ABSTRACT

Aim:

The degenerative lumbar spinal stenosis (LSS) is a dynamic phenomenon. Changes in posture and physical activities as standing and walking can aggravate symptoms. The aim of the study was to evaluate the results of post axial loading Computed Tomography Myelography (CTM) versus Magnetic Resonance Imaging (MRI) in patients undergoing surgery for multilevel degenerative lumbar spinal stenosis.

Methods:

Thirty patients with multilevel degenerative LSS scheduled for elective surgery were enrolled in the study. Preoperatively, all patients underwent both MRI and CTM, in supine psoas relaxed position and post loading by axial compression in slight extension. Quantitative evaluation for LSS was conducted by two experienced radiologists. The parameters included dural sac cross sectional area, lateral recess and foraminal evaluations for stenosis, on CTM and MRI. Statistical analysis of the data was performed to evaluate relative advantages and additional information depicted by axial loaded CTM versus MRI.

Results:

In 21 of 30 of patients, axially loaded images demonstrated additional information, such as findings of spinal canal encroachment, deformation of the dural sac and nerve roots, reduction in cross sectional dural sac area, narrowing of the lateral recess, increased number and severity of affected stenotic sites particularly in borderline cases after axial compression. In 11 patients, borderlines for stenosis were passed in at least one level. CTM and MRI findings were comparable.

Conclusion:

Axial loading mimics erect posture on CTM and MRI, thus partially eliminating the diagnostic dilemma associated with the dynamic nature of LSS. The study demonstrated underestimation of extent and severity of LSS on preloading images. Post axial loaded CTM and MRI added valuable information to the preoperative assessment of patients of multilevel spinal stenosis by identifying additional levels and severity of stenosis, particularly in borderline cases.