Introduction. Radicular low back pain is one of the most common medical problems. The aim of this study was to evaluate the diagnostic accuracy of MRI and electrodiagnosis in lower extremity radicular pain in relation to history and clinical findings. Methods. In this cross-sectional study, we studied 165 sciatalgic subjects. A comprehensive history and physical examinations were taken from the subjects and recorded, and then MRI scanning and electrodiagnostic (nerve conduction velocity and electromyography) tests were performed. Results. From 152 subjects who remained in the study, 67 cases (44.1%) had radicular pain in left lower limb, 46 (30.3%) in right, and 39 (25.6%) in both lower limbs. 104 cases (68.4%) had shown some type of abnormalities in both MRI and electrodiagnosis, 30 (19.7%) had shown this abnormality only in MRI, and 21 (13.8%) only in electrodiagnosis, while 10 cases (6.5%) had both normal MRI and electrodiagnostic studies. Coordination rates of MRI and electrodiagnosis with clinical findings were 58.6% and 89.5%, respectively. Conclusion. In many MRI negative but symptomatic subjects, electrodiagnosis has an important diagnostic value. 1. Introduction Radicular low back pain is one of the most common medical problems that cause decreased work competence and a heavy cost. Accurate diagnosis of this radicular pain has a paramount important role in proper treatment planning [1]. History taking and physical examination are the first steps in diagnosis of lower extremity radicular pain [2]. In clinical examination of these patients, in addition to the radicular pain, reduced muscle strength, a sensory deficit, and decreased deep tendon reflexes are reported [3]. The use of imaging techniques such as magnetic resonance imaging (MRI) is indicated in the patients with atypical or refractory complains to confirm the clinical diagnosis or help to select the proper approach if surgery is necessary [4]. Despite the accuracy of the history, physical examination and MRI in the lower extremity radicular pain, in some cases for more accurate diagnosis, other diagnostic measures are also needed. Although MRI has sufficient accuracy in the diagnosis of some nondiscogenic sciaticas such as spinal tumors, epidural varicosis, and infectious spinal stenosis, it is incapable of diagnosis in many far out (extraforaminal) spinal stenosis lesions. Electrodiagnostic tests can especially provide useful information about the exact location of the nerve damage [5]. Among all the electrodiagnostic studies, electromyography (EMG) technique has a very high accuracy
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