Magnetic resonance myelography in early postoperative lumbar discectomy: An efficient and cost effective modality.

Background: Magnetic resonance myelography (MRM) after lumbar discectomy is all too often an unrewarding challenge. A constellation of findings are inevitable, and determining their significance is often difficult. MRM is a noninvasive technique that can provide anatomical information about the subarachnoid space. Until now, there is no study reported in literature showing any clinico-radiological correlation of post operative MRM. The objective of this study was to prospectively evaluate the diagnostic effectiveness of MRM for the demonstration of decompression in operated discectomy patients and its correlation with subjective and objective outcome (pain and SLR) in immediate postoperative period.

Materials And Methods: Fifty three patients of single level lumbar disc herniation (LDH) justifying the inclusion criteria were operated for discectomy. All patients underwent MRM on second/third postoperative day. The pain relief and straight leg raise sign improvement was correlated with the postoperative MRM images to group the patients into: A- Subjective Pain relief, SLR improved and MRM image showing myelo regression; B- Subjective Pain relief, SLR improved and MRM image showing no myelo regression; C- No Subjective Pain relief, no SLR improved and MRM image showing myelo regression and; D- No Subjective Pain relief, no SLR improved and MRM image showing no myelo regression.

Results: The result showed that Group A had 46 while Group B, C and Group D had 4, 2 and one patients respectively. Clinico-radiological correlation (Clinically diagnosed patient and findings with MRM correlation) was present in 47 patients (88.68%) which includes both A and D groups. The MRM specificity and sensitivity were 92% and 33.33% respectively.

Conclusion: MRM is a non-invasive, efficient and reliable tool in confirming postoperative decompression in lumbar discectomy patients, especially when economic factors are to be considered and the required expertise to reliably read a complex confusing post-operative MRI is not available readily. Further, controlled double blinded multicentric study in operated and non operated LDH, with MRI comparison would give better evidence to justify its use in screening to detect persisting compression and to document decompression.