What is a contraindication for using transcranial magnetic stimulation?

A contraindication for using transcranial magnetic stimulation (TMS) includes the presence of a cardiac pacemaker. This is due to the potential for TMS to induce electrical currents that can interfere with the normal function of the pacemaker, possibly leading to malfunction or abnormal heart rhythms. The magnetic fields generated during TMS could disrupt the pacing function, posing a serious risk to patient safety.

In the context of the other options, while patient obesity can complicate TMS administration, it is not a strict contraindication. Multiple sclerosis (MS) is not typically contraindicated for TMS; in fact, some studies suggest that TMS may be beneficial for certain symptoms associated with MS. Similarly, transverse myelitis, a condition affecting the spinal cord, may also not strictly contraindicate TMS, although caution is warranted depending on individual patient circumstances. Therefore, the presence of a cardiac pacemaker is a clearly defined contraindication due to the risks it poses to cardiac safety.