Objective: Characterize the temporal resurgence/amelioration of Parkinsonian rigidity corresponding to withdrawal/application of deep brain stimulation (DBS) therapy.

Background: Rigidity is a cardinal symptom of Parkinson’s disease and is examined clinically to provide diagnosis, track disease progression, and determine treatment efficacy. Therefore, it is important to quantify DBS wash-in/out periods to establish guidelines for clinical practice and future research. Here, we use a clinically validated [1] instrument to ascertain the time course of DBS therapeutic action on rigidity. Briefly, the palm-worn instrument employs a miniature motor to flex the third digit of the hand about the metacarpophalangeal joint whilst embedded transducers record flexion and extension forces. The force required to flex the digit is indicative of rigidity.

Method: Eight participants with Parkinson’s disease receiving benefit from DBS were consented. Participants arrived on-DBS (optimal clinical setting) and off dopaminergic medication. The rigidity instrument was affixed to the palm and a baseline measurement was conducted immediately prior to DBS withdrawal. Rigidity was measured every 10-minutes over a period of 60 minutes to capture rigidity resurgence. DBS was then resumed and rigidity was measured every 5-minutes over a period of 30 minutes to capture amelioration. Data were pooled across patients and means at each time point compared.

Results: Following DBS cessation, rigidity increased gradually to reach a peak at 50 minutes and was significantly greater than baseline (p < 0.01). DBS resumption resulted in an almost immediate improvement of rigidity (p < 0.01), returning to baseline values within five minutes (p = 0.65).

Conclusion: Consistent with clinical observations, rigidity responds to DBS therapy quickly. However, effects of prolonged therapy can take at minimum 50 minutes to wash-out. Adequate rest periods must be enforced between trials to account for wash-out during clinical studies where alternative DBS programs are trialed. Notably, the dichotomy between wash-in/out periods represents a hysteresis effect that may influence closed-loop adaptive DBS.

References: [1] Perera T, et al. A Palm-Worn Device to Quantify Rigidity in Parkinson’s Disease. J. Neurosci Methods, in-press, 2019.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deep-brain-stimulation-wash-in-out-periods-quantified-using-a-palm-worn-device-to-monitor-rigidity/