SERIAL MRI IN THE EARLY POSTOPERATIVE PERIOD AFTER LUMBAR DISKECTOMY

The aim of this study was to determine MRI findings in patients succes sfully operated upon for lumbar disc herniation. We investigated 20 pa tients with a successful outcome after L4-5 or L5-S1 disc operations c linically and with MRI preoperatively, and at 5 days, 6 weeks, and 4 m onths after surgery. Postoperatively, T1- and T2-weighted images were obtained. At 4 months gadolinium-enhanced images were added. Pronounce d intraspinal MRI changes were seen during follow-up. Deformation of t he dural sac was seen in 13 patients preoperatively, in 19 at 5 days a fter operation, in 15 at 6 weeks, and in 12 at 4 months. Nerve root in volvement was seen in all cases both preoperatively and at 5 days afte r operation, in 17 at 6 weeks, and in 15 at 4 months. No correlation b etween symptoms or the straight leg raising test and the size or natur e of the abnormal tissue in the spinal canal postoperatively could be demonstrated. It was concluded that early postoperative MRI after lumb ar discectomy must be interpreted carefully, and that oedema and scar formation are probable reasons for difficulties in interpretation.