The commonly used preoperative lumbar MRI grading lags behind modern
patient selection criteria to prognosticate favorable outcomes with the endoscopic
decompression for lumbar herniated disc and foraminal and lateral recess stenosis.
Since its utilization has evolved into a primary medical necessity criterion for surgical
intervention, surgeons often find themselves with clinical symptoms whose treatment is
not supported by the MRI report. Therefore, this chapter's authors established the need
to determine the MRI's accuracy and positive predictive value for successful
postoperative pain relief after endoscopic transforaminal decompression. Using the
transforaminal endoscopic technique, the authors performed a critical retrospective
analysis of 1839 patients who had surgery for herniated disc and stenosis in the
foramina or lateral spinal canal. They calculated the sensitivity, specificity, accuracy,
and positive predictive value of preoperative MRI grading, correctly identifying the symptomatic surgical level by correlating it with the directly visualized pathology
during surgery and clinical improvements. The lumbar MRI verbal report's sensitivity
was calculated at 68.34%, the specificity at 68.29%, the accuracy at 68.24%, and the
positive predictive value at 97.38%. The use of surgical MRI criteria for nerve
compression detailed within this manuscript improved the calculated sensitivity to
87.2%, specificity to 73.03%, and accuracy to 86.51%. The likely explanation lies in
the lack of consensus between radiologists and spine surgeons when grading
compression syndromes of the exiting and traversing nerve root. The grading of a
preoperative MRI scan for lumbar foraminal and lateral recess stenosis may
significantly differ between radiologists and surgeons. The authors conclude that the
endoscopic spine surgeon should read and grade the lumbar MRI scan independently.
Keywords: Lumbar endoscopic transforaminal decompression, Preoperative MRI scan.