Central-Positive Complexes: A Novel Characterization of Ictal Markers Induced during Electroconvulsive Therapy

Objectives Electroencephalography (EEG) allows monitoring of generalized seizures induced during electroconvulsive therapy (ECT). Scalp EEG recordings show different phases of electroencephalographic ictal activity during ECT seizures, documenting a pattern of seizures that may vary within and across individuals. In this case series, we used 64-electrode high-density EEG recording to detect topographic electroencephalographic changes not typically evident with conventional limited montages commonly used during ECT. Methods The EEG recordings were acquired from 5 participants (24 ECT sessions) during index courses for treatment-resistant depression. Using previously proposed staging criteria, the ictal EEG and simultaneously acquired video were interpreted by an expert reviewer blinded to study treatment parameters. Results The EEG recordings of all seizures showed generalized, high-amplitude, central-positive complexes (CPCs), which emerged at the beginning of phase III (polyspike and slow wave activity), with median duration of 47 seconds (interquartile range, 77 seconds), ranging from 14 to 203 seconds. Although individuals showed variability in frequency and amplitude of CPCs, CPCs typically evolved from 4.0 to 1.5 Hz in frequency and decreased in amplitude as the seizure progressed. Elaborating on previously described phases of ECT-induced electrographic seizures, we describe variability in morphology at seizure termination. Initiation of CPCs typically corresponded with clonic movements, but often terminated after motor signs ceased. Conclusions Generalized, high-amplitude, CPCs during ECT are a previously uncharacterized ictal waveform during ECT, which may have important scientific and clinical value. These complexes offer a specific marker for correlating clinical outcomes in ECT and greater understanding of generalized tonic-clonic seizures.