Objectives: To evaluate and compare the imaging of lumbar spinal canal stenosis using plain radiographs, CT-Myelogram and MRI.

Patients and Methods: Prospective study at Medical College Calicut during 2002-2004. 25 patients of age from 25 to 69 years, with clinical features of lumbar spinal canal stenosis were evaluated. Inter pedicular distance, anteroposterior diameter and thecal sac cross sectional area (IPD, APD and TSCA) were measured using plain radiographs, CT-Myelogram and MRI, in all 25 patients.

Results: Soft tissue compression evaluated as disc protrusion and ligamentum flavum hypertrophy detected in 20 patients by CT-myelography and 22 patients by MRI. Thecal sac cross sectional area at stenosed level were assessed and compared with CT- Myelography and MRI, out of 25 patients 10 and 11 patients were detected with significant narrowing by CT-Myelogra-phy and MRI respectively in which 2 cases of severe thecal sac compromise (< 76 mm2) detected by CT-Myelography and 3 cases by MRI. CT–Myelography detected one case of single level absolute stenosis (AP diameter of < 10mm), but none of the cases were detected by MRI or Plain radiography. Relative stenosis (AP diameter of 10-12mm) at single level detected in 6 cases by CT–Myelography, in 4 cases by MRI and in 3 cases by plain radiography. Relative stenosis at multiple level detected in 3 cases by CT–Myelogra-phy, in 4 cases by MRI and in 6 cases by plain radi-ography.4 cases of multilevel absolute stenosis were detected by all 3 modalities.

Conclusions: CT- Myelographic measurement are well correlating with clinical symptoms and MRI findings. Bony Canal measurements obtained by CT- myelogra-phy are superior to same measurements obtained by MRI. Thecal-sac cross sectional area measurements obtained by CT-Myelography is comparable with that of MRI, even though soft tissue involvement in lumbar spinal canal stenosis is more clearly detected by MRI. In comparison of AP diameter taken by plain radiograph and CT- Myelography, X-ray measurements shows only 50-60% accuracy. AP diameter in CT- Myelography and MRI were comparable, when the thecal-sac cross sectional area measured by MRI taken as gold standard (using Karl pearsons correlation coefficients). CT-Myelography shows sensitivity of 92% and specificity of more than 96%.