Nadja Birk - Academia.edu (original) (raw)

Papers by Nadja Birk

Annals of clinical and translational neurology, Nov 21, 2019

Objective: Many patients with epilepsy have both focal and bilateral tonic-clonic seizures (BTCSs... more Objective: Many patients with epilepsy have both focal and bilateral tonic-clonic seizures (BTCSs), but it is largely unclear why ictal activity spreads only sometimes. Previous work indicates that interictal high-frequency oscillations (HFOs), traditionally subdivided into ripples (80-250 Hz) and fast ripples (250-500 Hz), are a promising biomarker of epileptogenicity. We aimed to investigate whether HFOs correlate with the emergence of seizure activity and whether they differ between focal seizures (FSs) with impaired awareness and BTCSs. Methods: We retrospectively analyzed 15 FSs and 13 BTCSs from seven patients with mesial temporal lobe epilepsy, each of them with at least one BTCS and at least one FS. Representative intervals of intracranial electroencephalography from the seizure onset zone (SOZ) and remote non-SOZ areas were selected to compare pre-ictal, complex focal, tonic-clonic, and postictal periods. Ripples and fast ripples were visually identified and their density, that is, percentage of time occupied by the respective events, computed. Results: Ripple and fast ripple densities increased inside the SOZ after seizure onset (P < 0.01) and in remote areas after progression to BTCSs (P < 0.01). Postictal SOZ ripple density dropped below pre-ictal levels (P < 0.001). Prior to onset of bilateral tonic-clonic movements, ripple density inside the SOZ is higher in BTCSs than in FSs (P < 0.05). Interpretation: Ripples and fast ripples correlate with onset and spread of ictal activity. Abundant ripples inside the SOZ may reflect the activation of specific neuronal networks related to imminent spread of seizure activity.

Frontiers in Human Neuroscience, 2021

High-frequency oscillations (HFOs, ripples 80–250 Hz, fast ripples 250–500 Hz) are biomarkers of ... more High-frequency oscillations (HFOs, ripples 80–250 Hz, fast ripples 250–500 Hz) are biomarkers of epileptic tissue. They are most commonly observed over areas generating seizures and increase in occurrence during the ictal compared to the interictal period. It has been hypothesized that their rate correlates with the severity of epilepsy and seizure in affected individuals. In the present study, it was aimed to investigate whether the HFO count mirrors the observed behavioral seizure severity using a kainate rat model for temporal lobe epilepsy. Seizures were selected during the chronic epilepsy phase of this model and classified by behavioral severity according to the Racine scale. Seizures with Racine scale 5&6 were considered generalized and severe. HFOs were marked in 24 seizures during a preictal, ictal, and postictal EEG segment. The duration covered by the HFO during these different segments was analyzed and compared between mild and severe seizures. HFOs were significantly in...

Annals of Clinical and Translational Neurology, 2019

ObjectiveMany patients with epilepsy have both focal and bilateral tonic‐clonic seizures (BTCSs),... more ObjectiveMany patients with epilepsy have both focal and bilateral tonic‐clonic seizures (BTCSs), but it is largely unclear why ictal activity spreads only sometimes. Previous work indicates that interictal high‐frequency oscillations (HFOs), traditionally subdivided into ripples (80–250 Hz) and fast ripples (250–500 Hz), are a promising biomarker of epileptogenicity. We aimed to investigate whether HFOs correlate with the emergence of seizure activity and whether they differ between focal seizures (FSs) with impaired awareness and BTCSs.MethodsWe retrospectively analyzed 15 FSs and 13 BTCSs from seven patients with mesial temporal lobe epilepsy, each of them with at least one BTCS and at least one FS. Representative intervals of intracranial electroencephalography from the seizure onset zone (SOZ) and remote non‐SOZ areas were selected to compare pre‐ictal, complex focal, tonic‐clonic, and postictal periods. Ripples and fast ripples were visually identified and their density, that ...

Hochfrequenzoszillationen (HFO) im Bereich von 80-500 Hz gelten als vielversprechende Marker von ... more Hochfrequenzoszillationen (HFO) im Bereich von 80-500 Hz gelten als vielversprechende Marker von Epileptogenität. Ihre Anwendung finden sie vor allem im Bereich der prächirurgischen Epilepsiediagnostik zur Detektion zu resezierender Gehirnareale. Da die pathophysiologischen Mechanismen von HFO in der Anfallsgenese und -terminierung jedoch bislang nicht ausreichend erklärt sind, ist auch ihre Aussagekraft eingeschränkt. Bislang gibt es keine Informationen zu HFO und ihrem Vorkommen bei verschiedenen Anfallsstärken. In der vorliegenden Studie wurden HFO zunächst im Kainat-Rattenmodell und anschließend bei Patienten mit mesialer Temporallappenepilepsie analysiert. Es wurden 24 Anfälle von 2 Ratten in die Studie eingeschlossen. Nach visueller Analyse der EEG-Abschnitte mit einem Hochpassfilter wurden die Raten von HFO für einen jeweils 30-sekündigen präiktalen, iktalen und postiktalen Abschnitt berechnet und anschließend nach den verschiedenen Anfallsstärken aufgeteilt. Ripples (80-250 ...

Annals of clinical and translational neurology, Nov 21, 2019

Objective: Many patients with epilepsy have both focal and bilateral tonic-clonic seizures (BTCSs... more Objective: Many patients with epilepsy have both focal and bilateral tonic-clonic seizures (BTCSs), but it is largely unclear why ictal activity spreads only sometimes. Previous work indicates that interictal high-frequency oscillations (HFOs), traditionally subdivided into ripples (80-250 Hz) and fast ripples (250-500 Hz), are a promising biomarker of epileptogenicity. We aimed to investigate whether HFOs correlate with the emergence of seizure activity and whether they differ between focal seizures (FSs) with impaired awareness and BTCSs. Methods: We retrospectively analyzed 15 FSs and 13 BTCSs from seven patients with mesial temporal lobe epilepsy, each of them with at least one BTCS and at least one FS. Representative intervals of intracranial electroencephalography from the seizure onset zone (SOZ) and remote non-SOZ areas were selected to compare pre-ictal, complex focal, tonic-clonic, and postictal periods. Ripples and fast ripples were visually identified and their density, that is, percentage of time occupied by the respective events, computed. Results: Ripple and fast ripple densities increased inside the SOZ after seizure onset (P < 0.01) and in remote areas after progression to BTCSs (P < 0.01). Postictal SOZ ripple density dropped below pre-ictal levels (P < 0.001). Prior to onset of bilateral tonic-clonic movements, ripple density inside the SOZ is higher in BTCSs than in FSs (P < 0.05). Interpretation: Ripples and fast ripples correlate with onset and spread of ictal activity. Abundant ripples inside the SOZ may reflect the activation of specific neuronal networks related to imminent spread of seizure activity.

Frontiers in Human Neuroscience, 2021

High-frequency oscillations (HFOs, ripples 80–250 Hz, fast ripples 250–500 Hz) are biomarkers of ... more High-frequency oscillations (HFOs, ripples 80–250 Hz, fast ripples 250–500 Hz) are biomarkers of epileptic tissue. They are most commonly observed over areas generating seizures and increase in occurrence during the ictal compared to the interictal period. It has been hypothesized that their rate correlates with the severity of epilepsy and seizure in affected individuals. In the present study, it was aimed to investigate whether the HFO count mirrors the observed behavioral seizure severity using a kainate rat model for temporal lobe epilepsy. Seizures were selected during the chronic epilepsy phase of this model and classified by behavioral severity according to the Racine scale. Seizures with Racine scale 5&6 were considered generalized and severe. HFOs were marked in 24 seizures during a preictal, ictal, and postictal EEG segment. The duration covered by the HFO during these different segments was analyzed and compared between mild and severe seizures. HFOs were significantly in...

Annals of Clinical and Translational Neurology, 2019

ObjectiveMany patients with epilepsy have both focal and bilateral tonic‐clonic seizures (BTCSs),... more ObjectiveMany patients with epilepsy have both focal and bilateral tonic‐clonic seizures (BTCSs), but it is largely unclear why ictal activity spreads only sometimes. Previous work indicates that interictal high‐frequency oscillations (HFOs), traditionally subdivided into ripples (80–250 Hz) and fast ripples (250–500 Hz), are a promising biomarker of epileptogenicity. We aimed to investigate whether HFOs correlate with the emergence of seizure activity and whether they differ between focal seizures (FSs) with impaired awareness and BTCSs.MethodsWe retrospectively analyzed 15 FSs and 13 BTCSs from seven patients with mesial temporal lobe epilepsy, each of them with at least one BTCS and at least one FS. Representative intervals of intracranial electroencephalography from the seizure onset zone (SOZ) and remote non‐SOZ areas were selected to compare pre‐ictal, complex focal, tonic‐clonic, and postictal periods. Ripples and fast ripples were visually identified and their density, that ...

Hochfrequenzoszillationen (HFO) im Bereich von 80-500 Hz gelten als vielversprechende Marker von ... more Hochfrequenzoszillationen (HFO) im Bereich von 80-500 Hz gelten als vielversprechende Marker von Epileptogenität. Ihre Anwendung finden sie vor allem im Bereich der prächirurgischen Epilepsiediagnostik zur Detektion zu resezierender Gehirnareale. Da die pathophysiologischen Mechanismen von HFO in der Anfallsgenese und -terminierung jedoch bislang nicht ausreichend erklärt sind, ist auch ihre Aussagekraft eingeschränkt. Bislang gibt es keine Informationen zu HFO und ihrem Vorkommen bei verschiedenen Anfallsstärken. In der vorliegenden Studie wurden HFO zunächst im Kainat-Rattenmodell und anschließend bei Patienten mit mesialer Temporallappenepilepsie analysiert. Es wurden 24 Anfälle von 2 Ratten in die Studie eingeschlossen. Nach visueller Analyse der EEG-Abschnitte mit einem Hochpassfilter wurden die Raten von HFO für einen jeweils 30-sekündigen präiktalen, iktalen und postiktalen Abschnitt berechnet und anschließend nach den verschiedenen Anfallsstärken aufgeteilt. Ripples (80-250 ...