P-112 Virtual reality induced gait manipulation affects cortico- subthalamic networks in parkinsonian patients

Obective: The aim is to characterize subcortico-cortical network activity changes in Parkinson’s disease (PD) patients during manipu- lation of gait symmetry in a virtual environment (VR). Background: Gait disorder and freezing of gait (FOG) represent a poorly understood symptom complex in PD. Recent observations of different FOG subtypes (Ehgoetz Martens et al., 2018) underline the importance of gait asymmetry, which is strongly related to FOG severity (Plotnik and Hausdorff, 2008). Enhancing gait symme- try is proved to be a potential therapeutic approach of FOG (Frazzitta et al., 2013).
Methods: PD patients with chronically implanted subthalamic deep brain stimulation (STN DBS) systems with ‘‘sensing” neurostimula- tors (PerceptTM, Medtronic) performed a stepping task in a supine position on a custom-made stepping device in a first-person view VR presented via head-mounted display (Vive, HTC). The VR was exploited to modulate the step length by individually spaced mark- ers on the floor. Markers appeared either symmetrically or shortened to 65% for one leg to induce asymmetric stepping pattern. Simultaneous recordings of 24-channel EEG (Smarting, mBrainTrain), bilateral subthalamic LFPs, movement sensors attached to both legs (CMS20, Zebris) and pupillometry (VR binocu- lar Add-on, Pupil labs), were performed to capture multi-site net- work activity changes.
Clinical assessment consists of gait parameters measured using GAITRite! electronic walkway system, MDS_UPDRS III and Zieglers test performed in medication (Med) OFF/STN DBS (Stim) OFF, Med OFF/Stim ON and Med ON/Stim ON. Furthermore, questionnaires (MDS UPDRS I, II, IV, FOG-Q, FOG-C) and a cognitive test (MoCA) are conducted.
Oscillatory properties of LFPs, EEG and pupillometry are assessed referring to gait events.
In this ongoing trial, 7 PD patients (6 male, 1 female, age 64.4±6.2, disease duration 14.1±8.8 yrs.) were assessed 2.7±4.5 years after STN DBS implantation.
Results: MDS UPDRS improved in STIM ON MED ON (21.6±15.4) by 46% and STIM ON MED OFF (31±13.3) by 24.2% compared to STIM OFF MED OFF (40±14.6). Preliminary findings indicate a decrease in beta power between stepping and resting condition and a slight increase during stepping irregularities.
Conclusions: Simultaneous recording of synchronized LFPs, EEG, pupillometry and accelerometry is feasible in this experimental set- ting and the VR induced gait modulation seems to have an impact on beta-band gait network activities.