. Including the 2 cases reported here, 11 cases underwent initial nonoperative treatment with durable satisfactory results in only 2 of them (18.2%). Aspiration of the C1-2 phlegmon was diagnostic in only 4 of these 16 cases. Destruction of the odontoid was seen in a minority of cases (5/16, 31.3%). In this first review of the topic since the introduction of screw-based C1-2 fixation, it is suggested that nonoperative treatment is futile for inflammatory atlantoaxial instability in adults and strong consideration should be given to C1-2 arthrodesis. This procedure can reliably produce good outcomes with minimal morbidity.