• Clemens Weber, Kjell Arne Kvistad, Viggo A Moholdt, Øystein P Nygaard, and Ole Solheim.
• *Department of Neurosurgery, Stavanger University Hospital, Stavanger, Norway†National Advisory Unit on Spinal Surgery, St. Olavs University Hospital, Trondheim, Norway‡Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway§Department of Radiology, St. Olavs University Hospital, Trondheim, Norway¶Department of Neurosurgery, St. Olavs University Hospital, Trondheim, Norway||Norwegian Advisory Unit for Ultrasound and Image-Guided Surgery, St. Olavs University Hospital, Trondheim, Norway.
• Spine. 2016 Feb 1; 41 (3): 239-45.

Study DesignProspective cohort study.ObjectiveTo describe the naturally occurring magnetic resonance imaging (MRI) findings after successful microsurgical removal of lumbar disc herniation with repeated MRI examinations.Summary Of Background DataThe interpretation of MRI after spinal surgery may be particularly challenging and image findings do not always correlate to clinical findings. Early postoperative MRI has limited value in the evaluation of patients after surgery for lumbar disc herniation.MethodsProspective study of 30 successfully operated patients, which underwent 3.0 T MRI within 24 h after surgery for lumbar disc herniation and repeated at 6 weeks and 3 months postoperatively. Postoperative image findings (nerve root enhancement, nerve root thickening, displacement or compression of the nerve root, and residual mass size and signal) were assessed quantitatively. Inter-rater reliability was tested.ResultsInter-rater reliability between neuroradiologists was moderate for assessed MRI variables. In the immediate postoperative phase, compression or dislocation of the nerve root at the operated level was common. A residual mass at the operated level was seen in 80%, 47%, and 33% after 24 h, 6 weeks, and 3 months, respectively. Postoperative dislocation or compression of the nerve root from residual masses was seen in 67%, 24%, and 14% after 24 h, 6 weeks, and 3 months, respectively. A residual mass with a higher signal than muscle on T2-weighted images was seen in 80%, 30%, and 17% after 24 h, 6 weeks, and 3 months, respectively.ConclusionA residual mass with compression or dislocation of the nerve root at the operated level, that disappears over 3 months, is a common MRI finding in patients successfully operated for symptomatic lumbar disc herniation. An expectant approach instead of early reoperations may perhaps be preferred in patients with residual pain and root compression due to residual masses with high T2-signal since these often seem to resolve spontaneously.Level Of Evidence3.

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