Magnetic resonance imaging of entrapment of lumbar nerve roots in spondylolytic spondylolisthesis.

Conventional spin-echo T1-weighted parasagittal magnetic resonance images of fifteen consecutive patients who had spondylolytic spondylolisthesis were evaluated for evidence of impingement of a nerve root, which was indicated by the loss of perineural fat within the foramen. Seventeen of a possible thirty nerve roots appeared to be impinged on at the level of the spondylolisthesis. Thirteen of these seventeen nerve roots were associated with clinical evidence of radiculopathy on the side of the root with impingement. None of the thirteen nerve roots that did not appear to have impingement were associated with clinical evidence of radiculopathy. The association between the impingement of a nerve root as seen on magnetic resonance images and clinical symptoms was significant (p < 0.001). Impingement of the nerve root within the neural foramen appeared to be the cause of the radiculopathy in these patients who had spondylolytic spondylolisthesis, and magnetic resonance imaging was a good method for discrimination between nerve roots that were associated with a radiculopathy and those that were not.