Prediction of lower extremity strength by nerve conduction study in cauda equina syndrome

Abstract

An electrodiagnostic test is more useful than the lower extremity isometric strength test for objectively determining the degree of nerve damage and prognosis in cauda equina syndromes (CES). This study evaluated the correlation between nerve conduction study (NCS) parameters and the lower extremity isometric strength and manual muscle test (MMT) grades. The isometric strengths of knee extension (KE), ankle dorsiflexion (ADF), and ankle plantarflexion (APF) were measured. NCS parameters, MMT, and isometric strength of femoral, peroneal, and tibial nerves were evaluated, including their correlations with each other. A regression equation between the isometric strength and compound muscle action potential (CMAP) amplitudes was derived and cutoff values were used to confirm boundary values of strength and amplitude between the MMT grades. KE isometric strength and femoral nerve CMAP amplitude were significantly correlated (r = 0.738, P