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

Simultaneous invasive and non-invasive recordings in humans: A novel Rosetta stone for deciphering brain activity

Simultaneous noninvasive and invasive electrophysiological recordings provide a unique opportunity to achieve a comprehensive understanding of human brain activity, much like a Rosetta stone for human neuroscience. In this review we focus on the increasingly-used powerful combination of intracranial electroencephalography (iEEG) with scalp electroencephalography (EEG) or magnetoencephalography (MEG). We first provide practical insight on how to achieve these technically challenging recordings. We then provide examples from clinical research on how simultaneous recordings are advancing our understanding of epilepsy. This is followed by the illustration of how human neuroscience and methodological advances could benefit from these simultaneous recordings. We conclude with a call for open data sharing and collaboration, while ensuring neuroethical approaches and argue that only with a true collaborative approach the promises of simultaneous recordings will be fulfilled.

Mandibular and chin electrodes as a supplemental recording for detection of epileptiform discharges in mesial temporal lobe epilepsy

Background

We previously demonstrated the usefulness of periorbital electrodes in supplemental recording to detect epileptiform discharges in patients with mesial temporal lobe epilepsy (MTLE). However, eye movement may disturb periorbital electrode recording. To overcome this, we developed mandibular (MA) and chin (CH) electrodes and examined whether these electrodes could detect hippocampal epileptiform discharges.

Methods

This study included a patient with MTLE, who underwent insertion of bilateral hippocampal depth electrodes and video-electroencephalographic (EEG) monitoring with simultaneous recordings of extra- and intracranial EEG as part of a presurgical evaluation. We examined 100 consecutive interictal epileptiform discharges (IEDs) recorded from the hippocampus and two ictal discharges. We compared these IEDs from intracranial electrodes with those from extracranial electrodes such as MA and CH electrodes in addition to F7/8 and A1/2 of international EEG 10-20 system, T1/2 of Silverman, and periorbital electrodes. We analyzed the number, rate of laterality concordance, and mean amplitude of IEDs detected in extracranial EEG monitoring and characteristics of IEDs on the MA and CH electrodes.

Results

The MA and CH electrodes had nearly the same detection rate of hippocampal IEDs from other extracranial electrodes without contamination by eye movement. Three IEDs, not detected by A1/2 and T1/2, could be detected using the MA and CH electrodes. In two ictal events, the MA and CH electrodes detected the ictal discharges from the hippocampal onset as well as other extracranial electrodes.

Conclusion

The MA and CH electrodes could detect hippocampal epileptiform discharges as well as A1/A2, T1/T2, and peri-orbital electrodes. These electrodes could serve as supplementary recording tools for detecting epileptiform discharges in MTLE.

[Sequential arterial spin labeling findings of status epilepticus showing generalized periodic discharges on EEG following acute infarction in the right occipital lobe]

In addition to electroencephalogram (EEG), arterial spin labeling (ASL) perfusion images with the dual postlabeling delay (PLD) method are useful for evaluating the hemodynamic state of status epilepticus (SE). A 72-year-old man suffered from an acute infarction in the right occipital lobe, resulting in SE with general periodic discharges on EEG with a higher amplitude on the right side. On ASL, blood flow was increased at a wide area of the right hemisphere centered on this infarct. With improvement of SE, sequential ASL with dual PLD method clearly demonstrated not only the reduction of the signal both in intensity and area but also the decrease of the blood flow velocity.

Good seizure outcome after focal resection surgery for super-refractory status epilepticus: Report of two cases

Background:

There is scarce evidence regarding focal resection surgery for super-refractory status epilepticus (SRSE), which is resistant to general anesthetic treatment over 24 h. We report two patients with SRSE, in whom good seizure outcomes were obtained following focal resection surgery.

Case Description:

Patient 1: A 58-year-old man who underwent left anterior temporal lobectomy with hippocampectomy at the age of 38 years after being diagnosed left medial temporal lobe epilepsy. After 19 years of surgery with no epileptic attacks, the patient developed SRSE. Electroencephalogram (EEG) demonstrated persistence of lateralized periodic discharges in the left frontotemporal region. On the 20^th day after SRSE onset, resection of the frontal lobe and temporal lobe posterior to the resection cavity was performed. Patient 2: A 62-year-old man underwent craniotomy for anaplastic astrocytoma in the left frontal lobe at the age of 34 years. Since the age of 60 years, he developed SRSE 3 times over 1 and 1/12 years. On EEG, repeated ictal discharges were observed at the medial part of the left frontal region during the three SRSEs. Corresponding to the ictal EEG findings, high signals on diffusion-weighted magnetic resonance images and focal hypermetabolism on fluorodeoxyglucose-positron emission tomography were observed around the supplementary motor area, medial to the resection cavity. Resection surgery of the area was performed during the interictal period.

Conclusion:

Good seizure outcome was obtained in the two cases which provide additional support for the recent concept of focal resection surgery as an indication for SRSE.

Lateralized Periodic Discharges During Remifentanil Infusion

Lateralized periodic discharges (LPDs) are a common electroencephalographic (EEG) pattern in the neurointensive care unit setting. LPDs are typically observed in association with acute structural lesions of the brain with different etiologies. There are no reports describing a link between the occurrence of LPDs and the administration of remifentanil. Remifentanil is a rapid-acting pure μ-opioid receptor agonist, which is indicated to provide analgesia and sedation in mechanically ventilated patients in intensive care units. We present a case of an 84-year-old man with neuroglycopenia who developed LPDs while sedated with remifentanil. We report, for the first time, a potential relationship between remifentanil and the induction of LPDs.