Imaging description

Most disc herniations are hypointense on T2-weighted images, similar to the degenerated intervertebral disc they are associated with, which allows easy recognition and characterization of disc herniations on T2-weighted images thanks to increased contrast between the hypointense disc material and the hyperintense CSF and epidural fat. A small group of disc herniations are hyperintense on T2-weighted images with a diminished contrast between the disc material and CSF/epidural fat, leading to diagnostic errors (Fig. 93.1). In particular, relatively large T2 hyperintense fragments within the lateral recesses or foramina of the lumbar spine can go undetected because the thecal sac shows no significant contour deformity (Fig. 93.2). Yet disc herniations in the lateral recesses and foramina may potentially be more symptomatic, with more obvious radiculopathy due to compression of the descending or exiting nerve roots. In the cervical spine, T2 hyperintense disc herniations extending to the neural foramina can be missed because of high T2 signal of the epidural venous plexus, particularly on the gradient echo sequences. Foraminal disc herniations usually present with clear radiculopathy (Fig. 93.3). There is no clear understanding of why some disc herniations have increased T2 signal. There have been studies of acute traumatic disc herniations showing elevated T2 signal associated with disc herniations [1,2], but no systematic assessment of non-traumatic disc herniations with regards to T2 hyperintensity has been reported other than some anecdotes [3,4]. If contrast is given, T2 bright disc herniations usually show a rim enhancement.