Effects of deep brain stimulation frequency on bradykinesia of Parkinson's disease

Deep brain stimulation (DBS) in Parkinson's disease (PD) is frequency-dependent. Past studies of the effect of DBS frequency, however, involved scrutiny of too few frequencies to eliminate risk of undersampling. Also, these studies presented averaged measures across subjects; high intersubject variability makes these measures problematic. In this study, 6 subjects with PD were tested in a drug-minimal state. Following 10 minutes of stimulation at the new frequency, all available frequencies were tested. Hand-opening and hand-closing amplitude and frequency were measured in 3 epochs of 15 seconds each. Multiple frequencies (low and high) resulted in peaks of increased movement amplitudes. Peaks were specific and varied among individuals. No clear relationship between stimulation frequency and movement frequency was discovered. In light of the findings, a wider range of stimulation frequencies should be examined, particularly lower frequencies. Most current theories of PD pathophysiology and DBS mechanisms of action fail to explain results of the kind demonstrated herein.