High frequency oscillations can pinpoint seizures progressing to status epilepticus

Abstract

Status epilepticus (SE) is defined as a seizure lasting more than 5 min or a period of recurrent seizures without recovery between them. SE is a serious emergency condition that requires immediate intervention; therefore, identifying SE electrophysiological markers may translate in prompt care to stop it. Here, we analyzed the EEG signals recorded from the CA3 region of the hippocampus and the entorhinal cortex in rats that responded to systemic administration of 4-aminopyridine (4AP) by generating either isolated seizures or seizures progressing to SE. We found that high frequency oscillations (HFOs) -which can be categorized as ripples and fast ripples (250-500 Hz) -had different patterns of occurrence in the two groups (n = 5 for each group). Specifically, fast ripples in CA3 and entorhinal cortex of the SE group occurred at higher rates than ripples, both during the ictal and post-ictal periods when compared to the HFOs recorded from the isolated seizure group. Our data reveal that different patterns of HFO occurrence can pinpoint seizures progressing to SE, thus suggesting the involvement of different neuronal networks at the termination of seizure discharges.

Interictal oscillations and focal epileptic disorders

“…Indeed, this is a serious emergency condition that requires immediate intervention; therefore, identifying electrophysiological markers of an upcoming status epilepticus may translate in prompt care to stop it. In a recent study, Salami et al (2016) have found that specific interictal oscillations can pinpoint to experimental conditions that are likely to generate either an isolated seizure (Fig. 4A) or to progress to status epilepticus (Fig.…”

“…In a recent study, Salami et al . () have found that specific interictal oscillations can pinpoint to experimental conditions that are likely to generate either an isolated seizure (Fig. A) or to progress to status epilepticus (Fig.…”

“…However, fast ripples tend to occur at higher rates during the post-ictal period (*P < 0.05) in the status epilepticus group (panel b). Data were obtained from the experiments published in Salami et al (2016). predominated in the hippocampus CA3 area. In addition, the duration of type 2 spikes (i.e.…”

Preictal variability of high‐frequency oscillation rates in refractory epilepsy

“…8 As high-frequency activity has been shown to increase prior to seizure onset both clinically and in experimental models, [9][10][11] some have also hypothesized a link between HFOs, the mechanisms of ictogenesis, and preictal brain states. [10][11][12][13][14][15][16][17][18] The existence of a preictal state is still unproven, but growing evidence suggests it is measurable in many patients. [19][20][21] One notable study found differences in preictal electroencephalogram (EEG) occurring even hours before seizure onset.…”

HFO to Measure Seizure Propensity and Improve Prognostication in Patients With Epilepsy

“…[36][37][38] A higher number of ictal fast ripples was found in rats with seizures progressing to status epilepticus than in rats with focal seizures. 39 Using intracranial EEG, Schöenberger and coworkers showed that within the same individuals HFO rates were high in seizures that progressed to secondary generalization compared with those that remained focal. 40 This difference between seizure types was visible prior to the clinical occurrence of secondary generalization.…”