transcranial Direct Current Stimulation (tDCS) for the treatment and investigation of Phantom Limb Pain (PLP)

Effect of transcranial direct current stimulation on supernumerary phantom limb pain in spinal cord injured patient: A case report

BACKGROUND

Supernumerary phantom limb (SPL) sensation is the experience of additional limbs, either single or a pair of limbs. Unique to traumatic spinal cord injuries, we report effect of transcranial direct current stimulation (tDCS) on SPL pain in a patient with cervical cord injury.

CASE SUMMARY

The subject was a 57-year-old man who was diagnosed with complete spinal cord injury (C6/C5, motor level; C5/C5, sensory level; AIS-A) approximately three months ago. After a period of 2 wk, we administered anodal tDCS over the motor cortex for 15 minutes at an intensity of 1.5 mA. Following that treatment, the patient experienced a decrease of SPL pain intensity and frequency, which lasted for 1 week after the end of treatment.

CONCLUSION

Targeting the motor cortex through neuromodulation appears to be a promising option for the management of SPL pain.

Performance in myoelectric pattern recognition improves with transcranial direct current stimulation

Sensorimotor impairments, resulting from conditions like stroke and amputations, can profoundly impact an individual's functional abilities and overall quality of life. Assistive and rehabilitation devices such as prostheses, exo-skeletons, and serious gaming in virtual environments can help to restore some degree of function and alleviate pain after sensorimotor impairments. Myoelectric pattern recognition (MPR) has gained popularity in the past decades as it provides superior control over said devices, and therefore efforts to facilitate and improve performance in MPR can result in better rehabilitation outcomes. One possibility to enhance MPR is to employ transcranial direct current stimulation (tDCS) to facilitate motor learning. Twelve healthy able-bodied individuals participated in this crossover study to determine the effect of tDCS on MPR performance. Baseline training was followed by two sessions of either sham or anodal tDCS using the dominant and non-dominant arms. Assignments were randomized, and the MPR task consisted of 11 different hand/wrist movements, including rest or no movement. Surface electrodes were used to record EMG and the MPR open-source platform, BioPatRec, was used for decoding motor volition in real-time. The motion test was used to evaluate performance. We hypothesized that using anodal tDCS to increase the excitability of the primary motor cortex associated with non-dominant side in able-bodied individuals, will improve motor learning and thus MPR performance. Overall, we found that tDCS enhanced MPR performance, particularly in the non-dominant side. We were able to reject the null hypothesis and improvements in the motion test's completion rate during tDCS (28% change, p-value: 0.023) indicate its potential as an adjunctive tool to enhance MPR and motor learning. tDCS appears promising as a tool to enhance the learning phase of using assistive devices using MPR, such as myoelectric prostheses.

Time since onset might be of essence: A recommendation to assess the effects of combination of non-pharmacological neuromodulatory approaches at early stage since symptoms onset

In the past decade researchers began to assess the potential beneficial effects of non-invasive brain stimulation (NIBS) combined with a behavioral task as a treatment approach for various medical conditions. Transcranial direct current stimulation (tDCS) applied to the motor cortex combined with another treatment approach has been assessed as analgesic treatment in neuropathic and non-neuropathic pain conditions, and was found to exert only modest pain relief. Our group results show that combined tDCS and mirror therapy dramatically reduced acute phantom limb pain intensity with long-lasting effects, potentially preventing pain chronification. A review of the scientific literature indicates that our approach differs from that of others: We applied the intervention at the acute stage of the disease, whereas other studies applied the intervention in patients whose disease had already been established. We suggest that the timing of administration of the combined intervention is critical. Unlike in patients with chronic painful condition, in which the maladaptive plasticity associated with pain chronification and chronicity is well-consolidated, early treatment at the acute pain stage may be more successful in counterbalancing the not-yet consolidated maladaptive plasticity. We encourage the research community to test our hypothesis, both in the treatment of pain, and beyond.

Mindful SensoriMotor Therapy combined with brain modulation for the treatment of pain in individuals with disarticulation or nerve injuries: a single-arm clinical trial

INTRODUCTION

Neuropathic pain is a complex and demanding medical condition that is often difficult to treat. Regardless of the cause, the impairment, lesion or damage to the nervous system can lead to neuropathic pain, such as phantom limb pain (PLP). No treatment has been found widely effective for PLP, but plasticity-guided therapies have shown the least severe side effects in comparison to pharmacological or surgical interventions. Phantom motor execution (PME) is a plasticity-guided intervention that has shown promising results in alleviating PLP. The potential mechanism underlying the effectiveness of PME can be explained by the Stochastic Entanglement hypothesis for neurogenesis of neuropathic pain resulting from sensorimotor impairment. We have built on this hypothesis to investigate the efficacy of enhancing PME interventions by using phantom motor imagery to facilitate execution and with the addition of sensory training. We refer to this new treatment concept as Mindful SensoriMotor Therapy (MiSMT). In this study, we further complement MiSMT with non-invasive brain modulation, specifically transcranial direct current stimulation (tDCS), for the treatment of neuropathic pain in patients with disarticulation or peripheral nerve injury.

METHODS AND ANALYSIS

This single-arm clinical trial investigates the efficacy of MiSMT and tDCS as a treatment of neuropathic pain resulting from highly impaired extremity or peripheral nerve injury in eight participants. The study consists of 12 sessions of MiSMT with anodal tDCS in the motor cortex, pretreatment and post-treatment assessments, and follow-up sessions (up to 6 months). The primary outcome is the change in pain intensity as measured by the Pain Rating Index between the first and last treatment sessions.

ETHICS AND DISSEMINATION

The study is performed under the approval of the governing ethical committee in Sweden (approval number 2020-07157) and in accordance with the Declaration of Helsinki.

TRIAL REGISTRATION NUMBER

NCT04897425.

Applications of open-source software ROAST in clinical studies: A review

Background:

Transcranial electrical stimulation (TES) is broadly investigated as a therapeutic technique for a wide range of neurological disorders. The electric fields induced by TES in the brain can be estimated by computational models. A realistic and volumetric approach to simulate TES (ROAST) has been recently released as an open-source software package and has been widely used in TES research and its clinical applications. Rigor and reproducibility of TES studies have recently become a concern, especially in the context of computational modeling.

Methods:

Here we reviewed 94 clinical TES studies that leveraged ROAST for computational modeling. When reviewing each study, we pay attention to details related to the rigor and reproducibility as defined by the locations of stimulation electrodes and the dose of stimulating current. Specifically, we compared across studies the electrode montages, stimulated brain areas, achieved electric field strength, and the relations between modeled electric field and clinical outcomes.

Results:

We found that over 1800 individual heads have been modeled by ROAST for more than 30 different clinical applications. Similar electric field intensities were found to be reproducible by ROAST across different studies at the same brain area under same or similar stimulation montages.

Conclusion:

This article reviews the use cases of ROAST and provides an overview of how ROAST has been leveraged to enhance the rigor and reproducibility of TES research and its applications.