Postoperative outcome of lumbar spinal canal stenosis after fenestration: correlation with changes in intradural and extradural tube on magnetic resonance imaging.

PURPOSE To evaluate the serial changes in clinical results and the intradural and extradural spaces on magnetic resonance imaging (MRI) after bilateral fenestration in 48 patients with lumbar spinal canal stenosis (LSCS). METHODS A prospective interventional study was performed to study the clinical results, magnetic resonance imaging scans among patients who were followed up for more than 3 years. RESULTS All patients showed improvement in clinical symptoms after operation, but clinical results deteriorated in 9 (19%) patients. Postoperative MRI scans showed that poor dural tube expansion, grouping of the cauda equina, and decrease in the cross-sectional area of the dural tube were factors associated with poor outcomes. The cross-sectional area of the dural tube and images of the cauda equina observed by MRI, before and after fenestration and during follow-up, reflected changes in clinical symptoms involving decompressed segments. CONCLUSION Serial changes in the cross-sectional area of the dural tube and images of the cauda equina observed preoperatively, postoperatively, and on follow-up by MRI may be useful when evaluating patients' condition before and after operation. It is also useful for predicting outcomes.