title: Bihemispheric-tDCS and Upper Limb Rehabilitation Improves Retention of Motor Function in Chronic Stroke: A Pilot Study.
abstract: BACKGROUND
  Single sessions of bihemispheric transcranial direct-current stimulation (bihemispheric-tDCS) with concurrent rehabilitation improves motor function in stroke survivors, which outlasts the stimulation period. However few studies have investigated the behavioral and neurophysiological adaptations following a multi-session intervention of bihemispheric-tDCS concurrent with rehabilitation.
  
  
  OBJECTIVE
  This pilot study explored the immediate and lasting effects of 3-weeks of bihemispheric-tDCS and upper limb (UL) rehabilitation on motor function and corticospinal plasticity in chronic stroke survivors.
  
  
  METHODS
  Fifteen chronic stroke survivors underwent 3-weeks of UL rehabilitation with sham or real bihemispheric-tDCS. UL motor function was assessed via the Motor Assessment Scale (MAS), Tardieu Scale and grip strength. Corticospinal plasticity was indexed by motor evoked potentials (MEPs), cortical silent period (CSP) and short-interval intracortical inhibition (SICI) recorded from the paretic and non-paretic ULs, using transcranial magnetic stimulation (TMS). Measures were taken at baseline, 48 h post and 3-weeks following (follow-up) the intervention.
  
  
  RESULTS
  MAS improved following both real-tDCS (62%) and sham-tDCS (43%, P < 0.001), however at 3-weeks follow-up, the real-tDCS condition retained these newly regained motor skills to a greater degree than sham-tDCS (real-tDCS 64%, sham-tDCS 21%, P = 0.002). MEP amplitudes from the paretic UL increased for real-tDCS (46%: P < 0.001) and were maintained at 3-weeks follow-up (38%: P = 0.03), whereas no changes were observed with sham-tDCS. No changes in MEPs from the non-paretic nor SICI from the paretic UL were observed for either group. SICI from the non-paretic UL was greater at follow-up, for real-tDCS (27%: P = 0.04). CSP from the non-paretic UL increased by 33% following the intervention for real-tDCS compared with sham-tDCS (P = 0.04), which was maintained at 3-weeks follow-up (24%: P = 0.04).
  
  
  CONCLUSIONS
  bihemispheric-tDCS improved retention of gains in motor function, which appears to be modulated through intracortical inhibitory pathways in the contralesional primary motor cortex (M1). The findings provide preliminary evidence for the benefits of bihemispheric-tDCS during rehabilitation. Larger clinical trials are warranted to examine long term benefits of bihemispheric-tDCS in a stroke affected population.
authors.affiliation: Institute for Physical Activity and Nutrition, Deakin University Melbourne, VIC, Australia.
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Goodwill
authors.affiliation: Institute for Physical Activity and Nutrition, Deakin University Melbourne, VIC, Australia.
authors.forename: Wei-Peng
authors.initials: WP
authors.lastname: Teo
authors.affiliation: Department of Physiotherapy, Faculty of Medicine, Nursing and Health Science, Monash University Frankston, VIC, Australia.
authors.forename: Prue
authors.initials: P
authors.lastname: Morgan
authors.affiliation: Institute for Physical Activity and Nutrition, Deakin University Melbourne, VIC, Australia.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Daly
authors.affiliation: Department of Rehabilitation, Nutrition and Sport, School of Allied Health, La Trobe University Melbourne, VIC, Australia.
authors.forename: Dawson J
authors.initials: DJ
authors.lastname: Kidgell
keywords: bihemispheric-tDCS; chronic stroke; corticospinal excitability; intracortical inhibition; motor function; rehabilitation