Early postoperative gadolinium-DTPA-enhanced MR imaging after successful lumbar discectomy.

A prospective study was undertaken to establish the normal spectrum of early gadolinium-enhanced magnetic resonance (MR) imaging findings in patients who had resolution of symptoms after lumbar discectomy. Thirty-four patients underwent MR examinations 6 weeks and 6 months after lumbar discectomy on a 1.5 T superconducting unit, including sagittal and axial spin-echo (SE) T1-weighted images before and after intravenous administration of gadolinium-DTPA, as well as sagittal turbo (or fast-) SE T2-weighted images. All patients showed soft tissue enhancement along the surgical track in the subcutaneous soft tissue lateral to the spinous process and in the epidural space. There was only minimal (45%) or no (55%) mass effect on the dural sac associated with epidural scar formation 6 months after surgery, but often the nerve root at the operative level was surrounded by this enhancing tissue. Facet joint enhancement was seen in most patients 6 weeks (63%) and 6 months (53%) after surgery. Intrathecal nerve root enhancement was observed in six patients, 6 weeks after surgery. Nine patients (20%) had residual mass effect on the neural elements with an enhancement pattern suggestive of a disc fragment. Enhancement of the intervertebral space was seen in 67% of patients 6 weeks after surgery and in 86% of patients after 6 months. It may be concluded that, despite the use of gadolinium-DTPA, MR studies obtained in the initial postoperative period are difficult to interpret, because of the normal sequence of changes. Consequently, the clinical picture still remains the major indicator for recurrent surgery.