Comparison of surgical and electrodiagnostic findings in single root lumbosacral radiculopathies

To identify the segmental innervation of L‐2–S‐1 muscles, we compared the preoperative electrodiagnostic examinations of 45 patients with single‐level lumbosacral radiculopathies confirmed radiologically and surgically. The electrodiagnostic findings were classified as abnormal only by the needle examination and only if muscles demonstrated active denervation or a marked neurogenic motor unit potential firing pattern. In comparison to other surgical, intraoperative root stimulation, and clinical studies, we found several differences. Overall, there was little overlap among L‐2–4, L‐5, and S‐1 radiculopathies. The tibialis anterior was predominantly L‐5 innervated, the gastrocnemius (medial and lateral head) predominantly S‐1 innervated, and the biceps femoris (short and long head) exclusively S‐1 innervated. The two heads of biceps femoris were not affected in any patients with L‐5 radiculopathy in whom they were examined. These findings help guide both the clinician and surgeon in the diagnosis and treatment of lumbosacral radiculopathies. Muscle Nerve 27: 60–64, 2003