Significance and Natural History

      The determination of clinically significant disk disease is an important radiologic and clinical decision because the possible consequences of back surgery are not insignificant. Identification of nerve root compression or severe effacement of the thecal sac, especially ventrolaterally, that correlates with radicular pain or a muscle weakness pattern supports the operative approach when conservative medical therapy has failed. But beyond that, things are less certain. Annular tears and focal disk protrusions are frequently found in asymptomatic populations. The annuloligamentous complex is richly innervated by the recurrent meningeal nerve. Annular tears involving this complex may be a source of diskogenic pain due to exposure of the nerve endings to the acid metabolites of the protruding nucleus pulposus. Endnote

      Jensen and his group Endnote detected MR signs of intervertebral disk disease, consisting of bulge, protrusion, or extrusion, in 64% of asymptomatic adult subjects. Moreover, disk herniation does not relate directly to back pain or a radicular pain syndrome. In a study by Boden and colleagues, Endnote lumbar disk herniations were found in 28% of asymptomatic patients over 40 years of age.

      Furthermore, patients with symptomatic disk herniations don't necessarily require surgery. Bozzao and colleagues Endnote followed 69 patients with herniated lumbar disks for 6 to 15 months while they were under conservatively medical therapy. On follow-up MR imaging, 63% showed a reduction in size of their herniated disk of more than 30%, 48% showed a reduction of more than 70%, and only 8% got worse or enlarged. Larger herniations were more likely to decrease, which they attributed to more vascularity or granulation tissue. The excellent depiction of abnormal morphology by MR imaging provides an opportunity to investigate further the natural history of intervertebral disk disease. Endnote  

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