Magnetic resonance Imaging and magnetic resonance myelography in the presurgical diagnosis of lumbar foraminal stenosis

Study Design. Retrospective case series with a control group. Objective. To measure the diagnostic performance of magnetic resonance imaging (MRI) and MR myelography (MRM) for symptomatic foraminal stenosis in patients who need surgery. Summary of Background Data. MR images are extensively used in the evaluation of foraminal stenosis and are often used to evaluate nerves exiting from the foramen. There has been no published report of the diagnostic performance of these imaging methods (MRI and MRM). Methods. Diagnostic performances were studied in 90 patients in whom the site of the stenosis was confirmed by means of selective decompression surgeries. The disease prevalence among patients was 26% (23 of 90 patients). The disease prevalence among foramens was 3% (25 of 936 foramens). The prevalence of abnormal findings in 27 asymptomatic volunteers was also studied. Two blinded observers interpreted foraminal narrowing on combinations of sagittal and axial MR images, abnormalities of the course of the nerve root in the foramen, and spinal nerve swelling on MRM. Results. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRI for the diagnosis of symptomatic foraminal stenosis were 96%, 67%, 4%, and 100%, respectively. The corresponding values for abnormal nerve root course on MRM were 96%, 83%, 7%, and 100%, respectively, and for spinal nerve swelling on MRM were 60%, 99%, 35%, and 99%, respectively. Conclusions. Compared with conventional MRI, MRM affords more specific information for the presurgical diagnosis of symptomatic foraminal stenosis.