New Imaging Strategies in Degenerative Disease of the Intervertebral Disks: Functional Spine Imaging

As it does for the brain, functional imaging provides additional clinically valuable information on the spine, especially in the problem of back and neck pain. While conventional anatomic spine imaging demonstrates many abnormalities, such as herniation of the intervertebral disk, with nearly perfect accuracy, it does not effectively distinguish incidental degenerative changes in the disk from those that results in pain production. Functional imaging of the spine, still under development and evaluation, will facilitate the identification of painful disks and the selection of patients for innovative treatments that are presently under development. Functional imaging of the spine includes: MR spectroscopy, fMRI of the spinal cord, diffusion imaging, T2 relaxation time, T1 rho measurement and dynamic imaging. The purpose of this presentation is to review the status of these functional MR techniques. MRS: MR spectroscopy demonstrates tissue constituents that have characteristic resonant frequencies. For the disk, the substances that can be recognized in MR spectra and quantified include lactic acid and glycosaminoglycans. Lactic acid has been documented by direct sampling of the disk in painful degenerating disks. With MRS, the concentration of lactic acid is measured non-invasively. In pilot studies, lactic acid concentration effectively distinguishes symptomatic from asymptomatic degenerating disks.