Thus, electromyography equipment is usually interfaced with the TMS equipment and used to set the TMS pulse intensity to a sub-threshold value

that is a fixed percentage (e.g. 80%–90%) of the patient’s resting motor threshold (RMT). Typically this procedure is repeated before each TMS session. The RMT is defined as the minimum stimulation intensity that elicits a motor response to 5 of 10 TMS pulses. The RMT depends on various factors, including the integrity of motor pathways and the Inhibitors,research,lifescience,medical tonic level of excitability in the muscle, as well as individual scalp-to-cortex distance and effect of pharmacological treatment.17 After assessing the RMT and setting the intensity, rTMS is applied in bursts of stimuli (“trains”) using a specific frequency and inter-train interval. The number of pulses delivered is usually between 500 and 2,500, and frequencies between 5 Hz and 20 Hz are used. Coil design Inhibitors,research,lifescience,medical and orientation are also important. Early coils were simple circles. The later “figure-of-eight” coil uses two circular coils to induce a stronger and more focal magnetic field at their intersection. Other newer designs include the tilted double-coil

and the H-coil, which uses multiple loops to penetrate up to 8 cm or increase focality. Since the orientation Inhibitors,research,lifescience,medical of the magnetic field determines which neurons are affected, specific coil orientations are preferred when stimulating different brain regions. REVIEW OF THE STUDIES OF rTMS OF THE MOTOR CORTEX FOR CHRONIC PAIN Studies involving one single application of rTMS to the motor cortex have provided proof of concept for efficacy

against pain. Some involve experimental Inhibitors,research,lifescience,medical induction of brief pains in healthy volunteers (reviewed in Mylius et al.18) or in patients with chronic pain. These studies were used to compare efficacy Inhibitors,research,lifescience,medical of different stimulation sites, specifically the primary and secondary motor selleck chemical cortices, dorsolateral prefrontal cortex, the primary and secondary somatosensory cortices, and the supplementary and premotor areas.18 As with epidural stimulation, stimulating the primary motor cortex generally provided the best pain relief. In contrast, depression is best treated by applying rTMS to the dorsolateral prefrontal cortex—additional evidence of different anatomical Brefeldin_A substrates for NP and depression. The fact that motor but not sensory cortex stimulation relieves pain is not yet understood. Although TMS only directly affects the superficial cortex since the currents rapidly dissipate,19 the action potentials triggered propagate to influence distributed neural networks. Effects of motor cortex stimulation on chronic pain are thought to involve M1 projections to pain-modulating structures; perhaps among them are the medial thalamus, anterior cingulate/orbitofrontal cortices, and the periaqueductal gray matter (PAG).