Does stimulation of the GPi control dyskinesia by activating inhibitory axons?

A 69-year-old woman with Parkinson's disease and levodopa-induced dyskinesi as had a deep brain stimulation (DBS) electrode inserted into the right glo bus pallidus internus (GPi). During the operation, the GPI was mapped with dual microelectrode recordings. Stimulation through one microelectrode in G PI inhibited the firing of GPi neurons recorded with another microelectrode 600-1.000 mum distant. The inhibition could be obtained with pulse widths of 150 mus and intensities as low as 10 muA. Single stimuli inhibited GPI n eurons for similar to 50 ms. Trains of 300 Hz stimuli inhibited GPi neuron firing almost completely. Postoperatively. stimulation through macroelectro de contacts located in the posterior ventral pallidum controlled the patien t's dyskinesias. The effect could be obtained with pulse widths of 50 mus a nd frequencies as low as 70-80 Hz. We postulate stimulation of the ventral pallidum controls dyskinesias by activating large axons which inhibit GPi n eurons. (C) 2001 Movement Disorder Society.