Long term correlation of subthalamic beta band activity with motor impairment in patients with Parkinson's disease.

OBJECTIVES: To investigate the long term association of subthalamic beta activity with parkinsonian motor signs.

METHODS: We recruited 15 patients with Parkinson's disease undergoing subthalamic DBS for local field potential recordings after electrode implantation, and at 3 and 8months post-operatively using the implantable sensing enabled Activa PC+S (Medtronic). Three patients dropped out leaving 12 patients. Recordings were conducted ON and OFF levodopa at rest. Beta (13-35Hz) peak amplitudes were extracted, compared across time points and correlated with UPDRS-III hemibody scores.

RESULTS: Peaks in the beta frequency band (13-35Hz) in the OFF medication state were found in all hemispheres. Mean beta activity was significantly suppressed by levodopa at all recorded time points (P<0.007) and individual beta power amplitude correlated with parkinsonian motor impairment across time points and dopaminergic states (pooled data; ρ=0.25, P<0.001).

CONCLUSIONS: Our results indicate that beta-activity is correlated with parkinsonian motor signs over a time period of 8months.

SIGNIFICANCE: Beta-activity may be a chronically detectable biomarker of symptom severity in PD that should be further evaluated under ongoing DBS.