Relationship between muscle abnormalities and symptom duration in lumbosacral radiculopathies.

A long held notion in the electrodiagnostic literature is that paraspinal muscles tend to show electromyographic abnormalities early on in a lumbosacral radiculopathy and that more distal muscles become abnormal later in the disease process. The purpose of this study was to determine whether paraspinal muscles and other major proximal and distal muscle abnormalities are related to lumbosacral radiculopathy symptom duration. A multivariate logit analysis of 139 patients (retrospectively identified) with electrodiagnostically confirmed lumbosacral radiculopathies was used to test these hypotheses. Maximum likelihood estimates showed no evidence of correlation between abnormal paraspinal muscles and symptom duration. Symptom duration was also insignificant for the remaining five lower limb muscles analyzed. We conclude that the probability of having electromyographic abnormalities is not related to symptom duration. A prospective study is needed to confirm these findings. Nonetheless, clinicians should use caution when interpreting electrodiagnostic findings based on symptom duration.