Magnetic resonance image findings in the early post-operative period after anterior cervical discectomy

Abstract

If early neurological deterioration occurs following anterior cervical discectomy, the patient should be evaluated by urgent MRI scanning. In order to interpret such a scan it is essential to know what the normal post-operative MRI appearance is following an uncomplicated procedure. In the lumbar spine it is well recognized that early post-operative imaging following discectomy is difficult to interpret with a high rate of false positive scans. The normal appearance of MRI in the early post-operative period was evaluated prospectively in 15 patients undergoing anterior cervical discectomy without fusion for either cervical radiculopathy or myelopathy. MRI was performed on the first post-operative day, at 6 weeks and 6 months. The successful outcome of the procedure was validated by uniform improvement of Visual Analogue Scale measurement for neck and arm pain, the Neck Disability Index and European Myelopathy Score as appropriate. In contrast to the established findings following lumbar discectomy, only two cases showed a persistent epidural mass in the first post-operative scan and this had completely resolved at 6 months. All patients had foraminal narrowing and root or cord compression pre-operatively. Sixty six percent of cases showed persistent foraminal narrowing on sequential imaging up to 6 months despite showing good symptomatic improvement. All cases demonstrated high signal in the operated disc space on T2 weighted imaging on the first post-operative day and this finding persisted in 13 of 15 scans performed at 6 weeks. Post contrast imaging demonstrated no enhancement of operated disc space and adjacent vertebral body on the first post-operative day, whereas all scans at 6 weeks showed enhancement and such enhancement persisted at 6 months in 50%. Persistent epidural filling defects are uncommon following successful anterior cervical discectomy but persistence of foraminal narrowing is common despite successful outcome. Enhancement of the disc space is also common and does not in itself imply infection.