Hypertrophic dens resulting in cervical myelopathy - Histologic features of the hypertrophic dens

Study Design. A case report of a 43-year-old woman who had hypertrophic den s in the developmentally narrow atlas ring that resulted in cervical myelop athy. Objectives. To present histologic findings of the hypertrophic dens, which was excised en bloc by the transoral approach, and to discuss the pathogene sis of the hypertrophic change of the dens. Summary of Background Data. Few cases have been reported of cervical myelop athy associated with hypertrophic dens, and there have been no previous rep orts describing the histologic features of hypertrophic dens. Methods, Clinical data were reviewed from the patient's chart, and histolog ic features of the hypertrophic dens were examined in the sagittally cut se ction. Results. After posterior decompression surgery, cervical myelopathy in the patient subsided. Myelopathy reappeared 4 years after surgery. Imaging stud ies showed osteoarthritis of the atlantodental joint, hypertrophic dens, an d degeneration of the cruciate ligament. In the second surgery, transoral r emoval of the dens with posterior occipitocervical fusion was performed. Hi stologic studies showed thickening of the cortical bone of the anterior and cranial parts of the dens. The apical portion, which was the insertion por tion of the ala ligaments, showed degenerative changes of tide marks. Conclusion. Atlantoaxial instability and enthesopathy were probably the cau ses of the hypertrophic changes of the dens in this case.