A Case of Grisel Syndrome Showing No Underlying Laxity of the Atlanto-axial Joint.

Grisel syndrome is a rare, non-traumatic atlanto-axial subluxation associated with an inflammatory or infectious process in the upper neck. According to the two-hit hypothesis, which is widely accepted for the pathogenesis of Grisel syndrome, preexisting ligamentous laxity of the atlanto-axial joint is regarded as the first hit. An inflammatory or infectious process of the atlanto-axial joint acts as the second hit, resulting in non-traumatic atlanto-axial subluxation. We report on a 6-year-old girl with atlanto-axial subluxation following retropharyngeal and cervical lymphadenitis. She was diagnosed with Grisel syndrome, for which an initial computed tomography did not show any preexisting ligamentous laxity of the atlanto-axial joint. A literature review found only 4 case reports on Grisel syndrome with an initially normal atlanto-axial joint. The present case offers some evidence that a single hit, such as inflammatory changes in the atlanto-axial joint, might cause Grisel syndrome, even without underlying ligamentous laxity.