Objective: To assess the effects of 2mA transcranial Direct Current Stimulation (tDCS) over the affected Parietal-Insular-Vestibular Cortex (PIVC) on seated posture of patients with lateropulsion following stroke. We hypothesized that bilateral electrode placement over PIVC (vs active control) would produce a change in seated posture.
Background: Lateropulsion following stroke (Pusher Syndrome) is characterized by lateral displacement of subjective postural vertical toward the weak side. It is caused by lesions affecting vestibular projections to the Ventral Lateral Thalamus (VLT) or projections from the VLT to the Parietal-Insular-Vestibular Cortex (PIVC).
Methods: Seventeen subjects with Burke Lateropulsion Scale scores ≥ 2 within 30 days of an ischemic stroke signed an IRB-approved consent. They received 2mA tDCS delivered using 25cm2 saline soaked sponge electrodes via one of two montages: Test (anode over the affected PIVC and cathode opposite PIVC) versus Active Control (anode over the affected PIVC and cathode over the opposite supra-orbital region). PIVC was defined using EEG 10/20 coordinates. Seated medial-lateral center of pressure (COP-X) was measured using a custom-designed chair mounted on an AMTI™ analog-to-digital forceplate. An inclinometer strapped to the chest and aligned with the sternum measured lateral trunk tilt. Data were collected prior to, then at 5, 10, and 15 minutes during tDCS and 5 min following tDCS.
Results: Repeated Measures Analysis of Variance rejected the hypothesis of an interaction between Montage and Time for: mean COP-X displacement (in) (Wilks’ λ F = 0.647 df=(4, 13), P= 0.639); mean speed of COP-X (in/s) (Wilks’ λ F = 0.740 df=(4, 13), P=0.581); mean inclinometer tilt (degrees) (Wilks’ λ F = 0.740 df=(4, 13), P=0.581).
Conclusion: Neither tDCS montage showed improvement in COP-X displacement, COP-X movement velocity or inclinometer readings. These negative results are important to encourage the development of alternative tDCS stimulation parameters or identification of alternative cortical or vestibular tDCS targets for the treatment of Lateropulsion Following Stroke.