Evaluation of fatty degeneration of paraspinal muscle on computed tomography

It is well known that fatty degeneration of muscles of the trunk and extremities is noticed in many myogenic and neurogenic disorders. This kind of muscle atrophy also occurs in the paraspinal muscle. We report fatty degeneration of the paraspinal muscle in the intervertebral disk hernia on computed tomography (CT). In 77 cases of disk hernias, 20 cases (26 %) show fatty degeneration on CT. We analysed CT pattern of these 20 cases and two characteristic findings were found as a result. One is that fatty degeneration of the paraspinal muscle should result from continuous compression of the nerve roots by the extruded disk hernia. The other is that the multifidus muscle appears to be more easily damaged than the sacrospinal muscle. In other words, the medial branch of the dorsal spinal nerve is weaker than the lateral branch against the mechanical compression. Although the clinical significance of fatty degeneration of the paraspinal muscle is not obvious, we mentioned the possibility that fatty degeneration has some role in residual low back pain after the surgery. (author)