Transcranial magnetic stimulation for central pain

ANTITUMOR EFFECT OF ELECTROMAGNETIC FIELDS AND THEIR EFFECT ON PAIN IN EXPERIMENTAL AND CLINICAL ONCOLOGY

The review examined and analyzed scientific publications on the effect of electromagnetic fields (EMF) on various sys­tems of the human body and animals with tumors, as well as on pain in the experiment and the clinic. The theoretical foundations and practical results of the use of EMF in various modulations and modes in the goals and objectives of oncology, including how to optimize the process of anesthesia and correct the vital activity of the body's functional systems with a tumor, are consecrated. Information is given on possible physicochemical effects, features, and mecha­nisms of therapeutic influence at various levels of a living organism. The ability of electromagnetic waves to transfer in­formation both within a single biosystem and at the level of a whole living organism with a tumor is shown. Studies of combined action of EMF and chemotherapy were analyzed. It has been established that there are experimental prerequisites for using this factor in order to induce changes in the permeability of the membranes of tumor cells by in­creasing the internalization of chemotherapeutic agents and, thus, enhance the antitumor effect. The role of EMF in the induction of apoptosis in tumor cells is shown. It has been shown that chemotherapy together with electromagnetic fields induces apoptosis and has an inhibitory effect on DNA synthesis in osteosarcoma cells, breast cancer, colon cancer, melanoma and other tumors. The role of magnetic fields in order to enhance the analgesic effect was investigated. The analgesic effect is due to the cessation or weakening of nerve impulses from the painful focus due to the elimination of hypoxia, the improvement of microcirculation, and the reduction of edema, it has been shown. Transcranial magnetic therapy is used as an analgesic tool in onconurology. The therapeutic anti-pain effect is associated with the stimulation of the antinociceptive system, an increase in the synthesis of natural analgesics — endorphins with their subsequent release into the cerebrospinal fluid and blood. As it has already been shown, with the increase in the intensity of pain and its duration, all indicators of the quality of life and the results of treatment of the patient deteriorate, so the search for ways to improve the antitumor effectiveness of specialized treatment and eliminate the causes that prevent their im­plementation continue to be relevant and in demand.

c-Fos Expression After Chronic Electrical Stimulation of Sensorimotor Cortex in Rats

Objectives.  Motor cortex stimulation has been used as a treatment for intractable pain. However, the mechanisms underlying its effects remain unclear. In this study, neuroplasticity induced by chronic sensorimotor cortex stimulation was investigated experimentally on the basis of c-Fos expression. Materials and Methods.  The experimental animals employed were adult male Wistar rats. A quadripolar stimulation electrode was positioned over the sensorimotor cortex. We examined the neural activation in response to chronic stimulation using c-Fos immunopositivity. Results.  The results are as follows: 1) c-Fos was significantly expressed immediately after the stimulation compared with that in the control; 2) c-Fos expression became extensive over the various regions with an increase in stimulation duration; and 3) after two months of stimulation, c-Fos was expressed not only on the stimulation side, but also within the contralateral cerebral hemisphere. Conclusions.  Changes in c-Fos expression induced by long-term stimulation indicate the existence of a time-dependent neural plasticity.

Extradural cortical stimulation for central pain

Central pain results from a central nervous system injury and represents a challenge for the pain therapist. Human studies have shown that motor cortex stimulation (MCS), i.e. the placement of a stimulating plate on the dura overlying the motor cortex can relieve brain central pain. Studies suggest that MCS directly affects activity in the first and second order somatosensory areas, thalamic nuclei and also inhibits spinal primary afferents and spinothalamic tract neurons. The following factors have been found to predict analgesia by MCS: intact or almost intact corticospinal motor function, mild or negligible sensory loss, absence of thermal sensory threshold alteration within the painful area, positive response to the barbiturate and/or ketamine test, positive response to the propofol test, positive response to transcranial magnetic stimulation (TMS). The targeting of the cortical area is made by anatomical localization by computed tomography (CT), magnetic resonance imaging (MRI), neuronavigation, intraoperative neurophysiological recordings, functional MRI (fMRI), and intraoperative clinical assessment. We perform the procedure under local anaesthesia. We describe in detail our surgical technique and stimulation protocol. Furthermore, we review the most important studies with respect to their results, the observed side effects and complications. The future prospects and likely developments of MCS for central pain are also discussed.