INTRODUCTION: A retroodontoid pseudotumor, non‐neoplastic mass arising posterior to the odontoid process of the axis, is known to be a cause of cervical myelopathy. However, therapeutic strategy for a retroodontoid pseudotumor is still controversial. Some reports have demonstrated that only posterior fusion of the occipitocervical fusion results in regression of the pseudotumor, while others have reported that anterior resection of the mass is necessary for decompression of the spinal cord. Our hypotheses are that atlantoaxial posterior fixation and fusion without decompression of the spinal cord results in improvement of neurological function immediately after surgery and regression of retroodontoid pseudotumors. The purpose of this study was to determine the efficacy of posterior fixation and fusion alone for patients with a retoroodontoid pseudotumor.
METHODS: Patients with cervical myelopathy secondary to a retroodontoid non‐neoplastic mass were reviewed. Patients with rheumatoid arthritis (RA) and who had been undergoing hemodialysis were excluded. Eight patients were included in the present study. All patients underwent surgical stabilization procedures including occipitocervical (O‐C2) fixation or atlantoaxial (C1‐2) fixation at our institute between 1988 and 2001. There were five male and three female. Ages at the operation were from 47 to 76 years old (mean 63.4 years). The follow‐up periods after surgery were 4 years to 6 years (mean 7.5 years). Neurological and radiological examinations for all patients were reviewed preoperatively and at follow‐up. After the surgery, relationships among the regression of retroodontoid masses, neurological recovery and fused levels (O‐C2 or C1‐2) were examined over time utilizing Magnetic resonance imaging (MRI).
RESULTS: Dynamic cervical lateral X rays and MRI revealed atlantoaxial instability and an anterior epidural mass at the level of the odontoid process in all eight patients, respectively. The retroodontoid mass showed iso signal intensity with spinal cord on T1 weighted images and low signal intensity on T2 weighted images. Seven patients underwent O‐C2 fixation and one patients had C1‐2 fixation. One patient has died for GVHD postoperatively. At follow‐up, eight patients had neurological recovery and solid fusion. The pseudotumors were spontaneously reduced after not only O‐C2 fixation, but also C1‐2 fixation. The regression was followed by improvement of neurological function after surgery. Autopsy was done in the patient died for GVHD. Histological examination of the retroodontoid mass revealed a fibrocartilaginous material, but not inflammatory or tumor cells.
CONCLUSIONS: We demonstrated that posterior fixation and fusion of O‐C2 or C1‐2 resulted in regression of the retroodontoid pseudotumor and improvement of neurological function. These results suggest that a pathomechanism of the retroodontoid pseudotumor is associated with atlantoaxial instability and that C1‐2 posterior fusion only can achieve good clinical and radiological outcomes, as well as O‐C2. Although it may not be possible to lead strict conclusion about surgical procedures since the number of patients is too small, we recommend C1‐2 posterior fixation without decompression for patients with cervical myelopathy secondary to a retroodontoid pseudotumor.
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