Preictal neuronal and vascular activity precedes the onset of childhood absence seizure: direct current potential shifts and their correlation with hemodynamic activity.

Significance Aims: The neurovascular mechanisms underlying the initiation of absence seizures and their dynamics are still not well understood. The objective of this study was to better noninvasively characterize the dynamics of the neuronal and vascular network at the transition from the interictal state to the ictal state of absence seizures and back to the interictal state using a combined electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and diffuse correlation spectroscopy (DCS) approach. The second objective was to develop hypotheses about the neuronal and vascular mechanisms that propel the networks to the 3-Hz spikes and wave discharges (SWDs) observed during absence seizures. Approaches: We evaluated the simultaneous changes in electrical (neuronal) and optical dynamics [hemodynamic, with changes in (Hb) and cerebral blood flow] of 8 pediatric patients experiencing 25 typical childhood absence seizures during the transition from the interictal state to the absence seizure by simultaneously performing EEG, fNIRS, and DCS. Results: Starting from ∼ 20 s before the onset of the SWD, we observed a transient direct current potential shift that correlated with alterations in functional fNIRS and DCS measurements of the cerebral hemodynamics detecting the preictal changes. Discussion: Our noninvasive multimodal approach highlights the dynamic interactions between the neuronal and vascular compartments that take place in the neuronal network near the time of the onset of absence seizures in a very specific cerebral hemodynamic environment. These noninvasive approaches contribute to a better understanding of the electrical hemodynamic environment prior to seizure onset. Whether this may ultimately be relevant for diagnostic and therapeutic approaches requires further evaluation.

Back to basics: the neuronal substrates and mechanisms that underlie the electroencephalogram in premature neonates.

Electroencephalography is the only clinically available technique that can address the premature neonate normal and pathological functional development week after week. The changes in the electroencephalogram (EEG) result from gradual structural and functional modifications that arise during the last trimester of pregnancy. Here, we review the structural changes over time that underlie the establishment of functional immature neural networks, the impact of certain anatomical specificities (fontanelles, connectivity, etc.) on the EEG, limitations in EEG interpretation, and the utility of high-resolution EEG (HR-EEG) in premature newborns (a promising technique with a high degree of spatiotemporal resolution). In particular, we classify EEG features according to whether they are manifestations of endogenous generators (i.e. theta activities that coalesce with a slow wave or delta brushes) or come from a broader network. Furthermore, we review publications on EEG in premature animals because the data provide a better understanding of what is happening in premature newborns. We then discuss the results and limitations of functional connectivity analyses in premature newborns. Lastly, we report on the magnetoelectroencephalographic studies of brain activity in the fetus. A better understanding of complex interactions at various structural and functional levels during normal neurodevelopment (as assessed using electroencephalography as a benchmark method) might lead to better clinical care and monitoring for premature neonates.

Normal EEG during the neonatal period: maturational aspects from premature to full-term newborns.

Electroencephalography (EEG) is the reference tool for the analysis of brain function, reflecting normal and pathological neuronal network activity. During the neonatal period, EEG patterns evolve weekly, according to gestational age. The first analytical criteria for the various maturational stages and standardized neonatal EEG terminology were published by a group of French neurophysiologists training in Paris (France) in 1999. These criteria, defined from analog EEG, were completed in 2010 with digital EEG analysis. Since then, this work has continued, aided by the technical progress in EEG acquisition, the improvement of knowledge on the maturating processes of neuronal networks, and the evolution of critical care. In this review, we present an exhaustive and didactic overview of EEG characteristics from extremely premature to full-term infants. This update is based on the scientific literature, enhanced by the study of normal EEGs of extremely premature infants by our group of neurophysiologists. For educational purposes, particular attention has been paid to illustrations using new digital tools.

Temporal and Spatial Dynamics of Different Interictal Epileptic Discharges: A Time-Frequency EEG Approach in Pediatric Focal Refractory Epilepsy.

Objective: Characterization of the spatial and temporal dynamics of interictal epileptic discharges (IED) using time-frequency analysis (TFA) and electrical-source localization (ESL). Methods: TFA was performed on IED (spikes, spike waves, and polyspike waves) recorded by high-density-EEG (HD-EEG) in 19 refractory focal epileptic children. Temporal modulations related to IEDs were analyzed in a time window around the IED peaks [-1,000 to 1,000 ms]. Spatial modulations were analyzed by ESL in the time-frequency and time domains. Results: IED were associated with complex power spectral modulations. We observed increases in power spectrum (IPS) patterns specific to IED type. For spikes, the TFA pattern consisted of an IPS (-100 to +100 ms, 4-50 Hz). For spike waves, the IPS was followed by a second IPS (+100 to +400 ms, 4-10 Hz), corresponding to the slow wave. IPS patterns were preceded (-400 to -100 ms, 4-40 Hz), and followed (+100 to +400 ms) by a decrease in the power spectrum (DPS) (n = 8). For 14 out of 19 patients, at least one ESL method was concordant with the epileptogenic area. For the remaining five patients, all of them had temporal epilepsies. ESL in the time-frequency domain (DPS/IPS) provided concordant (n = 6) or complementary (n = 4) information to the ESL in the time domain concerning the epileptogenic zone. ESL in time-frequency domain (DPS/IPS) was the only method to provide concordant information concerning the epileptogenic zone in three patients. Significance: TFA demonstrates complex time-frequency modulations of the neuronal networks around IED, suggesting that the pathological mechanisms are initiated well before onset of the classical hyper-synchronization of the IED. Combining time and time-frequency analysis of the ESL provides complementary information to define the epileptogenic zone in refractory focal epilepsy.

Stretch syncope or epileptic seizure? A pathologic hypothesis for self-induced stretch syncope.

We report on a 7-year-old female who presented paroxysmal episodes of loss of consciousness with clonic movements. The electroencephalogram (EEG) evidenced diffuse slow wave activations, with no symptoms. Epilepsy was suspected but antiepileptic drugs were ineffective. Video-EEG monitoring revealed that the syncope was triggered by stretching with a tachycardia that started during the stretch maneuver and diffuse slow waves on the EEG 2s before the symptoms. Stretch syncope can result in striking manifestations with subcortically driven clonic movements that can be mistaken for signs of epilepsy. Stretching might lead to transient hypoxia of the brainstem; in turn, this might activate the thalamocortical loop and thus generate cardiovascular changes, EEG slow waves, and physical manifestations.

Vagus nerve stimulation induces concomitant respiratory alterations and a decrease in SaO2 in children.

PURPOSE: To analyze respiratory alterations and effects on SaO(2) caused by vagus nerve stimulation (VNS) in children with epilepsy. METHODS: Polysomnographic recordings, including electroencephalography, thoracoabdominal distention, nasal airflow, SaO(2), and VNS artifact were evaluated in 10 children with pharmacoresistant epilepsy treated with VNS. RESULTS: Each VNS caused a significant increase in respiratory frequency (p < 0.05) throughout the stimulation period and a decrease in thoracoabdominal-distention amplitude (p < 0.05), especially at the beginning of the stimulation. These respiratory alterations induced a decrease in SaO(2) from 1 to 5%. The effects of VNS on respiration differed significantly between rapid-eye-movement (REM) and non-REM (NREM) sleep states. CONCLUSIONS: VNS caused a pronounced change in respiration in children with epilepsy, and this induced a decrease in SaO(2). It is possible that VNS has a neuroprotective effect, and this possibility calls for further investigation.