Objectives Deep brain stimulation (DBS) of the subthalamic nucleus (STN) can be a highly effective treatment for Parkinson's disease. However, therapeutic efficacy can be limited by inconsistent targeting of this nucleus. It was shown previously that an increase in local field potential (LFP) power over the beta frequency band may provide intraoperative confirmation of STN targeting. Whether the depth of this focal increase also helps predict the depth and voltage chosen for chronic stimulation is tested here.
Methods LFPs were recorded from the contacts of 57 DBS electrodes as the latter were advanced in 2 mm steps from above to below the intended surgical target point in STN.
Results A spectral peak in the bipolar LFP was recorded in the 11–35 Hz band at the lowest contact pair that underwent a steep but focal change during electrode descent in all but three sides. The depth of the initial intraoperative step increase in beta correlated with the depth of the contact independently chosen for chronic DBS (Spearman's rho=0.35, p=0.01). In addition, the absolute difference between the depths of the initial increase in beta and the contact chosen for chronic DBS correlated with the voltage used for chronic stimulation (rho=0.322, p=0.017). Thus more voltage had to be employed if a depth was selected for chronic stimulation that differed from that of the beta generator.
Conclusions Online spectral analysis of LFPs recorded from the DBS electrode may help identify the optimal therapeutic target in the STN region for DBS.
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Funding PB was supported by the Medical Research Council of Great Britain and the DANA Foundation, PL, TF, LUZ and MIH by the Parkinson's appeal, IM-T by a grant from Fondo de Inversion Sanitaria (FIS), Instituto de Salud Carlos III, Spanish Department of Science and Innovation (FI08/00108) and FY by the Uehara Memorial Fundation.
Competing interests PB is a consultant to Medtronic Inc.
Ethics approval This study was conducted with the approval of the the joint ethics committee of the Institute of Neurology and National Hospital for Neurology.
Provenance and peer review Not commissioned; externally peer reviewed.