46 As with other types of environmentally provoked seizures, e.g. those triggered by hypoglycemia, there is no evidence that a single provoked seizure can or will
trigger epilepsy. The only common adverse effect of TMS is headache, which is reported by about 1 in 10 subjects. This is attributed to the TMS coil being pressed against subjects’ heads for an extended time. The TMS-induced headaches are usually mild and respond to usual headache treatments such as acetaminophen. Lastly, depending on where TMS is applied, and its intensity, suprathreshold application to the motor cortex can activate the facial, trigeminal, or auditory nerves to cause discomfort. As with MRI, people undergoing TMS are usually offered earplugs to minimize exposure Inhibitors,research,lifescience,medical to the noises generated by the TMS coils. RECENT TECHNOLOGICAL ADVANCES AND RECOMMENDATION FOR FUTURE RESEARCH Over the years TMS pulse generators have not changed significantly, but new coil designs and cooling units allow more TMS pulses to be administered at higher frequencies and more focally. Cooled coils prevent coils from overheating Inhibitors,research,lifescience,medical after a long series of pulses. Innovative coil configurations provide greater focality and deeper penetration.
Inhibitors,research,lifescience,medical Brainsway’s H-coil allows deeper penetration of TMS pulses. It obtained EU approval to treat major depressive disorder in 2008, bipolar depression in 2009, schizophrenia in 2010, and post-traumatic stress disorder in 2011. In January 2013, Brainsway won US and Canadian approval to market its Deep TMS device for drug-resistant depression.47 Home-based rTMS systems are currently in development.48 Another significant development, introduced Inhibitors,research,lifescience,medical more than a decade ago, is “neuronavigated” TMS. Several companies developed “CX-4945 in vivo frameless stereotactic” systems (Figure 1) that use infrared cameras to register position and orientation of the TMS coil relative to the subject’s head, and integrate individual cortical topography from each person’s head MRI, to guide placement of Inhibitors,research,lifescience,medical the TMS coil. This informs the TMS administrator
about the actual location of the desired brain target in that person and also enables placing the coil at precisely the same spot during different TMS sessions. Computer modeling shows that MRI-navigated TMS reduces variability in induced current compared to hand-held TMS, and more precisely and reproducibly locates motor cortex targets in human patients.49–51 Nexstim’s Navigated Brain Stimulation system won FDA approval Cell press for presurgical mapping of cortical function in 2010. Importantly, almost all studies of rTMS for pain used hand-held coils, meaning that the location of stimulation likely varied slightly during successive sessions, as illustrated in Figure 2. Additional study is required to determine if MRI-navigated TMS improves outcomes. Figure 1 The MRI-navigated Nexstim Interface. Figure 2 MRI-guided Neuronavigation Allows rTMS to Target the Same Cortex More Precisely and Reproducibly.