Transcranial direct current stimulation (tDCS) can effectively alleviate osteoarthritis (OA)-related knee pain, according to results from a double-blind, randomized and sham-controlled pilot clinical study presented at the American Pain Society’s 36th Annual Scientific Meeting in Pittsburgh, Pennsylvania. Upon session completion, participants in the tDCS group showed improved analgesia compared with patients in the sham tDCS group, as indicated by reported pain ratings (on a 0 to 100 numeric scale: 18.50 ± 3.60 vs 6.45 ± 2.26; mean difference 12.05 [P =.007]).
The knee joint is the most affected one in individuals with OA, the most prevalent type of arthritis and itself a major cause of disability in individuals aged ≥45 years. Although OA pain is commonly managed pharmacologically, these treatments (eg, tapentadol, corticosteroids) are often associated with adverse effects.2,3Neuromodulation of central pain pathways therefore represents an attractive alternative for the treatment of chronic pain, including knee OA-related pain. tDCS, a noninvasive technique increasingly used for the treatment of several conditions that include chronic pain, as well as motor and psychiatric disorders, exerts its effects by depolarizing (anodal tDCS) or hyperpolarizing (cathodal tDCS) cortical neurons.4,5
The current study aimed to evaluate the efficacy of tDCS in alleviating knee OA pain. Study participants (n = 40; mean age, 59 years; ages 50 to 70 years; 53% women) were randomly assigned to receive tDCS (2 mA) or sham tDCS for 20 minutes daily over a 5-day period. tDCS electrodes were placed on the primary motor cortex of the side contralateral to the painful knee (anode) and on the supraorbital region ipsilaterally (cathode).
Story from clinical pain adviser.
A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson’s disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer’s disease, tinnitus, depression, schizophrenia, and craving/addiction. The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10-24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode. It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform tDCS in a therapeutic setting. In addition, the easy management and low cost of tDCS devices allow at home use by the patient, but this might raise ethical and legal concerns with regard to potential misuse or overuse. We must be careful to avoid inappropriate applications of this technique by ensuring rigorous training of the professionals and education of the patients.
To systematically review the literature to date applying repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) for patients with fibromyalgia syndrome (FMS).
Electronic bibliography databases screened included PubMed, Ovid MEDLINE, PsychINFO, CINAHL, and Cochrane Library. The keyword “fibromyalgia” was combined with (“transcranial” and “stimulation”) or “TMS” or “tDCS” or “transcranial magnetic stimulation” or “transcranial direct current stimulation”.
Nine of 23 studies were included; brain stimulation sites comprised either the primary motor cortex (M1) or the dorsolateral prefrontal cortex (DLPFC). Five studies used rTMS (high-frequency-M1: 2, low-frequency-DLPFC: 2, high-frequency-DLPFC: 1), while 4 applied tDCS (anodal-M1: 1, anodal-M1/DLPFC: 3). Eight were double-blinded, randomized controlled trials. Most (80%) rTMS studies that measured pain reported significant decreases, while all (100%) tDCS studies with pain measures reported significant decreases. Greater longevity of significant pain reductions was observed for excitatory M1 rTMS/tDCS.
Studies involving excitatory rTMS/tDCS at M1 showed analogous pain reductions as well as considerably fewer side effects compared to FDA apaproved FMS pharmaceuticals. The most commonly reported side effects were mild, including transient headaches and scalp discomforts at the stimulation site. Yearly use of rTMS/tDCS regimens appears costly ($11,740 to 14,507/year); however, analyses to apapropriately weigh these costs against clinical and quality of life benefits for patients with FMS are lacking. Consequently, rTMS/tDCS should be considered when treating patients with FMS, particularly those who are unable to find adequate symptom relief with other therapies. Further work into optimal stimulation parameters and standardized outcome measures is needed to clarify associated efficacy and effectiveness.
Repetitive transcranial magnetic stimulation of the right secondary somatosensory motor cortex (S2) produces pain relief in patients with chronic neuropathic orofacial pain, an effect that was shown to be direct, and not a result of improvements in psychiatric or sleep disorder comorbidities. These findings were published in November in Medicine
The study participants had been diagnosed by a neurologist and an orofacial pain physician as follows: 7 had trigeminal neuropathic pain, 4 had atypical facial pain, and 5 had burning mouth syndrome. All patients displayed dysfunction of the trigeminal small- (and also large-, in some) fiber system, as well as a score ≥4 on the 0 to 10 numerical rating scale (NRS) for chronic daily neuropathic orofacial pain (daily average, 5.7; mean duration, 10.4 years).
Each study participant received 3 rTMS treatments (one of which was a placebo session), administered 4 weeks apart in a single-blind/within-subject manner. Stimulations (50 pulses at 90% of the resting motor threshold, every 10 s) targeted the facial area within the somatotopic representation of the primary sensorimotor cortex (S1/M1) and S2 in a random order.
Patients were assessed for psychiatric disorders based on the structured clinical interview for axis I disorders.3 Pain, mood, sleep and quality of life were assessed by study participants using the NRS to rate both pain and sleep and collected in study diaries for 4 weeks prior to and following treatment.
In addition, total hours of sleep, intensity, and interference of pain (measured using the Brief Pain Inventory),4 and sleep characteristics (assessed using the Basic Nordic Sleep Questionnaire),5 were all reported.
A more thorough assessment of sleep quality, measuring the 6 dimensions of sleep (ie, sleep disturbance , snoring, awakening with shortness of breath or headache, sleep adequacy, daytime somnolence, and quantity of sleep) was achieved through the Medical Outcomes Study (MOS) Sleep Measure, prior to and 1 month following each rTMS session.6
The authors found that neither sleep nor psychiatric disorders or medications (eg, opioids) had predictive value for rTMS treatment efficacy in study participants. The treatments had no detectable impact on either mood (assessed with the Beck Depression Inventory),7 or sleep quality.
Pain scores specific to neuropathic pain — but not to general pain — were reduced following S2 stimulation, as indicated by lower scores on the Neuropathic Pain Impact on Quality-of-Life questionnaire8 in treated vs sham-stimulated patients (P=.0031).
Six (38%) and 10 (63%) of the patients had a current or lifetime psychiatric disorder (depression or anxiety), respectively.
The authors concluded that “the present results show that the analgesic effect of rTMS given to the right S2 cortex as previously reported is most likely due to a direct action on specific top-down pain modulation networks rather than a result of an indirect action via improvement of comorbid psychiatric or sleep disturbances.”
They also added that “S2 stimulation had no effect on depressive symptoms, sleep diary measures, or the MOS sleep scale index scores, and that “comorbidities such as depression, anxiety disorders, and sleep problems did not predict the rTMS treatment outcome.”
Lindholm P, Lamusuo S, Taiminen T, et al. The analgesic effect of therapeutic rTMS is not mediated or predicted by comorbid psychiatric or sleep disorders. Medicine (Baltimore). 2016;95(44)
Lindholm P, Lamusuo S, Taiminen T, et al. Right secondary somatosensory cortex-a promising novel target for the treatment of drug-resistant neuropathic orofacial pain with repetitive transcranial magnetic stimulation. Pain. 2015;156(7):1276-1283
Results: We analyzed 9 articles with different methodologies (3 animals/6 humans) with a total of 174 stimulated individuals; 109 animals and 65 humans. In vivo and in vitro animal studies showed that direct current stimulation can successfully induce suppression of epileptiform activity without neurological injury and 4/6 (67%) clinical studies showed an effective decrease in epileptic seizures and 5/6 (83%) reduction of inter-ictal epileptiform activity. All patients tolerated tDCS well. Conclusions: tDCS trials have demonstrated preliminary safety and efficacy in animals and patients with epilepsy. Further larger studies are needed to define the best stimulation protocols and long-term follow-up.
Beck AT, Rial WY, Rickels K. Short form of depression inventory: crossvalidation. Psychol Rep. 1974;34:1184–1186