Atlantoaxial subluxation in an adult secondary to retropharyngeal abscess.

Atlantoaxial subluxation secondary to a retropharyngeal abscess is well described in children, but very rare in adults. Only two adult cases have been reported in the literature. We present a case of severe atlantoaxial subluxation in an adult secondary to retropharyngeal abscess. His atlas-dens interval was very large, up to 10 mm in flexion. We tried external fixation with a neck collar initially, but for remaining instability, surgical fusion was performed. The mechanism of subluxation is attributed to softening of the ligament allowing greater mobility at the joint. The etiology of this process is speculative.