Comparison of MRI and Myelography / CT Myelography to Determine the Exact Level of Decompression in Patients Suffering from Degenerative Lumbar Canal Stenosis

Introduction & Degenerative lumbar spinal canal stenosis is one of the common entities in neurosurgery. Myelography and CT myelography as one of the first diagnostic procedures still retains its place in some cases. MRI defects in understanding some dynamic aspects of this pathology have been exposed. In order to compare the diagnostic value of these two methods, few studies have focused on lumbar spinal canal stenosis, almost all of them were retrospective. This prospective study designed to compare the diagnostic value of these two methods and to determine the factors affecting reliability of each method.
83 patients underwent preoperative MRI and myelography-CT myelography. Pictures were anonymously assessed by two neurosurgeons and the number of levels required laminectomy was recorded according to each modality. Another neurosurgeon intraoperatively assessed the number of levels in need of laminectomy. Inter-observer reliability for each modality and coordination of preoperative findings with intraoperative findings were calculated using kappa coefficient. The impact of demographic, medical history, physical examination and radiologic findings on the superiority of either of the two modalities were analyzed using T test, Chi square and Spearman correlation coefficient. Analysis was performed with SPSS software and (P Kappa coefficient between two evaluators was 0.61 for MRI and 0.56 for Myelography-CT myelography. This coefficient for agreement of MRI findings with intraoperative findings in 2 evaluations was 0.52 and 0.5 whereas Myelography-CT myelography revealed 0.43 and 0.45 agreement in two evaluations. After excluding the patients with disc herniation, Kappa for myelography/CT myelography has declined considerably to 0.36 and 0.39 in two evaluations. In evaluating the impact of various factors on the diagnostic value of each of these modalities, only lateral recess stenosis was almost related to higher diagnostic value of myelography/CT myelography (P = 0.056).
MRI with regard to higher agreement with intraoperative findings and higher Inter-observer reliability should be the diagnostic test of choice to decide on the extent of laminectomy. Myelography/CT myelography can be used for patients with lateral recess stenosis, patients with a history of previous lumbar spine surgery and Instrumentation or as an alternative to MRI with almost the same diagnostic accuracy in patients with disc herniation.