The safety of transcranial magnetic stimulation reconsidered: evidence regarding cognitive and other cerebral effects

The potential of transcranial magnetic stimulation (TMS) to cause undesired or unexpected effects on cognition and other cerebral functions has received only limited study, although extensive clinical use has suggested that obvious problems are unlikely. Evidence so far accumulated suggests that exposure to TMS in the expected clinical situations will have no persistent effects on the electroencephalogram (EEG) or on cognitive function, although transient effects may occur. The absence of increases in either prolactin or adrenocorticotropic hormone (ACTH) in subjects undergoing TMS indicates that seizure-like events do not routinely occur, although recent evidence suggests that TMS may cause seizures or enhance the occurrence of epileptiform abnormalities in circumstances of heightened susceptibility. Despite these observations, treated seizure patients are unlikely to experience seizures with TMS. The technique is generally safe, but not entirely free from unwanted effects, and further study to define those effects is warranted.