
Noninvasive Brain Stimulation in the Treatment of Acquired Brain Injury
Noninvasive brain stimulation techniques have been shown to be safe and effective in treating the cognitive, physical, and emotional consequences of acquired brain injury.
According to the Brain Injury Association of America, an
ABI can result in multiple and complex changes in several domains, including physical/somatic, cognitive, emotional, and behavioral.5 Physical or somatic consequences can include
A substantial number of individuals with ABI require intensive rehabilitation to recover. Neurorehabilitation programs affect change in function by promoting plasticity through activity-based neurostimulation.7 Neuronal circuits are modified by experience and learning. Research has shown that experience-dependent learning can change neural circuity at multiple levels of the central nervous system, including synapses, cortical maps, and larger neural networks.8,9 While the effectiveness of neurorehabilitation is well documented, there is wide variability of therapeutic interventions, inconsistencies in frequency and duration of treatment, and
Additionally, some treatments for the consequences of ABI—particularly pharmacological treatment for mood disorders, cognitive dysfunction, and motor/movement disorders—can cause adverse effects.11 Noninvasive brain stimulation has been shown to be a safe, effective treatment following ABI, allowing for greater control of neuromodulation with minimal adverse effects. Two methods of noninvasive brain stimulation, transcranial direct current stimulation (tDCS) and
Repetitive Transcranial Magnetic Stimulation
rTMS is a neuromodulator tool used to regulate neural activity through the use of rapidly alternating magnetic fields. A magnetic pulse passes through the skull and induces activity in a targeted (ie, focal) cortical region. Pulses can be delivered repetitively to produce long-term changes in neural activity. Cortical excitability can be upregulated through the application of high-frequency stimulation (>5 Hz), or downregulated with low-frequency stimulation (~1 Hz).14
Hummel and colleagues noted an interhemispheric imbalance in patients with brain injury and noninvasive brain stimulation can reduce the imbalance.15 High frequency stimulation of an affected hemisphere increases cortical excitability, whereas low frequency stimulation of an unaffected hemisphere decreases cortical excitability. rTMS has been shown to be safe and risks of adverse effects are low when established guidelines are followed. Common adverse effects of rTMS include headache and minor scalp irritation following therapy, but these tend to be transient. Though rarely reported in the literature, there is an increased risk for seizure activity in persons with brain injury, requiring additional monitoring or management via strict criteria for inclusion in treatment.16
Transcranial Direct Current Stimulation
tDCS is another noninvasive neuromodulator tool that uses low amplitude direct current, usually 1 to 2 milliamps, to alter cortical excitability. tDCS regulates cortical excitability by altering neuronal resting membrane potentials, increasing the likelihood of depolarization (increasing cortical excitability) or hyperpolarization (decreasing cortical excitability). An anode and cathode electrodes are placed over the head. Anodal tDCS increases underlying cortical excitability, while cathodal tDCS decreases underlying cortical excitability.17 As with rTMS, the administration of tDCS is safe and effective. Adverse effects, such as moderate fatigue, mild headache, nausea, and itching at the area of stimulation, are infrequent and transient. According to Nitsche and colleagues, the risk for
Use and Effectiveness in Rehabilitation Following Acquired Brain Injury
Neuromodular techniques, such as rTMS and tDCS can be administered as monotherapy, but may produce better clinical outcomes when combined with other therapeutic interventions, such as cognitive rehabilitation, physical therapy, and
Zaninotto and colleagues reviewed the literature on the effects of tDCS on recovery following TBI. While results were mixed, the authors reported that in most studies, tDCS improved responsiveness in patients with disorders of consciousness; improved cognitive function, particularly when tDCS was paired with cognitive rehabilitation; and improved motor recovery when paired with physical therapy. Anodal stimulation and electrode placement were consistent in all studies (ie, left dorsolateral prefrontal cortex). However, large variability was noted in stimulation parameters, the number of tDCS sessions, and pairing with additional therapies.These methodological differences may account for mixed results.
Lee and Kim investigated the use of low frequency rTMS to treat depression and cognitive deficits in patients with TBI using a randomized controlled design.13 Participants were randomly assigned to an experimental or control group. Measurements of depressive symptoms and
rTMS has also been used to treat language deficits (improvements noted in naming accuracy, word repetition), visuospatial neglect (improvements noted in line bisection and clock drawing task), and executive functioning in individuals with TBI or stroke.20-22
Concluding Thoughts
Noninvasive brain stimulation techniques, such as rTMS and tDCS have been shown to be safe and effective in treating the cognitive, physical, and emotional consequences following acquired brain injury. rTMS and tDCS allow for controlled and targeted neuromodulation, and when combined with other therapeutic approaches—such as physical therapy, occupational therapy, speech/language therapy, and psychotherapy—may produce superior outcomes. Noninvasive brain stimulation techniques may be a suitable alternative to treatments that can cause deleterious adverse effects following ABI.
Dr Seale is the regional director of clinical services at the Centre for Neuro Skills, which operates post-acute brain injury rehabilitation programs in California and Texas. He is licensed in Texas as a chemical dependency counselor and psychological associate with independent practice. He also holds a clinical appointment at the University of Texas Medical Branch (UTMB) in Galveston in the Department of Rehabilitation Sciences.
References
1. What is the difference between acquired brain injury and traumatic brain injury? Brain Injury Association of America. Accessed November 10, 2022.
2. Definition of acquired brain injury. Toronto Acquired Brain Injury Network. March 31, 2005. Accessed November 10, 2022.
3. Report to Congress on Traumatic Brain Injury in the United States: Epidemiology and Rehabilitation. Centers for Disease Control and Prevention; National Center for Injury Prevention and Control; Division of Unintentional Injury Prevention. 2015. Accessed November 10, 2022.
4. Stroke. Centers for Disease Control and Prevention. 2021. Accessed November 10, 2022.
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16. Kletzel SL, Aaronson AL, Guernon A, et al.
17. Nitsche MA, Liebetanz D, Lang N, et al.
18. Nitsche MA, Cohen LG, Wassermann EM, et al.
19. Zaninotto AL, El-Hagrassy MM, Green JR, et al.
20. Barwood CH, Murdoch BE, Whelan BM, et al.
21. Lim JY, Kang EK, Paik NJ.
22. Hara T, Abo M, Sasaki N, et al.
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