Ayumi Sakata

Correlation between scalp-recorded electroencephalographic and electrocorticographic activities during ictal period

OBJECTIVE To investigate the correlation between scalp-recorded electroencephalographic (EEG) and electrocorticographic (ECoG) activities during ictal periods. METHODS Simultaneous EEG and ECoG recordings with chronic subdural electrodes were performed in eight patients with partial epilepsy. RESULTS In two cases where the ictal ECoG discharges originated in deep brain structures such as the hippocampus and interhemispheric surface of the frontal lobe, ictal discharges could not be detected on EEG until they expanded to the cortex of convexity. In four cases, the ictal onset zones were located in the lateral convexity. When synchronous or near synchronous ictal ECoG discharges with amplitudes of 200-2000muV were recorded on more than 8-15cm(2) of cortex, corresponding discharges were recorded on EEG in these four cases. However, in a case of frontal lobe epilepsy, asynchronous ictal ECoG discharges were recorded on 10 electrodes of convexity but no ictal EEG activity was recorded. Furthermore, in two frontal lobe epilepsy cases, ictal EEG discharges did not always reflect the ictal ECoG spike, but occasionally reflected slow background ECoG activity around the ictal discharges. CONCLUSIONS Multiple factors such as the width of the cortical area involved, amplitude of ictal discharges and degree of synchronization of electrical potentials play important roles in the appearance of ictal EEG recordings, and the relationship between ictal EEG and ECoG is not straightforward.

Focal cortical dysplasia type IIa underlying epileptogenesis in patients with epilepsy associated with Sturge-Weber syndrome.

In patients with epilepsy associated with Sturge‐Weber syndrome (SWS), epileptogenesis has been suggested to be caused by chronic ischemia in cortical areas affected by leptomeningeal angiomatosis or by ischemia‐related cortical malformations. However, this has not been fully verified electrophysiologically. We herein present two cases of SWS with medically intractable epilepsy in which the epileptogenic area involved focal cortical dysplasia (FCD) type IIa near the region of leptomeningeal angiomatosis. In both cases, the ictal‐onset zones were identified by chronic subdural electrodes, and the presence of FCD type IIa was shown histopathologically. In SWS, especially in association with focal leptomeningeal angiomatosis, FCD may thus play a major role in epileptogenesis. FCD should therefore be demonstrated by the collective findings of perioperative neurophysiologic examination, anatomic and functional neuroimaging, and histopathologic examination.

Epileptogenicity of Supratentorial Medullary Venous Malformation

Summary:  Purpose: The purpose of this study was to evaluate the epileptogenicity of supratentorial medullary venous malformation (MVM). Special consideration was given to any associations with intracerebral hemorrhage with or without other vascular malformations, including cavernous angioma (CA).

Minimum norm estimates in MEG can delineate the onset of interictal epileptic discharges: A comparison with ECoG findings

The analysis of epileptic discharges in magnetoencephalography with minimum norm estimates (MNE) is expected to provide more precise localization of epileptic discharges compared with electroencephalographic estimations. However, the clinical feasibility of MNE remains unclear. In this study, we aimed to elucidate the onset and propagation patterns of interictal spikes using MNE. Seven patients with intractable epilepsy whose epileptogenicity was assumed to exist in the convexity of the cerebral cortex were studied. For MNE and electrocorticography (ECoG), we characterized the propagation patterns of interictal epileptic discharges according to the area in which they originated and where they extended; we then examined whether the propagation patterns observed in MNE were identified by ECoG. We also examined the relationship between the positions of spikes estimated by the equivalent current dipole (ECD) method and MNE. Among the seven patients, nine propagation patterns of epileptic discharges were observed by MNE, all of which were also identified by ECoG. In seven patterns, the epileptic activity propagated around the initial portion. However, in two patterns, the center of activities moved according to propagation with maintained activity of the initial portion. The locations of spikes identified by the ECD method were within the areas estimated by MNE when the epileptic activity propagated. However, the ECD method failed to detect onset activities identified by MNE in three of nine patterns. Thus, MNE is more useful as a means of presurgical evaluation for epilepsy than the ECD method because it can delineate the onset of epileptic activities as shown in ECoG.

Localization of epileptogenic zone in temporal lobe epilepsy by ictal scalp EEG

Our aim was to evaluate the ability to localize the epileptogenic zone in temporal lobe epilepsy (TLE) by ictal scalp electroencephalogram (EEG). Using simultaneous video recording, we analysed scalp EEG activity during ictal periods in 38 patients (30 patients with medial TLE (MTLE) and eight with lateral TLE (LTLE)). In 14 patients, intracranial ictal EEGs were recorded with depth electrodes, and simultaneous recordings of scalp and intracranial EEG were performed in 11 patients. Scalp EEG showed that, in all 30 patients with MTLE (71 of 72 seizures), an attenuation of background activity was observed before the appearance of ictal activity. Ictal discharges first appeared in the scalp EEG when the ictal discharges reached the lateral part of the temporal lobe on the intracranial EEG. While, in all eight patients with LTLE (25 of 25 seizures), the attenuation of background activity did not occur before the appearance of ictal activity. When the ictal discharges started in the lateral temporal lobe on intracranial EEG, ictal discharges appeared on the scalp. MTLE and LTLE could be diagnosed by the presence or absence of attenuation of background activity with clinical ictal signs before the appearance of ictal discharges.

Signal changes on magnetic resonance perfusion images with arterial spin labeling after carotid endarterectomy.

Background: Cerebral hyperperfusion after carotid endarterectomy (CEA) is defined as an increase in ipsilateral cerebral blood flow (CBF). Practically, however, prompt and precise assessment of cerebral hyperperfusion is difficult because of limitations in the methodology of CBF measurement during the perioperative period. Arterial spin labeling (ASL) is a completely noninvasive and repeatable magnetic resonance perfusion imaging technique that uses magnetically-labelled blood water as an endogenous tracer. To clarify the usefulness of ASL in the management of cerebral hyperperfusion, we investigated signal changes by ASL with a single 1.5-s post-labeling delay on visual inspection. Methods: Thirty-two consecutive patients who underwent CEA were enrolled in this retrospective study. Results: On postoperative day 1, 22 (68.8%) and 4 (12.5%) patients exhibited increased ASL signals bilaterally (Group A) and on the operated side (Group B), respectively. Follow-up ASL showed improvement in these findings. Six (18.8%) patients showed no change (Group C). There was no apparent correlation between ASL signals on postoperative day 1 and the preoperative hemodynamic state, including the cerebrovascular reserve (P = 0.2062). Three (9.4%) patients developed cerebral hyperperfusion syndrome (two in Group A and one in Group B). Coincidence in the localization of increased ASL signals and electroencephalographic abnormalities was noted in these patients. Conclusion: Visual analysis of ASL with a single post-labeling delay overestimates CBF and cannot identify patients at risk of cerebral hyperperfusion syndrome probably because of the strong effect of the shortened arterial transit time immediately after CEA. However, ASL may be used as for screening.

Various pathophysiological states of acute symptomatic seizures immediately following ischemic stroke, namely “onset seizures”, revealed by complementary use of periictal MRI and EEG

“Onset seizures” are acute symptomatic seizures occurring within 24 h after the onset of ischemic stroke, and their pathophysiological states are unknown. Electroencephalography is commonly used to diagnose epileptic activities; however, it is limited for use with acute stroke. Magnetic resonance imaging, including diffusion‐weighted imaging and perfusion imaging with arterial spin labeling, are applied mainly in an emergency. Ictal hyperperfusion on arterial spin labeling and cortical hyperintensity of cytotoxic edema on diffusion‐weighted imaging, peri‐ictally, can be obtained from an epileptically activated cortex.

Periodic Epileptiform Discharges in Children With Advanced Stages of Progressive Myoclonic Epilepsy

Huntington’s disease (HD) and dentatorubral-pallidoluysian atrophy (DRPLA) are monogenic forms of neurodegenerative disorders with autosomal dominant inheritance. Compared with adult-onset HD and DRPLA, children with these disorders are more severely affected and are known to manifest the devastating symptoms of progressive myoclonic epilepsy (PME) syndrome. In this report, we present a 6-year-old girl with HD from a family, and 2 siblings with DRPLA from another unrelated family. Serial neuroimaging and electroencephalography (EEG) studies showed that periodic epileptiform discharges and synchronized paroxysmal activity became prominent with their disease progression. Periodic complexes in EEG may emerge at advanced stages of childhood PME as a consequence of rapidly degenerating processes of their brain functions.

Clinical and histological characteristics of ictal onset zone in cases of intractable epilepsy associated with dysembryoplastic neuroepithelial tumor

Although the epileptogenic location of dysembryoplastic neuroepithelial tumors (DNTs) is controversial, it has recently been thought to be located within cortical dysplasia (CD) due to its frequent association with CD. Among the 84 resection surgeries for intractable epilepsy performed in our institution between January 2003 and April 2010, three patients had epileptogenic DNTs. In two cases, chronic subdural electrocorticography (ECoG) was performed, and the ictal onset zone was revealed to be in the cortex around the DNT. The ictal onset zone was resected along with the DNT, and good seizure outcome was achieved. Although histological examination of the ictal onset zone revealed mild gliosis, coexistence of CD was not noted. In the third case, the DNT was located in the left lateral temporal lobe and the intraoperative ECoG revealed frequent paroxysmal activity in the medial temporal lobe. Resection of the lateral temporal lobe involving the tumor did not result in good seizure control. The optimal surgical treatment of DNT is controversial. Some authors consider lesionectomy to be sufficient for good seizure control, whereas others advocate that additional resection of the epileptogenic zone beside the tumor improves outcome. Because the epileptogenic location of DNT varies among cases, it is important to identify its location by preoperative multimodal examinations, including chronic subdural ECoG recordings.

Erratum: Epileptogenicity of supratentorial medullary venous malformation (Epilepsia (2006) 47, (365-370))

FIG. 1. Case 2 (nonhemorrhagic group). A: A subtle enhanced linear lesion (white arrow) is noted in the right frontal lobe in a T1-weighted image with gadolinium enhancement. B: A lateral view of a right carotid angiogram shows a small medullary venous malformation (MVM; black arrow) draining into the superior sagittal sinus. C: Ictal EEG with averaged references demonstrates that ictal discharges begin in the left temporal region (T5, black arrow) and spread to the left hemisphere, although the MVM is located in the contralateral frontal lobe.