Imaging description

MRI is the modality of choice for evaluation of the post-discectomy spine if there is a suspicion for recurrent disc herniation. Intravenous gadolinium should be routinely administered, as it helps in the differentiation of recurrent disc herniation from postoperative scarring. Moreover, it may assist with diagnosis of postoperative arachnoiditis and spinal infection. Sagittal as well as axial images should be routinely obtained in postoperative spine without and with intravenous gadolinium (Figs. 95.1, 95.2, 95.3)

Differentiation between recurrent disc herniation and scar is crucial in the management, but it is not an easy task. This is because of accompanying postsurgical alterations and edema, as well as frequent co-incidence of scar and herniated disc. Herniated disc is generally low in T1 signal and T2 signal. One may be able to identify a thin band of very low signal surrounding the disc, suggestive of fibers of annulus. However, the disc material may occasionally be bright on T2-weighted sequences. Recurrent disc herniation generally does not enhance with intravenous contrast other than at its periphery [1]. However, it is imperative that the imaging should begin promptly after contrast administration. The disc may enhance homogeneously on delayed enhanced images and may therefore be inseparable from scar.