Electrophysiological effects of lumbar dorsal root stimulation

Electrical stimulation was applied to the L-5 and L-6 dorsal root ganglia of 14 monkeys with concurrent monitoring of cortical and intralaminar thalamic evoked potentials. Both responses were decreased by root stimulation, although cortical suppression required current levels 50 to 100% higher. The evoked potentials remained suppressed for periods of up to 60 minutes after 10- to 15-minute stimulation of the lumbar root electrodes. There was no increase in the duration of transmission block with longer stimulation periods. These results and available clinical data suggest that a local conduction block may be responsible for the pain relief produced by peripheral electrical stimulation. Further studies to identify more precisely the neural systems affected are required.