Paraspinal electromyographic abnormalities as a predictor of occult metastatic carcinoma

Profound membrane irritability localized primarily to the paraspinal muscles was the major electromyographic criterion proposed by LaBan and associates to predict the early presence and localization of spinal metastatic disease. A retrospective review was recently conducted to determine the accuracy of this interpretation and the effect of the electromyographic report on the attending physician's subsequent workup. In an analysis of 1800 electromyograms at Riverside Hospital, 91 cases were found which met the following criteria: (1) three or more paraspinal segments involved, (2) little or no membrane irritability in the anterior rami, and (3) no previous surgery on the paraspinal area. The proven discharge diagnoses were carcinoma in 24%, herniated nucleus pulposus in 28%, degenerative disc disease in 16%, diabetes mellitus in 9% and miscellaneous in 8%; in 15% no diagnosis could be made. We were unable to differentiate some cases of herniated nucleus pulposus from carcinoma using such criteria as profoundness of levels or number of spinal segments involved. There are partial explanations of why only paraspinal segments may be involved with profound changes in the diseases mentioned, but no explanation for the widespred involvement in localized disease such as a herniated disc. At our hospital it was interesting to note that internists infrequently order myelography or cerebrospinal fluid analysis while orthopedists, neurosurgeons and neurologists rarely order metastatic surveys.