Hypertrophic dens resulting in cervical myelopathy: histologic features of the hypertrophic dens

A case report of a 43-year-old woman who had hypertrophic dens in the developmentally narrow atlas ring that resulted in cervical myelopathy.

To present histologic findings of the hypertrophic dens, which was excised en block the transoral approach, and to discuss the pathogenesis of the hypertrophic change of the dens.

Few cases have been reported of cervical myelopathy associated with hypertrophic dens, and there have been no previous reports describing the histologic features of hypertrophic dens.

Clinical data were reviewed from the patient's chart, and histologic features of the hypertrophic dens were examined in the sagittally cut section.

After posterior decompression surgery, cervical myelopathy in the patient subsided. Myelopathy reappeared 4 years after surgery. Imaging studies showed osteoarthritis of the atlantodental joint, hypertrophic dens, and degeneration of the cruciate ligament. In the second surgery, transoral removal of the dens with posterior occipitocervical fusion was performed. Histologic studies showed thickening of the cortical bone of the anterior and cranial parts of the dens. The apical portion, which was the insertion portion of the ala ligaments, showed degenerative changes of tide marks.

Atlantoaxial instability and enthesopathy were probably the causes of the hypertrophic changes of the dens in this case.