The antinociceptive effect of transcranial electrostimulation with combined direct and alternating current in freely moving rats

Transcranial electrostimulation (TES) has been reported to elicit significant analgesia, allowing a substantial reduction of intraoperative opioids. Acceptance of TES into clinical practice is hampered by lack of controlled clinical trials and inconclusive animal data regarding the TES antinociceptive action. This inconclusive data may be explained, in part, by failure in rat experiments to simulate the variables used in humans when TES electrodes are positioned on the skin. In this study we validated the TES antinociceptive effect in a novel animal model of cutaneously administered TES, when the stimulating conditions mimic the ones used in clinical practice. The antinociceptive effect was assessed by measuring nociceptive thresholds in the tail-flick and hot-plate latency tests in awake, unrestrained male rats. Data were analyzed by analysis of variance and mixed-effects population modeling. The administration of TES at 2.25 mA produced an almost immediate, sustained, frequency-dependent (40-60 Hz) antinociceptive effect, reaching approximately 50% of the maximal possible value. We conclude that an antinociceptive effect of cutaneously administered TES can be demonstrated in the rat. Some characteristics of the effect suggest an important role of the sensory nerves of the rat's scalp in mediating the TES antinociceptive response. IMPLICATIONS: Transcranial electrostimulation produces a significant, frequency-dependent antinociceptive effect that may be mediated by cutaneous nerves of the scalp.     

A meta-analysis of the efficacy of anodal transcranial direct current stimulation for upper limb motor recovery in stroke survivors

Study DesignSystematic review and meta-analysis.IntroductionPrior reviews on the effects of anodal transcranial direct current stimulation (a-tDCS) have shown the effectiveness of a-tDCS on corticomotor excitability and motor function in healthy individuals but nonsignificant effect in subjects with stroke.PurposeTo summarize and evaluate the evidence for the efficacy of a-tDCS in the treatment of upper limb motor impairment after stroke.MethodsA meta-analysis of randomized controlled trials that compared a-tDCS with placebo and change from baseline.ResultsA pooled analysis showed a significant increase in scores in favor of a-tDCS (standard mean difference [SMD] = 0.40, 95% confidence interval [CI] = 0.10–0.70, p = 0.010, compared with baseline). A similar effect was observed between a-tDCS and sham (SMD = 0.49, 95% CI = 0.18–0.81, p = 0.005).ConclusionThis meta-analysis of eight randomized placebo-controlled trials provides further evidence that a-tDCS may benefit motor function of the paretic upper limb in patients suffering from chronic stroke.Level of EvidenceLevel 1a.     

Electrical stimulation of bone growth with direct current

Electrical stimulation of osteogenesis was studied in rabbit femora in: (A) a transcortical electric field with a cortex-depolarizing or hyperpolarizing orientation derived from an intramedullary electrode and a ring-shaped counter electrode encircling the femoral shaft; and (B) an electric field derived from an electrode located in the medullary canal and the counter electrode in the abdominal wall. Electrodes were made of platinum. A direct current of 20 microA was applied during six weeks. Contralateral femora with dummy electrodes served as controls. Results were analyzed by optical densitometry of roentgenograms and histomorphometry of histologic slides. Under the conditions of these experiments bone growth was not stimulated by applying a cortex-depolarizing electric field. Significant stimulation of bone growth was only observed at an intramedullary cathode, when the anode was placed at a distance.     

Treatment of nonunion with constant direct current.

Laboratory experiments show the following relationships between electricity and bone: (1) stressed bone exhibits electronegativity in areas of compression, (2) living, nonstressed bone exhibits electronegativity in areas of bone growth and healing, and (3) the application of low magnitude direct current to bone induces osteogenesis at the negative electrode or cathode. Based on the above principles, a clinical study was performed in which 10-20 microamperes of constant direct current was used in treating nonunion in 57 patients. The results suggest that specific electrical parameters are required for successful osteogenic stimulation in patients. When these electrical parameters are met, a successful healing rate of 70 per cent can be achieved in treating nonunion with direct current. As experience is gained with this new technique in the treatment of nonunion, the results should improve even further. Basic studies exploring the mechanism(s) whereby electricity induces osteogenesis are opening new vistas into our understanding of bone growth and repair. The extension of these basic studies has far-reaching clinical implications.     

Treatment of congenital pseudarthrosis of the tibia with direct current.

Bone possesses a bioelectric property that is important in maintaining its structural and architectural integrity. In vivo experiments demonstrate that bone formation can be accelerated by the application of direct current. We hypothesize that bone formation occurs through an electrochemical rather than an electromechanical effect. Two cases of congenital pseudarthrosis of the tibia treated by direct current stimulation are presented. A bone graft may be added to enhance bony union in conjunction with direct current. The implications of this work are that there is need for further fundamental studies including ultrastructural observations.     

Magnetic transcranial and electric direct stimulation of the facial motor cortex in dogs

Magnetic stimulation may allow noninvasive study of the entire course of the facial nerve. Our goal was to determine if evoked muscle action potentials can be obtained in facial musculature using electric direct cortical and noninvasive transcranial magnetic stimulation of the canine motor cortex. Thirty-four dogs were studied with electric direct cortical stimulation through a craniotomy and magnetic transcranial stimulation of the facial motor cortex. Facial nerve stimulation in the cerebellopontine angle allowed comparison to cortical responses. Latencies of 6.08 and 9.52 msec for orbicularis oculi and levator nasolabialis, respectively, were determined with magnetic transcranial stimulation, compared with 4.22 and 5.78 msec with electric direct cortical stimulation. In conclusion, magnetic stimulation of the facial motor cortex is possible in dogs, with longer central conduction times than with electric direct stimulation.     

Treatment of nonunion of the scaphoid by direct current

Seventy-one per cent (12 of 17) of scaphoid nonunions previously treated by other methods united when the semi-invasive technique of electrical stimulation was used. Patient acceptance of this electrode technique is high, and morbidity is lower than in patients treated by iliac bone grafting. The treatment of nonunion of the scaphoid by the semi-invasive electrical stimulation technique is a reasonable alternative to bone grafting and provides a salvage procedure when bone grafting or other therapeutic modalities have failed.     

Effect of weak direct current with silver electrodes on bacterial growth

The author studied the effect of weak direct current on bacterial growth in vitro and in vivo. In vitro, electric current was applied 20 or 100 micro A/cm2 of direct current using electrode of carbon, silver or platinum. Its inhibitory effect was observed on the growth curve of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa in the anode bath respectively. A silk thread that adsorbed Staphylococcus aureus was inserted into the intramedullary space of the tibia of Wistar rats to induce osteomyelitis. Silver electrodes were placed to apply 100 microA/cm2 of direct current for two weeks. The therapeutic effect was then evaluated in terms of X-ray findings, histological findings and changes in the viable count of Staphylococcus aureus in the intramedullary space of the tibia. It was found that application of electric current using a silver electrode was most effective for the inhibition of bacterial growth both in vivo and in vitro, and seemed to be clinically useful for treating osteomyelitis.     

Effects of direct current on renal function

Summary Electric current from an external source was introduced between electrodes operatively placed into the ureters and positioned in the renal pelves of 13 pigs. Urinary excretion via the cathodic kidney showed a marked increase. The renal plasma flow and glomerular filtration rate diminished with increasing voltage, but no significant difference was found between the cathodic and the anodic kidney. The fractional sodium excretion by the cathodic kidney was 80% higher, indicating that the electric current mainly affected tubular function. A possible clinical application for electric fields in the kidneys is discussed.     

Treatment of the neurogenic bladder with direct current on the spinal cord (Myelotron).

We carried out urodynamic examinations before and after galvanotherapy (Myelotron) of the spinal cord in 25 patients with upper and lower motor neuron lesions, mixed lesions and sensory lesions of the bladder. With the upper motor neuron lesions (neurogenic unhibited bladder, dyssynergia) there was a deterioration of the condition and therefore electrotherapy is contraindicated in this group of patients. With the lower motor neuron lesions and also the sensory lesions definite success was achieved with electrotherapy. Where there is a deficiency of impulses, it would appear to be compensated.     

Clinical experiences with low intensity direct current stimulation of bone growth.

Low intensity direct current stimulation of bone growth involves the continuous application of cathodic currents in the nanoampere range. The technique has been applied to 13 patients with a variety of non-unions and pseudarthroses with a success rate of 77 per cent. Preliminary data indicate that a range of total energy, from 0.6 to 2.5 Joules, is maximally effective. The technique has been combined with anodic control of local bacterial infection with promising results. Both the osteogenic stimulation and the bacterial suppression techniques as described in this paper, appear to be safe and effective.