short tau inversion recovery (STIR) and T1-weighted fast spin echo (FSE) sequences, as well as axial, coronal, and sagittal T2­weighted techniques. The STIR sequence is used to detect bone marrow edema patterns, indicating stress reaction or fracture, as well as soft tissue abnormalities such as spinal cord and nerve root edema, annular fissures, facet joint cysts, and fascial/ intramuscular edema. The coronal sequence is helpful to con­firm transitional lumbosacral anatomy, assess coronal balance, and detect extraforaminal disc herniations. At our institution, axial sequences are obtained in multiple overlapped slices without gaps and parallel to the disc space, to best evaluate the degree of central stenosis and disc contour, and in the cervical spine to also assess the degree of neural foraminal stenosis. Pro­tocols in which axial sequences are prescribed only through the disc space, with gaps between disc spaces, may fail to include a disc sequestration or extrusion extending cephalocaudal to the disc space (▶Fig. 3.2). In the cervical spine, the coronal sequence is replaced with a 2D gradient recalled echo sequence to help differentiate between posterior endplate osseous remodeling and ridges, which are low signal intensity, and disc herniations, which are typically of higher signal intensity. Gado­linium T1-weighted sequences have a role both in the pre- and postoperative setting, but for disc pathology they are typically used to differentiate between postoperative epidural fibrosis, which will enhance, and residual or recurrent disc herniation, which will not enhance. imaging parameters of conventional sequences are optimized to reduce susceptibility effects. Dedicated metal artifact reduc­tion sequences developed mainly for arthroplasty imaging, such as MAVRIC (multiacquisition variable resonance image combi­nation) and SEMAC (slice-encoding metal artifact correction), with proton-density weighting or inversion recovery, can also be employed to further reduce susceptibility effects (▶ Fig. 3.3).

One caveat of interpreting the Pfirrmann grading scheme is that to date, no studies have convincingly correlated disc abnormalities on MRI with patients’ symptoms. important to underst and th at T2 signal intensity changes do not directly reflect decreased water content of the disc. A study of cadaveric spines of various ages demonstrated that absolute T2 measurement s correlated more with glycosami­noglycan (GAG) concentration rather than absolute water content. water rather than total water content and as such, the term disc desiccation should be avoided when interpreting disc T2 signal changes. As disc degeneration progresses, the disc may undergo calcification that typically appears as i nternal regions of low signal intensity. However, the type and con­centration of calcification impact signal intensity; concentra­tions of particulate calcium of up to 30% by weight may in fact shorten T1 relaxation times and result in T1 signal hyperintensity of the disc.

sequence that employs a lower Larmor frequency to permit the detection of low-frequency physiochemical interactions between water and extracellular matrix (ECM) molecules.

Annulus disruption, by conventional wisdom, is the initial mechanism leading to disc degeneration as annular fissures are present in almost all degenerated discs. vated by the recurrent meningeal nerve and thus can be a

fragmented apophyseal bone, or fragmented annular tissue)