Describing paraspinal EMG findings: inadequacy of the single 0-4+ score

Clinical electrodiagnostic textbooks instruct that lumbar radiculopathies typically have paraspinal abnormalities and that these abnormalities should be recorded using a single 0-4+ scale. Recent work demonstrates that that the innervation of the paraspinal muscles is segmental, not homogenous, and that asymptomatic persons may have reproducible ("1+") positive waves or fibrillation potentials.

To assess current use of the 0-4+ scale, a retrospective study of EMG scores in persons diagnosed with radiculopathy at a university laboratory was performed. No specific paraspinal EMG technique was used. Included were 117 consecutive, qualified S-1 radiculopathies and 33 L-5 radiculopathies.

When radiculopathy was defined by "more than one limb muscle abnormal," paraspinal scores were recorded as 0 to 1+ in 83% of L-5 and 63% of S-1 cases (chi2, L-5 vs. S-1, not significant). For more severe radiculopathies (at least one limb muscle with a "2+" score), 0-1+ paraspinal scores were recorded in 76% of L-5 and 57% of S-1 cases (chi2, not significant). A total of 82% of S-1 radiculopathies with no overlapping L-5 innervation had 0-1+ scores.

These data demonstrate the common use of equivocal paraspinal scores in patients whom electromyographers believe have radiculopathies. Standardized exploration techniques and a more detailed scoring system for the paraspinal muscles may eliminate this discrepancy.