Bilateral Nerve Conduction Studies Must Be Considered in the Diagnosis of Sciatic Nerve Injury Due to Intramuscular Injection

Abstract

Objectives: Although compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes of the nerves are reduced in sciatic nerve injury due to intramuscular injection (SNIII), they may still be higher than the reference values if there is a mild axonal degeneration. In this case, comparing the outcomes of nerve conduction studies of intact and affected lower extremities becomes important. We aimed to determine the role of this comparison in the diagnosis of SNIII. Methods: Patients with SNIII were included. Reference values for lower extremity nerve conduction studies were obtained from healthy participants. Peroneal, posterior tibial, superficial peroneal, and sural nerve conduction studies were performed in both lower extremities. In the first analysis, the CMAP or SNAP amplitude of the nerve was considered abnormal if it was less than the reference value. In the second analysis, the CMAP or SNAP amplitude of the nerve was considered abnormal if it was less than the reference value or <50% of the CMAP or SNAP amplitude obtained from the intact limb nerve. Results: Thirty patients and 31 controls were included in the study. Compared with those found in the first analysis, the number of posterior tibial nerve CMAPs with reduced amplitudes, and the sural and superficial peroneal nerve SNAPs with reduced amplitudes were higher in the second analysis (P = 0.008, P < 0.001, and P = 0.031; respectively). Conclusion: This study showed that nerve conduction studies should be performed in both the intact and affected extremities in SNIII.