Tonsillar herniation and the cervical spine: a morphometric study of 172 patients.

BACKGROUND

When the neck is flexed in patients with Chiari I malformation, herniated tonsils descend, impacting the spinal canal, and the clivus-canal angle changes and compresses the ventral spinal cord. Therefore, we speculated that the existence of tonsillar herniation might have some influence on the cervical spine, such as changes in range of motion, sagittal alignment, and spondylosis. The purpose of this radiological study was to clarify quantitatively the relation between tonsillar herniation and the cervical spine regarding range of motion, sagittal alignment, and cervical spondylotic change.

METHODS

We examined the cervical spine of 609 outpatients with magnetic resonance imaging, and the cerebral tonsils being located below the foramen magnum was defined as tonsillar herniation. Of the 609 patients, 88 (14.4%) had tonsillar herniation. Two of the 88 patients who had complicating osseous anomalies were excluded from this study, and the remaining 86 patients with tonsillar herniation were the subject group (TH group). Of the remaining 521 patients without tonsillar herniation, 86 patients whose age and sex matched those of the TH group were selected at random to be in the control group (Non-TH group). The range of motion, sagittal alignment, and the diameter of the intersegmental dura in the cervical spine in the TH group were compared by age with those in the Non-TH group using a roentgenograph or magnetic resonance imaging.

RESULTS

The range of motion at C1-C2 was significantly smaller in the TH group (5.4 degrees ) than in the Non-TH group (8.4 degrees ) in patients over 70 years of age. The level of narrowing of the dura diameter at C5/C6 was significantly higher (P = 0.029) in the TH group (23.3%) than in the Non-TH group (13.4%) in patients over 70 years of age. The cervical alignment was similar in both groups for all age groups.

CONCLUSIONS

The existence of tonsillar herniation was associated with loss of range of motion at the upper cervical spine and progression of spondylotic change, especially in elderly patients.