Objective: To demonstrate that there are interindividual differences in the response of upper limb bradykinesia to subthalamic deep brain stimulation (STN-DBS) in patients with Parkinson’s disease (PD) depending on the stimulation frequency used.

Background: There is evidence that increasing stimulation frequency of STN-DBS beyond the standard settings of 130 Hz may improve tremor, whereas lower frequencies <100 Hz are more beneficial for axial motor symptoms. There are also indications that the improvement of upper limb motor symptoms varies between patients depending on the frequency used.

Method: A kinematic analysis of a finger-tapping train for 20 sec. was assessed in 13 PD patients (median: 63 ears; range 56-71 years) with chronic (> 3 months) bilateral STN-DBS after overnight PD drug withdrawal. Frequencies were varied in intervals of 10 Hz from 60-180 Hz (randomized sequence), while the TEED was kept stable. Every train of finger-tapping was performed twice for each frequency five minutes after the frequency had been changed. The decrement of the amplitude of the finger taps (i.e. distance between index finger and thumb) was measured by means of a kinematic system and estimated by fitting a regression line to the amplitude values. The regression coefficients were compared statistically.

Results: As expected the amplitude decrement of finger taps improved under DBS compared to the state off DBS (p<0.001). The optimal stimulation frequency with the least decrement varied from patient to patient. There was no consistent peak frequency across patients.  Similar observations were made for the worst stimulation frequencies which in a few patients resulted in an even worse motor performance than off DBS

Conclusion: Our results indicate that the effect of DBS on upper limb bradykinesia varies across individuals depending on the frequency used. The standard frequency of 130 Hz may not yield the best motor response to DBS in all individuals. We propose that evaluating different stimulation frequencies may contribute to an optimisation of the DBS effect, whereas the concept of “one frequency fits all” should be abolished.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/frequency-dependent-interindividual-variability-of-the-deep-brain-stimulation-effect-on-upper-limb-bradykinesia/