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

This report illustrates two rare cases of foramen magnum syndrome caused by a retro-odontoid mass in which calcium pyrophosphate dihydrate crystals were found. 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. Deposition of calcium pyrophosphate dihydrate crystals occurs into the fibrous and hyaline cartilage of the joints and intervertebral discs of the spine. Half of the patients known to have a chondrocalcinosis had asymptomatic calcification in the odontoid region. Ten patients were published in the literature as having a spinal cord syndrome secondary to calcium pyrophosphate dihydrate deposition in the odontoid region. In both cases the preoperative studies were analyzed, and the retro-odontoid mass was resected and histologically examined. Both had an anterior transoral approach and have been followed for 1 year. According to the preoperative radiographs the diagnosis was suspected and confirmed histologically. Transoral approach was done with no need in either case for a posterior stabilization. Compression of the spinal cord by calcium pyrophosphate dihydrate deposition may occur. The preoperative diagnosis may be highly suspected after radiographic study and histologically confirmed. Transoral resection is the treatment of choice. Posterior stabilization should be considered only in cases of craniovertebral instability.