Seizure incidence during single- and paired-pulse transcranial magnetic stimulation (TMS) in individuals with epilepsy

Objective: We reviewed published data and our own data to determine a quantitative incidence of seizure in subjects with epilepsy undergoing single- and paired-pulse transcranial magnetic stimulation (spTMS and ppTMS) and to explore conditions that may increase this risk. Methods: A PubMed literature search was performed, and articles from this search were reviewed. Subjects from our institution also were included. Results: The crude risk of a TMS-associated seizure ranges from 0.0 to 2.8% for spTMS and 0.0–3.6% for ppTMS. Medically intractable epilepsy and lowering antiepileptic drugs were associated with increased incidence. There was significant center-to-center variability that could not be explained by differences in patient population or by differences in reported stimulation parameters. In all cases, seizures were similar to each subject's typical seizure and without long-term adverse outcome. In most cases, doubt was expressed in the original reports as to whether the seizures were induced by TMS or merely coincidental. Conclusions: The incidence of seizure in a subject with epilepsy during spTMS and ppTMS appears to be small and not associated with long-term adverse outcome. The incidence is higher under the specific conditions mentioned above. Significance: These findings may enable researchers to more accurately inform subjects of seizure risk during TMS.