Transcranial direct current stimulation for the treatment of motor impairment following traumatic brain injury

Abstract

After traumatic brain injury (TBI), motor impairment is less common than neurocognitive or behavioral problems. However, about 30% of TBI survivors have reported motor deficits limiting the activities of daily living or participation. After acute primary and secondary injuries, there are subsequent changes including increased GABA-mediated inhibition during the subacute stage and neuroplastic alterations that are adaptive or maladaptive during the chronic stage. Therefore, timely and appropriate neuromodulation by transcranial direct current stimulation (tDCS) may be beneficial to patients with TBI for neuroprotection or restoration of maladaptive changes.Technologically, combination of imaging-based modelling or simultaneous brain signal monitoring with tDCS could result in greater individualized optimal targeting allowing a more favorable neuroplasticity after TBI. Moreover, a combination of task-oriented training using virtual reality with tDCS can be considered as a potent tele-rehabilitation tool in the home setting, increasing the dose of rehabilitation and neuromodulation, resulting in better motor recovery.This review summarizes the pathophysiology and possible neuroplastic changes in TBI, as well as provides the general concepts and current evidence with respect to the applicability of tDCS in motor recovery. Through its endeavors, it aims to provide insights on further successful development and clinical application of tDCS in motor rehabilitation after TBI.

Keywords: Electroencephalography; Functional near infrared spectroscopy; Neuronal plasticity; Recovery of function; Rehabilitation; Transcranial direct current stimulation; Traumatic brain injuries; Virtual reality.

Fig. 1

Pathophysiologic mechanisms of secondary injury after traumatic brain injury (Figure modified from reference [25])

Fig. 2

Strategy of noninvasive brain stimulation based on the interhemispheric inhibition model (Figure modified from reference [58])

Fig. 3

Schematic classification of personalized tDCS for motor recovery. Depending on electrode size, shape, and arrangement, tDCS can be broadly classified into a Conventional tDCS, b Customized Electrode tDCS, and c Distributed Array or High-Definition tDCS. Red color represents anodes and blue color represents cathodes

Fig. 4

Potential response analysis after personalized tDCS combined with EEG or fNIRS. (A) EEG power spectrum, hemodynamics, functional network, and stimulus responses can be monitored within or near stimulation electrode areas in personalized electrode tDCS. (B) Those parameters can be monitored in the whole brain areas in distributed array tDCS combined with EEG of fNIRS. Red color represents anodes and blue color represents cathodes. tDCS: transcranial direct current stimulation; EEG: electroencephalography; fNIRS: functional near infrared spectroscopoy

Fig. 5

Merged system with tDCS and virtual reality. Patient with TBI can use this system in the hospital setting with the supervision of clinican (a) and can continue to use it at their home with tele-monitored system (b)