ASSESSMENT OF THE NARROW CERVICAL SPINAL-CANAL - A PROSPECTIVE COMPARISON OF MRI, MYELOGRAPHY AND CT-MYELOGRAPHY

This study was designed to compare the accuracy of magnetic resonance imaging (MRI), myelography and computed tomography in the assessment o f degenerative cervical spinal stenosis. We prospectively examined a t otal of 75 spinal segments in 18 patients with suspected cervical spin al canal stenosis, using sagittal spin-echo and axial gradient-echo se quences generated by a 1.5 Tesla imager, conventional myelography, and computed tomography with intrathecal contrast medium (CT-myelography) . The degree of stenosis was often overestimated using MRI. This error was most prominent in cases of severe stenosis but was significant wi th minor to moderate stenosis. In these cases, the clinical consequenc es of such an overestimation can be serious, because treatment is misd irected. The error is probably caused by pulsation of the cerebrospina l fluid and truncation artefact (Gibbs phenomenon). MRI at 1.5 Tesla i s thus frequently inadequate for diagnostic assessment of degenerative cervical spinal stenosis. Myelography and myelographic CT are still u seful for decisions on operative treatment, especially in cases of mod erate stenosis. This may, however, not apply to imagers operating at 0 .5 Tesla as below.