Beamforming seizures from the temporal lobe

Background: Surgical treatment of drug-resistant temporal lobe epilepsy (TLE) depends on proper identification of the seizure onset zone (SOZ), and differentiation of mesial, temporolimbic seizure onsets from temporal neocortical seizure onsets. Non-invasive source imaging using electroencephalography (EEG) and magnetoencephalography (MEG) can provide accurate information on interictal spike localization; however, EEG and MEG have low sensitivity for epileptiform activity restricted to deep temporolimbic structures. Moreover, in mesial temporal lobe epilepsy (MTLE), interictal spikes frequently arise in neocortical foci distant from the SOZ, rendering interictal spike localization potentially misleading for presurgical planning. Methods: In this study, we used two different beamformer techniques applied to the MEG signal of ictal events acquired during EEG-MEG recordings in six patients with TLE (three neocortical, three MTLE). The ictal source localization results were compared to the patients' ground truth SOZ localizations determined from intracranial EEG and/or clinical, neuroimaging and postsurgical outcome evidence. Results: Beamformer analysis proved to be highly accurate in all cases and able to reliably identify focal seizure onsets localized to mesial, temporolimbic structures. In three patients, interictal spikes were either absent, too complex for inverse dipole modeling, or localized to anterolateral temporal neocortex distant to a mesial temporal SOZ. Conclusions: This report demonstrates the suitability of MEG beamformer analysis of ictal events in TLE, which can supersede or complement the traditional analysis of interictal spikes. The method outlined is applicable to any type of epileptiform event, greatly expanding the information value of MEG and broadening its utility for presurgical recording in epilepsy.

Download Full-text

Clinical seizure lateralization in mesial temporal lobe epilepsy: Differences between patients with unitemporal and bitemporal interictal spikes

Neurology ◽

10.1212/wnl.50.3.742 ◽

1998 ◽

Vol 50 (3) ◽

pp. 742-747 ◽

Cited By ~ 32

Author(s):

W. Serles ◽

E. Pataraia ◽

J. Bacher ◽

A. Olbrich ◽

S. Aull ◽

...

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Mesial Temporal Lobe Epilepsy ◽

Interictal Spikes ◽

Clinical Seizure ◽

Mesial Temporal Lobe

Download Full-text

EEG Signal Connectivity for Characterizing Interictal Activity in Patients With Mesial Temporal Lobe Epilepsy

Frontiers in Neurology ◽

10.3389/fneur.2021.673559 ◽

2021 ◽

Vol 12 ◽

Author(s):

Leonardo R. da Costa ◽

Brunno M. de Campos ◽

Marina K. M. Alvim ◽

Gabriela Castellano

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Betweenness Centrality ◽

Epileptiform Activity ◽

Mesial Temporal Lobe Epilepsy ◽

Eeg Signal ◽

Eeg Signals ◽

Graph Metrics ◽

Epileptiform Discharges ◽

Mesial Temporal Lobe

Over the last decade, several methods for analysis of epileptiform signals in electroencephalography (EEG) have been proposed. These methods mainly use EEG signal features in either the time or the frequency domain to separate regular, interictal, and ictal brain activity. The aim of this work was to evaluate the feasibility of using functional connectivity (FC) based feature extraction methods for the analysis of epileptiform discharges in EEG signals. These signals were obtained from EEG-fMRI sessions of 10 patients with mesial temporal lobe epilepsy (MTLE) with unilateral hippocampal atrophy. The connectivity functions investigated were motif synchronization, imaginary coherence, and magnitude squared coherence in the alpha, beta, and gamma bands of the EEG. EEG signals were sectioned into 1-s epochs and classified according to (using neurologist markers): activity far from interictal epileptiform discharges (IED), activity immediately before an IED and, finally, mid-IED activity. Connectivity matrices for each epoch for each FC function were built, and graph theory was used to obtain the following metrics: strength, cluster coefficient, betweenness centrality, eigenvector centrality (both local and global), and global efficiency. The statistical distributions of these metrics were compared among the three classes, using ANOVA, for each FC function. We found significant differences in all global (p < 0.001) and local (p < 0.00002) graph metrics of the far class compared with before and mid for motif synchronization on the beta band; local betweenness centrality also pointed to a degree of lateralization on the frontotemporal structures. This analysis demonstrates the potential of FC measures, computed using motif synchronization, for the characterization of epileptiform activity of MTLE patients. This methodology may be helpful in the analysis of EEG-fMRI data applied to epileptic foci localization. Nonetheless, the methods must be tested with a larger sample and with other epileptic phenotypes.

Download Full-text

Accuracy of ictal SPECT in mesial temporal lobe epilepsy with bilateral interictal spikes

Neurology ◽

10.1212/wnl.59.2.266 ◽

2002 ◽

Vol 59 (2) ◽

pp. 266-271 ◽

Cited By ~ 18

Author(s):

T. R. Velasco ◽

L. Wichert–Ana ◽

J. P. Leite ◽

D. Araújo ◽

V. C. Terra-Bustamante ◽

...

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Mesial Temporal Lobe Epilepsy ◽

Interictal Spikes ◽

Ictal Spect ◽

Mesial Temporal Lobe

Download Full-text

Intraoperative hippocampal electrocorticography to predict the extent of hippocampal resection in temporal lobe epilepsy surgery

Journal of Neurosurgery ◽

10.3171/jns.2000.93.1.0044 ◽

2000 ◽

Vol 93 (1) ◽

pp. 44-52 ◽

Cited By ~ 108

Author(s):

Guy M. McKhann ◽

Julie Schoenfeld-McNeill ◽

Donald E. Born ◽

Michael M. Haglund ◽

George A. Ojemann

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Seizure Control ◽

Epileptiform Activity ◽

Neuronal Loss ◽

Mesial Temporal Lobe Epilepsy ◽

Mesial Temporal Sclerosis ◽

Content Type ◽

Pathological Subtype ◽

Fine Print

Object. Among the variety of surgical procedures that are performed for the treatment of medically refractory mesial temporal lobe epilepsy (TLE), no consensus exists as to how much of the hippocampus should be removed. Whether all patients require a maximal hippocampal resection has not yet been determined.Methods. At the University of Washington, all TLE operations are performed in a tailored fashion, guided by electrocorticography (ECoG). The amount of hippocampal resection is determined intraoperatively by the extent of interictal epileptiform abnormalities on ECoG recorded from that structure, resulting in a hippocampal resection that is individualized for each patient. Using this approach, the authors prospectively observed 140 consecutive patients who underwent surgery for mesial TLE with pathological diagnoses of either mesial temporal sclerosis with neuronal loss (MTS group) or mild gliosis without neuronal loss (non-MTS group) to determine whether the extent of hippocampal resection correlates with outcome when a tailored approach is used. Additionally, the authors analyzed whether the presence of residual interictal epileptiform activity on ECoG following mesial temporal resection predicts poorer seizure control.With at least 18 months of clinical follow up, 67% of the 140 patients were seizure free or had only a single postoperative seizure. There was no correlation between the size of the hippocampal resection and seizure control in the group as a whole or when stratified by pathological subtype. Using an intraoperatively tailored strategy, individuals with a larger hippocampal resection (> 2.5 cm) were not more likely to have seizure-free outcomes than patients with smaller resections (p = 0.9). Additionally, both MTS and non-MTS patients, in whom postoperative ECoG detected residual epileptiform hippocampal (but not cortical or parahippocampal) interictal activity following surgical resection, had significantly worse seizure outcomes (p = 0.01 in the MTS group; p = 0.002 in the non-MTS group).Conclusions. Intraoperative hippocampal ECoG can predict how much hippocampus should be removed to maximize seizure-free outcome, allowing for sparing of possibly functionally important hippocampus.

Download Full-text

T10. Interictal spike rates are correlated with verbal memory in patients with mesial temporal lobe epilepsy

Clinical Neurophysiology ◽

10.1016/j.clinph.2018.04.011 ◽

2018 ◽

Vol 129 ◽

pp. e5

Author(s):

Tara Crowder Skarpaas ◽

David Loring ◽

Kim Meador ◽

Daniel Drane ◽

Martha Morrell

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Verbal Memory ◽

Mesial Temporal Lobe Epilepsy ◽

Interictal Spike ◽

Mesial Temporal Lobe

Download Full-text

The Prognostic Significance of Interictal Epileptiform Activity in Postoperative EEGs of Patients with Mesial Temporal Lobe Epilepsy

Clinical EEG and Neuroscience ◽

10.1177/155005940703800309 ◽

2007 ◽

Vol 38 (3) ◽

pp. 137-142 ◽

Cited By ~ 1

Author(s):

Svetlana Kipervasser ◽

Sari Nagar ◽

Vladimir Chistik ◽

Uri Kramer ◽

Itzhak Fried ◽

...

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Epileptiform Activity ◽

Prognostic Significance ◽

Mesial Temporal Lobe Epilepsy ◽

Seizure Recurrence ◽

Group 3 ◽

Mesial Temporal Lobe ◽

Eeg Recordings ◽

A Prospective Study

It has not been established whether electroencephalography (EEG) is a contributing factor in predicting the outcome of surgery for epilepsy. We conducted a prospective study on 26 patients (M/F 14/12, age: 33 ± 7.5 years, range 19–48) with mesial temporal lobe epilepsy (MTLE) who were followed for 2 years after surgery and who underwent routine EEG recordings 5.6 ± 3 months (range 3–12) postoperatively. Interictal epileptiform activity (IEA) on the EEG was compared in 17 seizure-free patients to 9 patients with recurrent seizures. The two groups were similar in gender, age, febrile convulsions, trauma, family history, seizure frequency prior to surgery, epilepsy duration and number of antiepileptic drugs. Following surgery, 17 study patients (65%) became seizure free; 9 (35%) had seizure recurrence. Postoperative EEG recordings showed IEA in 8/26 study patients (31%), 3 of whom were from the seizure-free group (3/17, 18%); 5 had seizure recurrence (5/9, 56%) (p=0.078). IEAs in postoperative EEGs were less frequently demonstrated in patients who were seizure free, but the presence of postoperative IEAs does not preclude successful surgical outcome.

Download Full-text