Analysis of Electrocorticography in Epileptic Patients With Responsive Neurostimulation Undergoing Scalp Electroencephalography Monitoring.

PURPOSE: To describe the relationship of electrocorticography events detected by a brain-responsive neurostimulation system (RNS) and their association with ictal and interictal activity detected on simultaneous scalp EEG. METHODS: We retrospectively identified patients with drug-resistant epilepsy implanted with RNS who subsequently underwent long-term scalp EEG monitoring. RNS detections were correlated to simultaneous activity recorded on scalp EEG to determine the characteristics of electrocorticography-stored long episodes associated with seizures or other findings on scalp EEG. RESULTS: Eleven patients were included with an average of 3.6 days of monitoring. Most RNS detections were of very brief duration (<10 seconds, 92.9%) and received one stimulation therapy (80.8%). A high proportion of long episodes (67.1%) were not identified as electrographic seizures on scalp EEG. Of those ictal-appearing (71.2%) long episodes, 68.2% had seizure correlates. Long episodes associated with seizures on scalp EEG had a longer median duration compared with those without (39.7 vs. 16.8 seconds, P < 0.002) and had broader spread pattern and were of higher amplitude on electrocorticography. Brief potentially ictal rhythmic discharges were the most common EEG findings associated with long episodes that did not have scalp EEG seizure correlates (100% for ictal- and 50% for non-ictal-appearing long episodes). CONCLUSIONS: Longer, broader spread and higher amplitude intracranial RNS detections are more likely to manifest as electrographic seizures on scalp EEG. Brief potentially ictal rhythmic discharges may serve as a scalp EEG biomarker of ictal intracranial episodes that are detected as long episodes by the RNS but not identified as electrographic seizures on scalp EEG.

Ictal head roll: a seizure semiology from the anterior prefrontal lobe.

Longstanding epilepsy can lead to modulation of cortical networks over time and unexpected seizure onset zones. Frontal lobe seizures, in particular, can have diverse semiologies and evolution patterns. We present a male patient with drug-resistant epilepsy secondary to severe traumatic brain injury who underwent bilateral stereo electroencephalography (SEEG) for surgical planning. SEEG localized an ictal circular head roll to the right anterior prefrontal region. This was followed by spread to the left orbitofrontal region and later the left amygdala and hippocampus, at which point a different semiology with behavioral arrest, lip smacking and oral automatisms began. This case, in which an ictal circular head roll was localized to the anterior prefrontal region, demonstrates the complexity of broad seizure networks that develop over time, leading to remote seizure spread.