Specificity of needle electromyography for lumbar radiculopathy in 55- to 79-yr-old subjects with low back pain and sciatica without stenosis.

Abstract

The aim of this study was to determine the specificity of needle electromyography for lumbar radiculopathy in subjects with low back pain and sciatica without stenosis. Subjects 55 yrs or older with diagnoses of low back pain and sciatica underwent a standardized monopolar needle evaluation by blinded electromyographers as part of a spinal stenosis study. The presence or absence of radiculopathy was determined using different electrodiagnostic criteria. Seventy-two subjects with a mean age of 64.6 years (SD, 7.0 yrs) were studied. When only positive sharp waves or fibrillations were considered abnormal, most of the diagnostic criteria--two limb muscles + associated lumbar paraspinal muscle abnormal, two limb muscles abnormal, or one limb muscle + associated lumbar paraspinal muscle abnormal--had 97%, 96%, and 92% specificity, respectively. When 30% or greater polyphasia in the limb muscles was also considered abnormal, the respective specificities were 90%, 81%, and 85%. When 20% or greater polyphasia in the limb muscles was also considered abnormal, the respective specificities were 90%, 74%, and 71% [corrected]. There is good specificity for lumbosacral radiculopathy when appropriate diagnostic criteria are used.