RESUMO
The clinical differentiation between lumbosacral radiculopathy and generalized peripheral neuropathies of the distal-axonal type is often difficult. In such cases, the electromyographer relies on the presence of paraspinal or proximal muscle denervation and normal sensory conduction studies to indicate radicular disease. These criteria are often is inadequate, such as in elderly patients, when amplitudes of sensory nerve action potentials may be reduced as an age-related phenomenon. So if motor conduction changes in lumbosacral radiculopathy and generalized peripheral neuropathies are adequately described, a useful electrodiagnostic criterion for differentiation of radiculopathy and neuropathy will be available. Patients were entered in this study that met strict clinical and electrophysiological criteria for L5/S1 lumbosacral radiculopathy or generalized peripheral neuropathies of the distal-axonal type. The distal axonopathy group consisted of 19 men and 17 women, and lumbosacral radiculopathy group consisted of 28 men and 22 women. To minimize classification errors resulting from age-related changes, we excluded patients older than 60 years. Lower limbs of all patients were examined, recorded parameters included compound muscle action potential [CMAP] amplitude, distal latencies and conduction velocities; minimal, mean and maximal latencies of F-waves, and maximum-minimum latency ranges, and persistence of F waves of tibial and deep peroneal nerves. The mean values of minimal, mean and maximal latencies of F-waves of tibial and deep peroneal nerves in neuropathy group were significantly more prolonged than lumbosacral radiculopathy group [p<0.001]. The mean CMAPs amplitudes and persistence of tibial and deep peroneal nerves F-waves in neuropathy group were lower than lumbosacral radiculopathy group [p<0.001], but mean latency range of F-waves for both nerves in lumbosacral radiculopathy group were significantly more prolonged, [p<0.001], that this prolongation is more significant in deep peroneal nerves [p=0.004]. In young persons that significant decrease of SNAPs amplitude can reliably help to decision, mere dependence to motor conduction studies is not necessary. Also when there is denervation in proximal muscles that innervated by L5-S1 roots, the radiculopathy is more probable than neuropathy. When a patient is presented with numbness and paresthesia in lower limbs, and sensory nerve conduction or electromyographic studies can not help to decision, in these cases motor nerve conduction studies especially various parameters of F-wave such as; minimal latency, latency range and persistence could be useful