Somatomotor mu rhythm amplitude correlates with rigidity during deep brain stimulation in Parkinsonian patients

Abstract

Objective: Parkinsonian patients have abnormal oscillatory activity within the basal ganglia-thalamocortical circuitry. Particularly, excessive beta band oscillations are thought to be associated with akinesia. We studied whether cortical spontaneous activity is modified by deep brain stimulation (DBS) in advanced Parkinson's disease and if the modifications are related to the clinical symptoms.

Methods: We studied the effects of bilateral electrical stimulation of subthalamic nucleus (STN) on cortical spontaneous activity by magnetoencephalography (MEG) in 11 Parkinsonian patients. The artifacts produced by DBS were suppressed by tSSS algorithm.

Results: During DBS, UPDRS (Unified Parkinson's Disease Rating Scale) rigidity scores correlated with 6-10 Hz and 12-20 Hz somatomotor source strengths when eyes were open. When DBS was off UPDRS action tremor scores correlated with pericentral 6-10 Hz and 21-30 Hz and occipital alpha source strengths when eyes open. Occipital alpha strength decreased during DBS when eyes closed. The peak frequency of occipital alpha rhythm correlated negatively with total UPDRS motor scores and with rigidity subscores, when eyes closed.

Conclusion: STN DBS modulates brain oscillations both in alpha and beta bands and these oscillations reflect the clinical condition during DBS.

Significance: MEG combined with an appropriate artifact rejection method enables studies of DBS effects in Parkinson's disease and presumably also in the other emerging DBS indications.