The value of the internal capsule signs in the stimulation of the subthalamic nucleus in Parkinson's disease

The effectiveness of stimulating the subthalamic nucleus (DBS-STN) in advanced Parkinson's disease (PD) largely depends on the correct placement of the electrodes. Since the sensory-motor region of the STN lies beside the internal capsule (IC), we believe that the motor effectiveness of DBS-STN could be related to the stimulation threshold in which IC signs appear (IC threshold). An examination of 17 consecutive patients with advanced PD who had been submitted to bilateral DBS-STN (one case was unilateral) was carried out to determine the motor improvement on each side of the body (n = 33) and the energy consumption one year after surgery according to the IC threshold obtained during the programming. A 45% improvement was observed in the UPDRS III in off and there was a 24% reduction in the equivalent dose of levodopa with bilateral DBS-STN. When the electrodes were considered, there was a statistically significant improvement that depended on the IC threshold. Energy consumption differed significantly between electrodes with an IC threshold of 3-7 V (1.5 +/- 1.2 microW) and those with an IC threshold > 7 V (8.3 +/- 9.4 microW). During the stimulation phase and following the correct location of the STN, which was achieved by neurophysiological recording, the IC threshold has prognostic implications in medium-long term motor effectiveness and in the consumption of the battery in the generator.