Paraspinal electromyography in high lumbar and thoracic lesions.

Abstract

To use needle electromyography in the paraspinal muscles to localize the root level of a radiculopathy. We collected nine cases of clinically proven, isolated high lumbar or thoracic disk herniations of patients who underwent MiniPM. Four were from a prospective study of 114 persons with low back pain (MiniPM had 100% sensitivity to magnetic resonance imaging-documented high disks). In the most medial "S" column, mean MiniPM scores were 0.7 for the level above the radiologically documented lesion; 3.1 at the lesion; and 1.6, 1.6, and 1.1 at the three spinous processes below the lesion. Similar numbers were obtained in the "M" column (slightly lateral), with no significant differences between S and M. Differences were significant between and at the level of the lesion for S (P < 0.06) and M (P < 0.01), and between the lesion level and three levels below for the M column (P < 0.01). These findings suggest that paraspinal electromyography has a higher than previously reported sensitivity for high lumbar lesions. Electromyography using MiniPM can localize some radiculopathies. The individual cases suggest that, consistent with the anatomy of the caudi equina, thoracic lesions and lateral lumbar lesions denervate only at one level, but more central lumbar lesions also denervate distally innervated paraspinal muscles.