Cervical Spine

      Cervical disk disease occurs most commonly at the levels of C5-6 and C6-7. A central disk herniation will most likely cause a myelopathy due to cord compression, along with neck pain and stiffness. If the disk extends laterally to compress nerve roots, the pain may radiate to the shoulder, arm, or hand.

      A sagittal T1 study shows the margins of the spinal cord with respect to other structures within the spinal canal. Subtle scalloping of the cord may be present due to encroachment posteriorly by ligamentum flavum hypertrophy or anteriorly by disk or spondylosis. Because disk, ligaments, and bone have low or absent signal on T1-weighted images, it may not be possible to differentiate these structures from one another. The increased contrast between the CSF containing thecal sac and adjacent structures on T2-weighted FSE or GRE images improves visualization of extradural lesions that impinge on the thecal sac. Endnote

      Degeneration of the intervertebral disk is accompanied by loss of water content and therefore signal intensity on MR images. Loss of disk signal is not a necessary prerequisite for disk herniation. On T1 images a herniated disk generally has the same signal characteristics as the parent disk and is seen as an extrusion of disk material into the spinal canal. Endnote Herniated disks can be midline or lateral, and it is important to clearly identify the location of the disk fragment for surgical planning. Endnote Midline extradural lesions can be identified on sagittal views by effacement of the thecal sac or cord, but when eccentric they may be seen better on the axial views. Normal signal intensity in the neural foramina may be diminished due to displacement of either epidural veins or foraminal fat.

      High-signal above and below a herniated disk is frequently seen and most likely represents flow enhancement in engorged epidural veins containing slowly flowing blood. On parasagittal scans, flow enhancement in these veins may be the best indicator of an epidural abnormality when a central component is absent.

      Indentation or compression of the cord is common with larger disks and is seen best on T2-weighted or gradient-echo sagittal images. When either herniated disks or osteophytes impinge on the spinal cord, cord injury can result, which points out the importance of prompt, accurate diagnosis and definitive therapy. As with any contusion, cord edema and swelling develop that may be seen as focal high-signal intensity on T2-weighted scans. There is also disruption of the blood-cord barrier, so enhancement may be observed with Gadolinium. 

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