Symmetry of paraspinal muscle denervation in clinical lumbar spinal stenosis: support for a hypothesis of posterior primary ramus stretching?

INTRODUCTION Denervation of the paraspinal muscles in spinal disorders is frequently attributed to radiculopathy. Therefore, patients with lumbar spinal stenosis causing asymmetrical symptoms should have asymmetrical paraspinal denervation. METHODS Seventy-three patients with clinical lumbar spinal stenosis, aged 55-85 years, completed a pain drawing and underwent masked electrodiagnostic testing, including bilateral paraspinal mapping and testing of 6 muscles on the most symptomatic (or randomly chosen) limb. RESULTS With the exception of 10 subjects with unilateral thigh pain (P = 0.043), there was no relationship between side of pain and paraspinal mapping score for any subgroups (symmetrical pain, pain into 1 calf only). Among those with positive limb EMG (tested on 1 side), no relationship between side of pain and paraspinal EMG score was found. CONCLUSION Evidence suggests that paraspinal denervation in spinal stenosis may not be due to radiculopathy, but rather due to stretch or damage to the posterior primary ramus.