A Retrospective Study on tDCS Treatment in Patients with Drug-Resistant Chronic Pain.

Background. Transcranial direct current stimulation (tDCS) of the primary motor cortex (M1) has an analgesic effect superior to a placebo in chronic pain. Some years ago, tDCS was implemented at the Hospital Nacional of Paraplegics (Toledo, Spain) to treat patients with pharmacological resistance to chronic pain. Objective. The main objectives of this study with tDCS were (1) to confirm the safety of one-year treatment; (2) to estimate the number of patients after one year in treatment; (3) to describe the effects of tDCS on the pain intensity during one-year treatment; and (4) to identify factors related to treatment success. Methods. This was a retrospective study conducted at the National Hospital for Paraplegics with 155 patients with pharmacologically resistant chronic pain. Anodal tDCS was applied over the M1 for 20 min at 1.5 mA for 10 treatment sessions from Monday to Friday (Induction phase), followed by 2-3 sessions per month (Maintenance phase). Pain intensity was assessed using a Visual Analogue Scale (VAS). Results. Anodal tDCS on M1 confirmed the reduction in the pain intensity. Moreover, 58% of outpatients completed one year of treatment. Only the VAS values obtained during the baseline influenced the response to treatment. Patients with a very high VAS at the baseline were more likely to not respond adequately to tDCS treatment. Conclusions. Anodal tDCS over M1 is an adequate therapy (safe and efficient) to treat drug-resistant chronic pain. Moreover, pain intensity at the start of treatment could be a predictor of patients' continuity with tDCS for at least one year.

Hand Motor Fatigability Induced by a Simple Isometric Task in Spinal Cord Injury.

This study aimed: (1) to evaluate the hand motor fatigability in people with spinal cord injury (SCI) and compare it with measurements obtained form an able-bodied population; (2) to compare the hand motor fatigability in people with tetraplegia and in people with paraplegia; and (3) to analyse if motor fatigability is different in people with SCI with and without clinical significant perceived fatigability. MATERIALS AND METHODS: 96 participants with SCI (40 cervical and 56 thoracolumbar) and 63 able-bodied controls performed a simple hand isometric task to assess motor fatigability. The Fatigue Severity Scale was used for perceived fatigability evaluation. RESULTS: The main results of this study can be summarized as follows: (1) the waning in muscle force (motor fatigability) during a fatiguing task is similar in controls and participants with SCI; (2) the motor fatigability is influenced by the maximal muscle force (measured at the beginning of the task); and (3) the perceived fatigability and the motor fatigability are largely independent in the individuals with SCI. CONCLUSION: Our findings suggest that the capability to maintain a prolonged effort is preserved in SCI, and this capacity depends on the residual maximal muscle force in people with SCI.

Effects of transcranial direct current stimulation on temperature and pain perception.

Transcranial direct current stimulation modifies cortical excitability and in consequence some cerebral functions. In the present study we aimed to elucidate whether tDCS could affect temperature and pain perceptions in healthy subjects testing different stimulation parameters. A total of 20 healthy subjects were studied by means of quantitative sensory testing. Two different experiments were performed. First, we studied the effects of 15 minutes 2 mA anodal transcranial direct current stimulation applied over left M1 and parietal cortex in two separated sessions. Then, we tested the effects of 5 minutes tDCS over M1 by means of a sham controlled design to optimize the possibility to study minimal effects of tDCS using different polarities (cathodal and anodal) and intensities (1 and 2 mA). 2 mA anodal tDCS, when applied for both 15 and 5 minutes over the motor cortex, increased cold perception threshold. Conversely, motor cortex cathodal tDCS modulated cold perception threshold only when 1 mA intensity was used. M1-tDCS can modify the temperature perception; these effects are polarity and intensity dependent. As stimulation intensity seems critical to determine the effects, we suggest that for clinical application strong anodal tDCS (>1 mA) or weak cathodal tDCS (<2 mA) should be used for pain control.

New Insights from Clinical Assessment of Upper Extremities in Cervical Traumatic Spinal Cord Injury.

Upper extremity function has a strong impact on the quality of life in cervical spinal cord-injured patients. Upper extremity function depends on many factors, such as muscle strength, level of lesion, and extension of the cord damage in its axial axis produced by the injury. These variables can be obtained by the International Standards for Neurological Classification of Spinal Cord Injury, which is the standard for the functional evaluation of traumatic spinal cord injury (SCI) patients. The aim of this study was to describe the relationship between upper limb muscle strength, level of injury, and axial damage with the functionality of upper limb measured using the Jebsen-Taylor Hand Function Test (JTHFT) and the 9 Hole Peg Test (9HPT) in cervical SCI. Twenty-nine patients were included in this study. Our results suggest that both the JTHFT and 9HPT can be similarly used to quantify functional impairment after cervical SCI. Moreover, our data suggest that the upper extremity motor score, JTHFT, and 9HPT strongly correlate with the American Spinal Injury Association (ASIA) impairment scale (graded from A to E), but not with the lesion level. Our findings can be of great importance for the clinician or researchers whose therapeutic interventions have as a main objective to improve upper limb functionality in patients with cervical SCI. We suggest that ASIA impairment scale, ASIA motor score, and functional tests (including JTHFT and/or 9HPT) could be used as outcome measures in cervical SCI clinical trials.