Could dual-hemisphere transcranial direct current stimulation (tDCS) reduce spasticity after stroke?

Abstract

After providing informed consent, a 61-year-old chronic stroke female patient participated in a double-blind, randomised, placebo-controlled trial to test the potential of transcranial direct current stimulation (tDCS) to improve motor skill learning with the paretic hand. Two years before, she suffered from an ischaemic stroke in the territory of the deep right middle cerebral artery (Fig. 1), leading to left-sided hemiplegia (NIH Stroke Scale: 9). After discharge (modified Rankin Score: 4), she benefited from long-term neurorehabilitation. She recovered walking and partial control of the proximal left upper limb but she had no voluntary finger movements (mRS=3). She developed a severe left-sided spasticity, requiring the daily intake of baclofen 75 mg and tizanidine 4 mg. She was chronically on venlafaxin 75 mg, lorazepam 0.5 mg, aspirin, atorvastatin and ranitidine. The treatment was not modified during the whole experiment. She participated in two experimental sessions separated by 2 weeks, each composed of two distinct parts. During the first part (Intervention session), she performed training on the circuit with dual-tDCS application (real or sham). Two versions (similar difficulty) of the circuit were used for the two Intervention sessions. During the second part (Recall session), which took place 1 week apart, the patient performed the same circuit as during the previous ‘‘Intervention session’’ to test the retention of the motor skill. The Recall session consisted of two evaluations (5 min apart) of the motor skill (duration: 5 min, alternating 30-s blocks of testing and rest). She sat in front of a computer screen; the computer mouse was taped in her left hand. A circuit was displayed on the screen, she was instructed to move the cursor as fast as possible over the circuit, and as precisely as possible by keeping the cursor within the boundaries of the track [1]. During the Intervention session, training was provided during 30 min, alternating blocks of 30 s of practice and rest. Performance was evaluated before (Baseline), during, and up to 60 min after, and 1 week later (Recall). Velocity and accuracy were extracted to compute a performance index (PI) involving a speed/accuracy trade-off. The evolution of the PI from Baseline was expressed as a learning index (LI): LI = [(PI PI baseline)/PI baseline] 9 100. An increment of LI reflects a performance improvement relative to ‘‘Baseline’’ [1]. LI was computed on each circuit block. Before training, she received a short familiarisation with a simple square circuit. During training, dual-tDCS was applied over both primary motor cortices (M1), with anodal stimulation over the ipsilesional M1 and cathodal stimulation over the contralesional M1. The M1 were located using the C3 and C4 positions of the 10-20 EEG system. Real (30 min) and sham (45 s) dual-tDCS were applied with an Eldith DC-Stimulator (NeuroConn, Ilmenau, Germany) in a randomised, double-blind fashion. DualtDCS was delivered via two soaked (NaCl 0.9 %) electrodes (35 cm) at an intensity of 1 mA (fade in/out 8 s). During the first experimental session, she was allocated to receive real dual-tDCS; motor performance and longterm retention of the motor skill markedly improved Y. Vandermeeren (&) S. Lefebvre P. Laloux Department of Neurology, CHU UCL Mont-Godinne, Universite catholique de Louvain (UCL), Avenue Dr G. Therasse, 5530 Yvoir, Belgium e-mail: yves.vandermeeren@uclouvain.be