Noninvasive brain stimulation to modulate neuroplasticity in traumatic brain injury

Glutamate and GABA imbalance following traumatic brain injury

Traumatic brain injury (TBI) leads to multiple short- and long-term changes in neuronal circuits that ultimately conclude with an imbalance of cortical excitation and inhibition. Changes in neurotransmitter concentrations, receptor populations, and specific cell survival are important contributing factors. Many of these changes occur gradually, which may explain the vulnerability of the brain to multiple mild impacts, alterations in neuroplasticity, and delays in the presentation of posttraumatic epilepsy. In this review, we provide an overview of normal glutamate and GABA homeostasis and describe acute, subacute, and chronic changes that follow injury. We conclude by highlighting opportunities for therapeutic interventions in this paradigm.

Transcranial magnetic stimulation facilitates neurorehabilitation after pediatric traumatic brain injury

Traumatic brain injury (TBI) is the leading cause of death and disability among children in the United States. Affected children will often suffer from emotional, cognitive and neurological impairments throughout life. In the controlled cortical impact (CCI) animal model of pediatric TBI (postnatal day 16-17) it was demonstrated that injury results in abnormal neuronal hypoactivity in the non-injured primary somatosensory cortex (S1). It materializes that reshaping the abnormal post-injury neuronal activity may provide a suitable strategy to augment rehabilitation. We tested whether high-frequency, non-invasive transcranial magnetic stimulation (TMS) delivered twice a week over a four-week period can rescue the neuronal activity and improve the long-term functional neurophysiological and behavioral outcome in the pediatric CCI model. The results show that TBI rats subjected to TMS therapy showed significant increases in the evoked-fMRI cortical responses (189%), evoked synaptic activity (46%), evoked neuronal firing (200%) and increases expression of cellular markers of neuroplasticity in the non-injured S1 compared to TBI rats that did not receive therapy. Notably, these rats showed less hyperactivity in behavioral tests. These results implicate TMS as a promising approach for reversing the adverse neuronal mechanisms activated post-TBI. Importantly, this intervention could readily be translated to human studies.

Noninvasive brain stimulation for persistent postconcussion symptoms in mild traumatic brain injury

Mild traumatic brain injury (mTBI) is typically followed by various postconcussive symptoms (PCS), including headache, depression, and cognitive deficits. In 15-25% of cases, PCS persists beyond the usual 3-month recovery period, interfering with activities of daily living and responding poorly to pharmacotherapy. We tested the safety, tolerability, and efficacy of repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (DLPFC) for alleviating PCS. Fifteen eligible patients with mTBI and PCS > 3 months postinjury consented to 20 sessions of rTMS (20 × 5-sec trains; 10 Hz at 110% threshold), with clinical and functional magnetic resonance imaging (fMRI) assessments before and after intervention and clinical assessment at 3-month follow-up. Primary outcomes were tolerability, safety, and efficacy, as measured with the PCS Scale. Secondary outcomes included the Cognitive Symptoms Questionnaire, neuropsychological test performance, and working memory task-associated activity as assessed with fMRI. Twelve patients completed all sessions. Three withdrew because of worsening symptoms or for an unrelated event. Stimulation intensity was increased gradually across sessions, and all subjects tolerated the protocol by the sixth session. Commonly reported side effects among completers were increased headache (n = 3) and greater sleep disturbance (n = 3). Participants also reported positive outcomes such as less sleep disturbance (n = 3), and better mental focus (n = 3). On average, PCS scores declined by 14.6 points (p = 0.009) and fMRI task-related activation peaks in the DLPFC increased after rTMS. rTMS is safe, tolerated by most patients with mTBI, and associated with both a reduction in severity of PCS and an increase in task-related activations in DLPFC. Assessment of this intervention in a randomized, control trial is warranted.

Transcranial direct current stimulation combined with integrative speech therapy in a child with cerebral palsy: A case report

The aim of this study was to describe the results of the first case combining integrative speech therapy with anodal transcranial direct current stimulation (tDCS) over Broca's area in a child with cerebral palsy. The ABFW phonology test was used to analyze speech based on the Percentage of Correct Consonants (PCC) and Percentage of Correct Consonants - Revised (PCC-R). After treatment, increases were found in both PCC (Imitation: 53.63%-78.10%; Nomination: 53.19%-70.21%) and PPC-R (Imitation: 64.54%-83.63%; Nomination: 61.70%-77.65%). Moreover, reductions occurred in distortions, substitutions and improvement was found in oral performance, especially tongue mobility (AMIOFE-mobility before = 4 after = 7). The child demonstrated a clinically important improvement in speech fluency as shown in results of imitation number of correct consonants and phonemes acquire. Based on these promising findings, continuing research in this field should be conducted with controlled clinical trials.

Effects of repeated anodal tDCS coupled with cognitive training for patients with severe traumatic brain injury: a pilot randomized controlled trial

OBJECTIVE

To determine whether cumulative anodal transcranial direct current stimulation (A-tDCS) of the left dorsolateral prefrontal cortex (DLPFC) could enhance rehabilitation of memory and attention in patients with traumatic brain injury (TBI).

SETTING

Inpatient and outpatient neurorehabilitation unit.

PARTICIPANTS

Twenty-three adult patients, 4- to 92- months post severe TBI.

DESIGN

Participants were randomly allocated to 2 groups. The experimental group received A-tDCS (10 minutes; 1 mA; in the DLPFC), followed by rehabilitative cognitive training, daily for 15 days. Controls received A-tDCS for 25 seconds (sham condition) with the same rehabilitation.

MAIN MEASURES

Battery of memory and attention tests, which included visual and auditory modalities. Participants were tested twice before beginning rehabilitation (to control for spontaneous recovery), after rehabilitation completion, and 4 months later.

RESULTS

Tests scores in both groups were similar at 3 weeks before and immediately before treatment. After treatment, the experimental group exhibited larger effect sizes in 6 of 8 cognitive outcome measures, but they were not significantly different from controls. At follow-up, differences remained insignificant.

CONCLUSION

In contrast to previous studies, our study did not provide sufficient evidence to support the efficacy of repeated A-tDCS for enhancing rehabilitation of memory and attention in patients after severe TBI.

Clinical utility of brain stimulation modalities following traumatic brain injury: current evidence

Traumatic brain injury (TBI) remains the main cause of disability and a major public health problem worldwide. This review focuses on the neurophysiology of TBI, and the rationale and current state of evidence of clinical application of brain stimulation to promote TBI recovery, particularly on consciousness, cognitive function, motor impairments, and psychiatric conditions. We discuss the mechanisms of different brain stimulation techniques including major noninvasive and invasive stimulations. Thus far, most noninvasive brain stimulation interventions have been nontargeted and focused on the chronic phase of recovery after TBI. In the acute stages, there is limited available evidence of the efficacy and safety of brain stimulation to improve functional outcomes. Comparing the studies across different techniques, transcranial direct current stimulation is the intervention that currently has the higher number of properly designed clinical trials, though total number is still small. We recognize the need for larger studies with target neuroplasticity modulation to fully explore the benefits of brain stimulation to effect TBI recovery during different stages of recovery.

Novel insights into the rehabilitation of memory post acquired brain injury: a systematic review

Objective: Acquired Brain Injury (ABI) frequently results in memory impairment causing significant disabilities in daily life and is therefore a critical target for cognitive rehabilitation. Current understanding of brain plasticity has led to novel insights in remediation-oriented approaches for the rehabilitation of memory deficits. We will describe 3 of these approaches that have emerged in the last decade: Virtual Reality (VR) training, Computer-Based Cognitive Retraining (CBCR) and Non-Invasive Brain Stimulation (NBS) and evaluate its effectiveness.

Methods: A systematic literature search was completed in regard to studies evaluating interventions aiming to improve the memory function after ABI. Information concerning study content and reported effectiveness were extracted. Quality of the studies and methods were evaluated.

Results: A total of 786 studies were identified, 15 studies met the inclusion criteria. Three of those studies represent the VR technique, 7 studies represent CBCR and 5 studies NBS. All 3 studies found a significant improvement of the memory function after VR-based training, however these studies are considered preliminary. All 7 studies have shown that CBCR can be effective in improving memory function in patients suffering from ABI. Four studies of the 5 did not find significant improvement of the memory function after the use of NBS in ABI patients.

Conclusion: On the basis of this review, CBCR is considered the most promising novel approach of the last decade because of the positive results in improving memory function post ABI. The number of studies representing VR were limited and the methodological quality low, therefore the results should be considered preliminary. The studies representing NBS did not detect evidence for the use of NBS in improving memory function.

Systematic review and meta-analysis of noninvasive cranial nerve neuromodulation for nervous system disorders

OBJECTIVE

To systematically review the medical literature and comprehensively summarize clinical research done on rehabilitation with a novel portable and noninvasive electrical stimulation device called the cranial nerve noninvasive neuromodulator in patients suffering from nervous system disorders.

DATA SOURCES

PubMed, MEDLINE, and Cochrane Database of Systematic Reviews from 1966 to March 2013.

STUDY SELECTION

Studies were included if they recruited adult patients with peripheral and central nervous system disorders, were treated with the cranial nerve noninvasive neuromodulator device, and were assessed with objective measures of function.

DATA EXTRACTION

After title and abstract screening of potential articles, full texts were independently reviewed to identify articles that met inclusion criteria.

DATA SYNTHESIS

The search identified 12 publications: 5 were critically reviewed, and of these 5, 2 were combined in a meta-analysis. There were no randomized controlled studies identified, and the meta-analysis was based on pre-post studies. Most of the patients were individuals with a chronic balance dysfunction. The pooled results demonstrated significant improvements in the dynamic gait index postintervention with a mean difference of 3.45 (95% confidence interval, 1.75-5.15; P<.001), Activities-specific Balance Confidence scale with a mean difference of 16.65 (95% confidence interval, 7.65-25.47; P<.001), and Dizziness Handicap Inventory with improvements of -26.07 (95% confidence interval, -35.78 to -16.35; P<.001). Included studies suffered from small sample sizes, lack of randomization, absence of blinding, use of referral populations, and variability in treatment schedules and follow-up rates.

CONCLUSIONS

Given these limitations, the results of the meta-analysis must be interpreted cautiously. Further investigation using rigorous randomized controlled trials is needed to evaluate this promising rehabilitation tool for nervous system disorders.

Technique and considerations in the use of 4x1 ring high-definition transcranial direct current stimulation (HD-tDCS)

High-definition transcranial direct current stimulation (HD-tDCS) has recently been developed as a noninvasive brain stimulation approach that increases the accuracy of current delivery to the brain by using arrays of smaller "high-definition" electrodes, instead of the larger pad-electrodes of conventional tDCS. Targeting is achieved by energizing electrodes placed in predetermined configurations. One of these is the 4x1-ring configuration. In this approach, a center ring electrode (anode or cathode) overlying the target cortical region is surrounded by four return electrodes, which help circumscribe the area of stimulation. Delivery of 4x1-ring HD-tDCS is capable of inducing significant neurophysiological and clinical effects in both healthy subjects and patients. Furthermore, its tolerability is supported by studies using intensities as high as 2.0 milliamperes for up to twenty minutes. Even though 4x1 HD-tDCS is simple to perform, correct electrode positioning is important in order to accurately stimulate target cortical regions and exert its neuromodulatory effects. The use of electrodes and hardware that have specifically been tested for HD-tDCS is critical for safety and tolerability. Given that most published studies on 4x1 HD-tDCS have targeted the primary motor cortex (M1), particularly for pain-related outcomes, the purpose of this article is to systematically describe its use for M1 stimulation, as well as the considerations to be taken for safe and effective stimulation. However, the methods outlined here can be adapted for other HD-tDCS configurations and cortical targets.

NON-INVASIVE BRAIN STIMULATION IN CHILDREN: APPLICATIONS AND FUTURE DIRECTIONS

Transcranial magnetic stimulation (TMS) is a neurostimulation and neuromodulation technique that has provided over two decades of data in focal, non-invasive brain stimulation based on the principles of electromagnetic induction. Its minimal risk, excellent tolerability and increasingly sophisticated ability to interrogate neurophysiology and plasticity make it an enviable technology for use in pediatric research with future extension into therapeutic trials. While adult trials show promise in using TMS as a novel, non-invasive, non-pharmacologic diagnostic and therapeutic tool in a variety of nervous system disorders, its use in children is only just emerging. TMS represents an exciting advancement to better understand and improve outcomes from disorders of the developing brain.