5 research outputs found
Chronic iEEG recordings and interictal spike rate reveal multiscale temporal modulations in seizure states
Background and Objectives: Many biological processes are modulated by rhythms
on circadian and multidien timescales. In focal epilepsy, various seizure
features, such as spread and duration, can change from one seizure to the next
within the same patient. However, the specific timescales of this variability,
as well as the specific seizure characteristics that change over time, are
unclear.
Methods: Here, in a cross-sectional observational study, we analysed
within-patient seizure variability in 10 patients with chronic intracranial EEG
recordings (185-767 days of recording time, 57-452 analysed seizures/patient).
We characterised the seizure evolutions as sequences of a finite number of
patient-specific functional seizure network states (SNSs). We then compared SNS
occurrence and duration to (1) time since implantation and (2) patient-specific
circadian and multidien cycles in interictal spike rate.
Results: In most patients, the occurrence or duration of at least one SNS was
associated with the time since implantation. Some patients had one or more SNSs
that were associated with phases of circadian and/or multidien spike rate
cycles. A given SNS's occurrence and duration were usually not associated with
the same timescale.
Discussion: Our results suggest that different time-varying factors modulate
within-patient seizure evolutions over multiple timescales, with separate
processes modulating a SNS's occurrence and duration. These findings imply that
the development of time-adaptive treatments in epilepsy must account for
several separate properties of epileptic seizures, and similar principles
likely apply to other neurological conditions
Diminished circadian and ultradian rhythms in pathological brain tissue in human in vivo
Chronobiological rhythms, such as the circadian rhythm, have long been linked
to neurological disorders, but it is currently unknown how pathological
processes affect the expression of biological rhythms in the brain. Here, we
use the unique opportunity of long-term, continuous intracranially recorded EEG
from 38 patients (totalling 6338 hours) to delineate circadian and ultradian
rhythms in different brain regions. We show that functional circadian and
ultradian rhythms are diminished in pathological tissue, independent of
regional variations. We further demonstrate that these diminished rhythms are
persistent in time, regardless of load or occurrence of pathological events.
These findings provide the first evidence that brain pathology is functionally
associated with persistently diminished chronobiological rhythms in vivo in
humans, independent of regional variations or pathological events. Future work
interacting with, and restoring, these modulatory chronobiological rhythms may
allow for novel therapies
A library of quantitative markers of seizure severity
OBJECTIVE: Understanding fluctuations in seizure severity within individuals is important for determining treatment outcomes and responses to therapy, as well as assessing novel treatments for epilepsy. Current methods for grading seizure severity rely on qualitative interpretations from patients and clinicians. Quantitative measures of seizure severity would complement existing approaches, for electroencephalographic (EEG) monitoring, outcome monitoring, and seizure prediction. Therefore, we developed a library of quantitative EEG markers that assess the spread and intensity of abnormal electrical activity during and after seizures. METHODS: We analysed intracranial EEG (iEEG) recordings of 1009 seizures from 63 patients. For each seizure we computed 16 markers of seizure severity that capture the signal magnitude, spread, duration, and post-ictal suppression of seizures. RESULTS: Quantitative EEG markers of seizure severity distinguished focal vs. subclinical seizures across patients. In individual patients 53% had a moderate to large difference (ranksum r>0.3, p<0.05) between focal and subclinical seizures in three or more markers. Circadian and longer-term changes in severity were found for the majority of patients. SIGNIFICANCE: We demonstrate the feasibility of using quantitative iEEG markers to measure seizure severity. Our quantitative markers distinguish between seizure types and are therefore sensitive to established qualitative differences in seizure severity. Our results also suggest that seizure severity is modulated over different timescales. We envisage that our proposed seizure severity library will be expanded and updated in collaboration with the epilepsy research community to include more measures and modalities. © 2023 International League Against Epilepsy
Frailty Models with Application in Lymphoma data
Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Εφαρμοσμένες Μαθηματικές Επιστήμες
Temporal stability of intracranial EEG abnormality maps for localizing epileptogenic tissue
OBJECTIVE: Identifying abnormalities in interictal intracranial EEG, by comparing patient data to a normative map, has shown promise for the localization of epileptogenic tissue and prediction of outcome. The approach typically uses short interictal segments of around one minute. However, the temporal stability of findings has not been established. METHODS: Here, we generated a normative map of iEEG in non-pathological brain tissue from 249 patients. We computed regional band power abnormalities in a separate cohort of 39 patients for the duration of their monitoring period (0.92-8.62 days of iEEG data, mean 4.58 days per patient, over 4,800 hours recording). To assess the localizing value of band power abnormality, we computed Drs - a measure of how different the surgically resected and spared tissue were in terms of band power abnormalities - over time. RESULTS: In each patient, the Drs value was relatively consistent over time. The median Drs of the entire recording period separated seizure free (ILAE = 1) and not seizure free (ILAE > 1) patients well (AUC = 0.69). This effect was similar interictally (AUC = 0.69) and peri-ictally (AUC = 0.71). SIGNIFICANCE: Our results suggest that band power abnormality Drs , as a predictor of outcomes from epilepsy surgery, is a relatively robust metric over time. These findings add further support for abnormality mapping of neurophysiology data during presurgical evaluation