Simultaneous Electroencephalographic and Electocorticographic Recordings of Lateralized Periodic Discharges in Temporal Lobe Epilepsy

Abstract

Objective Lateralized periodic discharges (LPDs), which constitute an abnormal electroencephalographic (EEG) pattern, are most often observed in critically ill patients with acute pathological conditions, and are less frequently observed in chronic conditions such as focal epilepsies, including temporal lobe epilepsy (TLE). Here we aim to explore the pathophysiological mechanism of LPD in TLE. Methods We retrospectively selected 3 patients with drug-resistant TLE who simultaneously underwent EEG and electrocorticography (ECoG) and demonstrated LPDs. We analyzed the correlation between the EEG and ECoG findings. Results In patients 1 and 2, LPDs were recorded in the temporal region of the scalp during the interictal periods, when repeated spikes followed by slow waves (spike-and-wave complexes; SWs) and periodic discharges (PDs) with amplitudes of >600 to 800 µV appeared in the lateral temporal lobe over a cortical area of >10 cm2. In patient 3, when the ictal discharges persisted and were confined to the medial temporal lobe, repeated SWs were provoked on the lateral temporal lobe. When repeated SWs with amplitudes of >800 µV appeared in an area of the lateral temporal lobe of >10 cm2, the corresponding EEG discharges appeared on the temporal scalp. Conclusions LPDs in patients with TLE originate from repeated SWs and PDs of the lateral temporal lobe, which might represent a highly irritable state of the lateral temporal cortex during both interictal and ictal periods.

Reflection of the Ictal Electrocorticographic Discharges Confined to the Medial Temporal Lobe to the Scalp-Recorded Electroencephalogram

“…3 . 5 In the present case, ictal EEG discharges were hardly recognized when the amplitude of the ECoG discharges was less than 1500 μV, whereas it was clearly recognized as ictal EEG discharges when it was greater than 1500 to 2000 μV. These results support the previous findings.…”

“…This affects the amplitude and waveforms of the potentials, as a breach rhythm, recorded from the scalp electrode. 3,5,12 Although simultaneous scalp EEG and depth electrodes using stereotactic EEG techniques may minimize these problems, 13 this method could not evaluate the discharges from a wide area of the lateral temporal lobe very well. 5…”

“…3,5,12 Although simultaneous scalp EEG and depth electrodes using stereotactic EEG techniques may minimize these problems, 13 this method could not evaluate the discharges from a wide area of the lateral temporal lobe very well. 5…”

“…To demonstrate the interrelations between intracranial sources and scalp-recorded electroencephalography (EEG), several studies have performed simultaneous EEG recordings with intracranial recordings of electrocorticography (ECoG) using chronic subdural electrodes and/or depth electrodes. [1][2] Previous studies including ours [3][4][5][6][7] have shown that, in patients with temporal lobe epilepsy (TLE), ictal ECoG activities that originated from the medial temporal lobe could not be recorded on EEG, even if the amplitude of the discharge was as high as 1000 μV. In contrast, ictal discharges could be recorded on EEG after relatively low-amplitude ictal ECoG discharges spread to the lateral temporal lobe.…”

Lateralized Periodic Discharges During Remifentanil Infusion

“…Gray matter deafferentation was the first pathophysiological mechanism proposed, either as a result of white matter lesions 14 or due to acute and transient denervation in localized areas of the cortex. 15 LPDs have also been described in focal epilepsy 16 associated with altered cortical excitability. Alteration of cortical networks was also supported by a computational cortical model 17 which the reduction of excitatory afferents, from pyramidal glutamatergic cortical cells to interneurons, generated the characteristic periodic EEG pattern.…”