Irene di Giulio – Abstract

Effect of STN-DBS frequency on postural performance in Parkinson’s disease

Di Giulio I[1,2], Kalliolia E[1,3], Georgiev D[1,4], Peters AL[1], Voyce DC[1], Akram H[1], Foltynie T[1], Limousin P[1], Day BL[1]

  1. Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK.
  2. School of Basic and Medical Biosciences, King’s College London, London, UK.
  3. St. Luke’s Hospital Thessaloniki, Greece.
  4. Ljubljana University Medical Centre, Ljubljana, Slovenia.

Postural instability is a debilitating motor symptom in Parkinson’s disease (PD). Deep-brain stimulation (STN-DBS) may help initially, but its efficacy decreases in the years following surgery (1-3). We hypothesise that bespoke tuning of STN-DBS frequency will improve postural performance in chronically stimulated patients.

Methods: The effect of stimulation frequency (40 to 140Hz, 20Hz-steps) on postural performance was assessed in 24 PD patients treated with STN-DBS for more than 4 years. Forward and backward shoulder pulls were delivered using two force-feedback-controlled motors (4). Outcome measures were antero-posterior ground force (FAP) to gentle pulls, step length to strong pulls, and back length during pre-pull standing as an indicator of stoop. These measures were analysed statistically to establish optimal frequency(ies) for each patient’s postural performance.
Results: Most patients showed best FAP with STN-DBS set to 100 and 120Hz (21 patients), while the first step was longer at 80Hz (20 patients). The back was less stooped at 100Hz (10 patients). When an optimal frequency was sought that improved one measure without deteriorating the others, 10 patients optimised at 100Hz, 5 patients at 80Hz and 5 patients at120Hz.

Conclusions: Postural performance in PD is dependent on STN-DBS frequency, although not all aspects of performance necessarily improve at the same frequency. Lowering the stimulation frequency from the common post-surgery setting of 130Hz to 100Hz may help to reduce postural problems associated with chronic stimulation and disease progression.

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