Epileptiform discharge propagation: Analyzing spikes from the onset to the peak

Mălîia, Mihai Dragoş; Meritam, Pirgit; Scherg, Michael; Fabricius, Martin; Rubboli, Guido; Mı̂ndruță, Ioana; Beniczky, Sándor

doi:10.1016/j.clinph.2015.12.021

Cited by 31 publications

(18 citation statements)

References 26 publications

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“…Interictal spikes were grouped based on common spike morphology and averaged to improve signal-to-noise ratio (SNR); a minimum of 10 spikes were averaged per analysis. Averaged interictal spikes were identified as propagating spikes using sequential 3D voltage maps and principal component analysis (PCA) 28 and were analysed at 50% of peak amplitude on the ascending portion; non-propagating spikes were analysed at peak to maximize SNR.…”

Section: Methodsmentioning

confidence: 99%

EEG source imaging concordance with intracranial EEG and epileptologist review in focal epilepsy

Cox

Danoun

Lundstrom

et al. 2021

Brain Communications

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EEG source imaging is becoming widely used for the evaluation of medically refractory focal epilepsy. The validity of EEG source imaging has been established in several studies comparing source imaging to the surgical resection cavity and subsequent seizure freedom. We present a cohort of 87 patients and compare EEG source imaging of both ictal and interictal scalp EEG to the seizure onset zone on intracranial EEG. Concordance of EEG source imaging with intracranial EEG was determined on a sublobar level and was quantified by measuring the distance between the source imaging result and the centroid of the active seizure onset zone electrodes. The EEG source imaging results of a subgroup of 26 patients with high density 76-channel EEG were compared with the localization of three experienced epileptologists. Of 87 patients, 95% had at least one analysis concordant with intracranial EEG and 74% had complete concordance. There was a higher rate of complete concordance in temporal lobe epilepsy compared to extratemporal (89.3 and 62.8%, respectively, P = 0.015). Of the total 282 analyses performed on this cohort, higher concordance was also seen in temporal discharges (95%) compared to extratemporal (77%) (P = 0.0012), but no difference was seen comparing high-density EEG with standard (32-channel) EEG. Subgroup analysis of ictal waveforms showed greater concordance for ictal spiking, compared with rhythmic activity, paroxysmal fast activity, or obscured onset. Median distances from the dipole and maximum distributed source to a centroid of seizure onset zone electrodes were 30.0 and 32.5 mm, respectively, and the median distances from dipole and maximum distributed source to nearest seizure onset zone electrode were 22.8 and 21.7, respectively. There were significantly shorter distances in ictal spiking. There were shorter distances in patients with Engel Class 1 outcome from surgical resection compared to patients with worse outcomes. For the subgroup of 26 high-density EEG patients, EEG source localization had a significantly higher concordance (92% versus 65%), sensitivity (57% versus 35%) and positive predictive value (60% versus 36%) compared with epileptologist localization. Our study demonstrates good concordance between ictal and interictal source imaging and intracranial EEG. Temporal lobe discharges have higher concordance rates than extratemporal discharges. Importantly, this study shows that source imaging has greater agreement with intracranial EEG than visual review alone, supporting its role in surgical planning.

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Section: Methodsmentioning

confidence: 99%

EEG source imaging concordance with intracranial EEG and epileptologist review in focal epilepsy

Cox

Danoun

Lundstrom

et al. 2021

Brain Communications

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“…The sublobar concordance rate may be higher than 73%, if up-to-date methods and procedures are applied. A recent EEG study showed that localizations of the spike onset can be in a different sublobar region than localizations of the peak in up to 40% [55]. Comparison to the reference standard of the decision of a multidisciplinary patient management conference ensures that the difference is not only caused by a lower SNR.…”

Section: Discussionmentioning

confidence: 99%

Interictal and Ictal MEG in presurgical evaluation for epilepsy surgery

Stefan

Rampp

2020

Acta Epileptologica

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Although presurgical evaluation of patients with pharamacoresistent focal epilepsies provides essential information for successful epilepsy surgery, there is still a need for further improvement. Developments of noninvasive electrophysiological recording and analysis techniques offer additional information based on interictal and ictal epileptic activities. In this review, we provide an overview on the application of ictal magnetoencephalography (MEG). The results of a literature research for published interictal/ictal MEG findings and experiences with own cases are demonstrated and discussed. Ictal MEG may provide added value in comparison to interictal recordings. The results may be more focal and closer to the invasively determined seizure onset zone. In some patients without clear interictal findings, ictal MEG could provide correct localization. Novel recording and analysis techniques facilitate ictal recordings. However, extended recording durations, movement and artifacts still represent practical limitations. Ictal MEG may provide added value regarding the localization of the seizure onset zone but depends on the selection of patients and the application of optimal analysis techniques.

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“…Do the voltage maps change during the epileptiform discharge? In approximately half of the cases [5], the voltage topography changes during the ascending slope of the epileptiform discharge. This is because the signal propagates from the onset cortical area to a neighbouring or another more distant area ‐ with different spatial orientation.…”

Section: Interpreting Voltage Mapsmentioning

confidence: 99%

Learn to interpret voltage maps: an atlas of topographies

Foged

Scherg²,

Fabricius

et al. 2022

Epileptic Disorders

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Describing the location of EEG abnormalities, such as interictal epileptiform discharges, is an important step in the interpretation of EEG recordings and has clinical relevance, as it is expected to point out the region of the brain generating these abnormal signals. Traditionally, the location is reported by specifying the area on the scalp where maximum negativity is located. However, this only reflects the correct localization in the brain when the cortical generator is located on the convexity (radial orientation). When the cortical generator is in the wall of a sulcus (tangential orientation), due to current flow (volume conduction), the maximum negativity is not over the generator, but at a distance from it. Voltage maps are widely available in most EEG reader software programs. Simple rules for reading voltage maps help to estimate the orientation and location of the source in the brain, avoiding false lateralization and false localization. In this seminar in epileptology, using a didactic approach, we explain how to read voltage maps and provide an atlas of voltage maps.

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Epileptiform discharge propagation: Analyzing spikes from the onset to the peak

Cited by 31 publications

References 26 publications

EEG source imaging concordance with intracranial EEG and epileptologist review in focal epilepsy

EEG source imaging concordance with intracranial EEG and epileptologist review in focal epilepsy

Interictal and Ictal MEG in presurgical evaluation for epilepsy surgery

Learn to interpret voltage maps: an atlas of topographies

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