PERIODONTOID PSEUDOTUMOUR IN FORESTIER’S DISEASE
Luís B. Cardoso
Introduction: Diffuse idiopathic skeletal hyperostosis (DISH), or Forestier’s disease, is a common but underdiagnosed skeletal condition in which the anterolateral aspect of a set of continuous vertebral bodies undergoes ossification in the absence of significant disc degeneration, apophyseal joint ankylosis, or sacroiliac joint fusion. Compression of the trachea and esophagus are the most common symptoms induced by the ossification of the anterior longitudinal ligament. As in other nosological entities, some patients develop a soft tissue mass by the level of C1-C2 that resembles a tumour.
Case Presentation: We present the cases of three elderly patients who performed MR and CT imaging in the context of intense cervical pain; one patient also had progressive solid dysphagia and dysphonia, and none had neurological deficits. The exams showed ossification of the anterior longitudinal ligament and pronounced anterior osteophytes of the cervical spine with anterior dislocation of the prevertebral soft tissues. There was a large, smooth, mass behind the odontoid process with heterogeneous but mainly low signal on T1 and T2 sequences, and foci of erosion of the odontoid process in two of the patients. The high cervical cord was posteriorly deviated by the retro-odontoid mass, but with no signs of myelopathy on T2-STIR.
Conclusion: DISH is a systemic noninflammatory disease and a well-recognized entity, characterized by ossification of the entheses. The disease tends to affect the middle to lower cervical region more than the upper cervical region. The lost of mobility below C2, secondary to contiguous ossification, with cervical motion concentrated at the atlantooccipital and atlantoaxial joints, leads to greater strain of the mobile occipitoatlantoaxial segment inducing partial tears of the ligaments. Pseudotumor formation is thought to result from the soft tissue hypertrophy as reaction to this mechanical stress.