Clinical value of extension-flexion MRI in evaluating the indication of internal fixation for patients of craniovertebral junction malformation

Abstract

Objective To analyse the value of cervical extension-flexion magnetic resonance imaging (EFMRI) in the evaluation of possible atlantoaxial dislocation (AAD) associated with Arnold-Chiari malformation. Methods Reviewed the image studies of 40 Arnold-Chiari malformation patients, including 19 females and 21 males. The cervical EFMRI was evaluated, atlantodental interval (ADI) was measured and spinal canal narrowing grade was evaluated to judge the instability of craniovertebral junction (CVJ). The diagnostic criteria of instability of CVJ was that ADI increased more than 2 mm between flexion and the neutral or extention position in dynamic MRI, or the spinal canal stenosis grade increased more than one grade between flexion and the neutral or extention position in dynamic MRI. Foramen magnum decompression and cisterna magna plasty were performed for the Arnold-Chiari malformation patients without instability of CVJ. For patients who were diagnosed instability of CVJ, occipitocervical internal fixation and fusion was indicated besides decompression. Results Twelve patients were diagnosed as instability of CVJ, and occipitocervical internal fixation and fusion, foramen magnum decompression and cisterna magna plasty were performed. In the 40 patients, the syringomyelia of 10 patients shrinked on the MRI on the third day postoperatively. There was no movement of the instruments in 12 patients with internal fixation, and the spinal cord was well decompressed. Three months after surgery, the syringomyelia of 17 patients obviously shrinked in MRI. The bony bridge was demonstrated in CT in 12 cases. Japanese Orthopedic Association (JOA) score at 3 months after surgery was 13.08 ± 1.40, and was higher than that of preoperation significantly (t = 5.928, P = 0.000). Conclusion Cervical EFMRI has significant value in the evaluation of possible AAD in patients of Arnold-Chiari malformation, and can help to determine the surgical strategy. DOI:10.3969/j.issn.1672-6731.2011.04.015