Objective: To assess the effect of Interleaved Stimulation (ILS) in patients receiving subthalamic nucleus-Deep Brain Stimulation (STN-DBS), with Freezing of gait (FOG) unresponsive to medication and conventional stimulation paradigms.

Background: FOG is a disabling symptom of advanced Parkinson’s disease (PD), which is often unresponsive to medications and neurostimulation. ILS of the sub thalamic nucleus-substantial nigra pars reticulata improved FOG in advanced PD. Effect of ILS delivered to the standard STN target on FOG is not well characterised. 

Methods: We conducted a prospective study including PD patients receiving STN-DBS with FOG unresponsive to standard monopolar (frequency 130-150Hz) and low frequency (60Hz) stimulation. FOG was assessed at baseline using the FOG questionnaire. Effect of ILS was assessed using the Stand-Walk-Sit (SWS) test at baseline and 30min after switching to the ILS program. All assessments were carried out in the medication OFF stimulation ON state.

Results: Five patients were recruited. Mean age was 58.2±10.9 years and mean duration of PD was 15.5±4.7 years. Patients were receiving STN-DBS for a mean duration of 27.2±12.9 months. At baseline, all patients had FOG in medication OFF and ON states. Compared to baseline, there was significant reduction in the number of FOG episodes (p=0.012) during SWS, 30min after ILS. There was no improvement in the time taken (p=0.157) or number of steps (p=0.759) on SWS. 

Conclusions: In this pilot study, ILS significantly improved FOG in patients with advanced PD receiving STN-DBS, refractory to conventional and low frequency stimulation. Longer follow-up in larger number of patients is warranted to assess clinical efficacy.

References: 1.Weiss D, Walch M, Meisner C, Fritz M, Scholten M, Breit S et al. Ligral stimulation for axial motor impairment in Parkinson;s disease? A randomised controlled trial. Brain 2013, 136:2098-2108

2. Brosius SN, Gonzalez CL, Walker HC. Reversible improvement in severe freezing of gait from Parkinson’s disease with unilateral interleaved stimulation. Parkinsonism Reltd Disord 2015:1469-70

This work was wholly done at and supported by the Sree Chitra Tirunal Institute for Medical Sciences, Trivandrum, India. The first author is presently Assistant Professor (Neurology) at the All India Institute of Medical Sciences, New Delhi, India.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/interleaved-stimulation-for-freezing-of-gait-in-advanced-parkinsons-disease-a-pilot-study/