Subthalamic beta oscillations are attenuated after withdrawal of chronic high frequency neurostimulation in Parkinson's disease

Until now, in human PD subjects, STN LFP recordings were only attainable in the peri-operative period and after short periods of stimulation. For the first time, using an investigational, implanted sensing neurostimulator (Activa® PC + S, Medtronic, Inc.), STN LFPs and motor disability were recorded/assessed after withdrawal of chronic (6 and 12 month) HF DBS in freely moving PD subjects. Beta band power was similar within 14 s and 60 min after stimulation was withdrawn, suggesting that “off therapy” experiments can be conducted almost immediately after stimulation is turned off. After withdrawal of 6 and 12 months of STN DBS, beta band power was significantly lower (P < 0.05 at 6 and 12 months) and off therapy UPDRS scores were better (P < 0.05 at 12 months) compared to before DBS was started. The attenuation in beta band power was correlated with improvement in motor disability scores (P < 0.05). These findings were supported by evidence of a gradual increase in beta band power in two unstimulated STNs after 24 months and could not be explained by changes in lead impedance. This suggests that chronic HF DBS exerts long-term plasticity in the sensorimotor network, which may contribute to a lack of progression in underlying motor disability in PD.