Foramen magnum syndrome secondary to calcium pyrophosphate crystal deposition in the transverse ligament of the atlas

Study Design. This report illustrates two rare cases of foramen magnum synd rome caused by a retro-odontoid mass in which calcium pyrophosphate dihydra te crystals were found, Objectives, To analyze the preoperative studies and the diagnostic criteria and to discuss the surgical treatment. The present cases will be compared with previous ones described in the literature. Summary of Background Data. Deposition of calcium pyrophosphate dihydrate c rystals occurs into the fibrous and hyaline cartilage of the joints and int ervertebral discs of the spine. Half of the patients known to have a chondr ocalcinosis had asymptomatic calcification in the odontoid region. Ten pati ents were published in the literature as having a spinal cord syndrome seco ndary to calcium pyrophosphate dihydrate deposition in the odontoid region. Methods, In both cases the preoperative studies were analyzed, and the retr o-odontoid mass was resected and histologically examined, Both had an anter ior transoral approach and have been followed for 1 year. Results. Accordin g to the preoperative radiographs the diagnosis was suspected and confirmed histologically. Transoral approach was done with no need in either case fo r a posterior stabilization. Conclusions, Compression of the spinal cord by calcium pyrophosphate dihydr ate deposition may occur. The preoperative diagnosis may be highly suspecte d after radiographic study and histologically confirmed. Transoral resectio n is the treatment of choice. Posterior stabilization should be considered only in cases of craniovertebral instability.