Transcranial Magnetic Stimulation (TMS) modulates epileptiform discharges in patients with Frontal Lobe epilepsy: a Preliminary EEG-TMS Study

BACKGROUND TMS is being increasingly used as a noninvasive brain stimulation technique for the therapeutic management of partial epilepsies. However, the acute effects of TMS on epileptiform discharges (EDs, i.e. interictal epileptiform activity and subclinical electrographic seizure patterns) remain unexplored. OBJECTIVE To investigate whether TMS can modulate EDs in partial epilepsy. METHODS In Experiment Set 1, the safety of the TMS protocol was investigated in 10 well-controlled by anti-epileptic drugs (AEDs) epileptic patients. In Experiment Set 2, the effects of TMS on EDs were studied in three subjects with intractable frontal lobe epilepsies, characterized by particularly frequent EDs. TMS was applied over the electrographic focus with a circular and a figure of eight coil while recording EEG with a 60-channel TMS-compatible EEG system. The effectiveness of TMS in aborting EDs was investigated using survival analysis and brain connectivity analysis. RESULTS The TMS protocol was well-tolerated. TMS was an effective method to abort EDs even when adjusting for its latency with respect to ED onset (CMH test, p < 0.0001). While the effective brain connectivity around the epileptic focus increased significantly during EDs (p < 0.01), with TMS administration the increase was not statistically significant. CONCLUSION TMS can modulate EDs in patients with epileptogenic foci in the cortical convexity and is associated with reversal of ED-induced changes in brain connectivity.