Paraspinal mapping. Quantified needle electromyography of the paraspinal muscles in persons without low back pain.

Study Design: This was a case series with intervention performed by masked investigators.

Objectives: To determine values for normal subjects on quantified needle electromyography of the paraspinal muscles compared with a previous sample of patients with clear evidence of radiculopathy.

Summary Of Background Data: Diagnosis of radicular back pain is difficult, even with modern imaging studies, partly due to the large percentage of imaging abnormalities in asymptomatic persons. Electromyography has been shown to be as sensitive as imaging studies in diagnosing radicular pain. An electromyographic study of the low back has never been done in normal subjects. We have previously anatomically validated and clinically demonstrated a method of quantitative needle electromyography in the paraspinal muscles called paraspinal mapping.

Methods: Thirty-five subjects free of back pain or polyneuropathy were intermixed with volunteers referred for electromyography of radicular back pain. One electrodiagnostician punctured the skin at five predetermined locations and obtained paraspinal mapping scores in one of these. An electromyographer who was masked to the study's nature then performed a complete paraspinal mapping study. A total "sensitivity" score was compared to scores of previously tested patients who had pain complaints and clear evidence for radiculopathy on either radiologic or traditional electromyographic studies.

Results: Mean score in normal subjects was 1.11 (SD 1.49). Mean score for abnormal subjects averaged 12.18 (SD 12.03). Differences between examiners were insignificant.

Conclusions: Normal persons have few, if any electromyographic abnormalities in the paraspinal muscles. This is in contrast to computed tomography, magnetic resonance imaging, or myelographic results in normal subjects. Persons with radiculopathy have significantly different scores. Needle electromyographic examination of the paraspinal muscles is useful in distinguishing false-positive radiologic studies.