Case report of a retropharyngeal synovial cyst originate from atlantoaxial joint and review of the literature

Synovial cysts of the atlantoaxial joint are rare entities [1] and could possibly grow in any direction and compress adjacent structure. Synovial cysts of the atlantoaxial joint have been associated with atlantoaxial instability because of trauma or chronic inflammation. They could grow in the retropharyngeal space, lateral to the spine or towards the spinal canal either epidural or intradural and cause progressive myelopathy [2]. Rarely synovial cysts could cause acute clinical symptoms because of hemorrhage [5]. In this article, we present a case report of a 72 years old man presented with subtle upper neck pain and after cervical MRI (Magnetic Resonance Imaging) has been diagnosed with a retropharyngeal cystic mass originating from atlantoaxial arthrosis. Patient treated conservatively with analgetic medication. Neck pain went off without remission and there was no relapse during the last 5 years of follow up. Repeated cervical MRI revealed no change of the cyst size and morphology and patient remained asymptomatic. Atlantoaxial instability was not present in flexion extension x-rays. Laboratory results for rheumatoid arthritis were negative.