Comparison of motor conduction abnormalities in lumbosacral radiculopathy and axonal polyneuropathy

We compared the frequencies and types of motor conduction abnormalities fou nd in peroneal and tibial nerves of patients with either L5/S1 radiculopath ies (n = 47) or axonal polyneuropathies (n = 49). In axonal neuropathies, c ompound muscle action potentials (CMAPs) were more likely to be either unob tainable or, if present, of low amplitude, prolonged in distal latency or b oth. F responses were more often absent, impersistent, or prolonged in mini mal latency, In contrast, CMAPs in lumbosacral radiculopathies were more li kely to be normal in both amplitude and distal latency. The most frequent F -response abnormality in radiculopathies was a prolonged maximum-minimum la tency range rather than abnormalities of minimal latency or persistence. Lo gistic regression analysis demonstrated that different patterns of motor co nduction abnormalities result from lumbosacral radiculopathy and distal axo nopathies. The model was able to correctly classify disease state in 76% of subjects with a sensitivity of 74% and specificity of 80%. (C) 1999 John W iley & Sons, Inc.