Seizure Activity Across Scales From Neuronal Population Firing to Clonic Motor Semiology.

The correlation of clinical semiology with neuronal firing in human seizures has not been well described. Similarly, the neuronal firing patterns underlying high-frequency oscillations during seizures remain controversial. Using implanted subdural electrodes and a microelectrode array in a patient with focal status epilepticus, in which 40 habitual focal motor seizures and 101 subclinical seizures were captured, the authors analyzed the association of EEG, high-frequency oscillations, and multiunit activity to facial motor semiology. The development of ictal high-frequency oscillations in subdural electrodes overlying face motor cortex was temporally associated with clonic facial movements. In representative seizures selected for multiunit analysis, synchronization of neuronal firing in the adjacent microelectrode array aligned with clinical onset and was greater in clinical seizures compared with subclinical seizures. This report demonstrates the electrophysiologic signatures of focal seizures at the level of neuronal firing, high-frequency oscillations, and EEG as they organize from microscale to macroscale, with clinical correlation.