Search

Objective To evaluate whether structural and microstructural brain abnormalities in neonates with congenital heart disease (CHD) correlate with neuronal network dysfunction measured by analysis of EEG connectivity. Methods We studied a prospective cohort of 20 neonates with CHD who underwent continuous EEG monitoring before surgery to assess functional brain maturation and network connectivity, structural magnetic resonance imaging ( MRI) to determine the presence of brain injury and structural brain development, and diffusion tensor MRI to assess brain microstructural development. Results Neonates with MRI brain injury and delayed structural and microstructural brain development demonstrated significantly stronger high-frequency (beta and gamma frequency band) connectivity. Furthermore, neonates with delayed microstructural brain development demonstrated significantly weaker low-frequency (delta, theta, alpha frequency band) connectivity. Neonates with brain injury also displayed delayed functional maturation of EEG background activity, characterized by greater background discontinuity. Interpretation These data provide new evidence that early structural and microstructural developmental brain abnormalities can have immediate functional consequences that manifest as characteristic alterations of neuronal network connectivity. Such early perturbations of developing neuronal networks, if sustained, may be responsible for the persistent neurocognitive impairment prevalent in adolescent survivors of CHD. These foundational insights into the complex interplay between evolving brain structure and function may have relevance for a wide spectrum of neurological disorders manifesting early developmental brain injury. [ABSTRACT FROM AUTHOR]

The neuronal ceroid lipofuscinoses (NCL) are neurodegenerative conditions that associate cognitive decline, progressive cerebellar atrophy, retinopathy, and myoclonic epilepsy. NCL result from the excessive accumulation of neuronal and extraneuronal lipopigments, despite having diverse underlying biochemical aetiologies. Here we review the clinical presentation, pathophysiology and genetics of these conditions as well as the approach to diagnosis and management. [ABSTRACT FROM AUTHOR]

Anti–glutamic acid decarboxylase directed antibodies are a rare cause of autoimmune limbic encephalitis that is relatively resistant to immunotherapy. Here we report a 15-year-old boy with nonparaneoplastic, anti–glutamic acid decarboxylase limbic encephalitis presenting with subacute headache, memory disturbance, psychiatric symptoms, and seizures. At onset, his memory disturbance manifested as transient global amnesia-like episodes. Clinical remission was achieved with rituximab, intravenous immunoglobulin, and corticosteroids. [ABSTRACT FROM PUBLISHER]

Acute cerebral cortical trauma often leads to paroxysmal activities that terminate in a few hours, but several months later, patients can develop epilepsy. The process occurring between the initial acute triggered seizures and the onset of spontaneous unprovoked seizures is termed epileptogenesis. Here the authors summarize recent morphological, electrophysiological, and computational studies demonstrating that partial cortical isolation increases the number and duration of silent states in the cortical network, boosting neuronal connectivity and network excitability. These changes develop progressively, and after several weeks their synergetic action leads to epilepsy. [ABSTRACT FROM AUTHOR]

To study the possible mechanism(s) underlying unresponsiveness following neocortical seizures, we recorded excitatory postsynaptic potentials (EPSPs) of cortical neurons evoked by ipsilateral cortical stimulation before and after spontaneous or elicited seizures. Regular-spiking neurons (n = 32) were intracellularly recorded in association area five of cats under ketamine–xylazine or barbiturate anesthesia. Compared with control responses, cortically evoked EPSPs were characterized by decreased amplitude after electrographic seizures. Synaptic responses and intrinsic properties were measured by applying extracellular electrical stimuli followed by intracellular hyperpolarizing current pulses. The input resistance decreased during seizures but quickly recovered to control level after the paroxysms, whereas the amplitude of evoked EPSPs remained lower following seizures, generally for 2–12 min, suggesting that the decreased EPSPs were not due to an alteration of intrinsic response. Data demonstrate a long-lasting decreased synaptic responsiveness following generalized spike-wave seizures slowly recovering in time. [ABSTRACT FROM AUTHOR]

Global cerebral ischemia induces, within seconds, suppression of spontaneous electrocortical activity, partly due to alterations in synaptic transmission. In vitro studies have found that repeated brief hypoxic episodes prolong the persistence of synaptic transmission due to weakened adenosine release. The aim of this study was to investigate in vivo whether the time to ischemic electrocortical suppression ( TES) could be altered during energy stress conditions such as rapid repeated global cerebral ischemia and kainate-induced seizures. Experiments were carried out in adult rats under chloral hydrate anaesthesia. Repeated episodes of 1 min of ischemia were induced by transiently clamping the carotid arteries in a ‘four-vessel occlusion’ model. We devised an automatic method of TES estimation based on the decay of the root mean square of two-channel electrocorticographic recordings. To distinguish the alterations in spontaneous electrocortical activity we compared TES with the ischemic suppression of visual evoked potentials (VEP). During the first ischemic episode, TES was ∼ 15 s and remained unchanged when five ischemic episodes were separated by 10-min reperfusion intervals. When ischemia was repeated after 2 min of reperfusion TES progressively increased, reaching a plateau value of ∼ 24 s. A similar plateau was reached during kainate-induced seizures. The TES plateau occurred prior to ischemic suppression of VEP. Our data suggest that, under conditions of acute metabolic stress in vivo, the ischemic suppression of spontaneous electrocortical activity may be delayed up to a plateau value. These findings are consistent with the hypothesis of a depletable adenosine pool; however, the restoration of synaptic transmission may be faster in vivo than in vitro. [ABSTRACT FROM AUTHOR]

We studied the mechanisms underlying CO(2)-dependent DC potential shifts, using epicranial, epidural, epicortical, intraventricular, and intraparenchymal (intraneuronal, intraglial, and field) recordings in ketamine-xylazine-anesthetized cats. DC shifts were elicited by changes in artificial ventilation, causing end-tidal CO(2) variations within a 2-5% range. Hypercapnia was consistently associated with negative scalp DC shifts (average shift -284.4 microV/CO(2)%, range -216 to -324 microV/CO(2)%), whereas hypocapnia induced positive scalp DC shifts (average shift 307.8 microV/CO(2)%, range 234 to 342 microV/CO(2)%) in all electrodes referenced versus the nasium bone. The former condition markedly increased intracranial pressure (ICP), whereas the latter only slightly reduced ICP. Breakdown of the blood-brain barrier (BBB) resulted in a positive DC shift and drastically reduced subsequent DC responses to hypo-/hypercapnia. Thiopental and isoflurane also elicited a dose-dependent positive DC shift and, at higher doses, hypo-/hypercapnia responses displayed reverted polarity. As to the possible implication of neurons in the production of DC shifts, no polarity reversal was recorded between scalp, various intracortical layers, and deep brain structures. Moreover, the membrane potential of neurons and glia did not show either significant or systematic variations in association with the scalp-recorded CO(2)-dependent DC shifts. Pathological activities of neurons during spike-wave seizures produced DC shifts of significantly smaller amplitude than those generated by hyper-/hypocapnia. DC shifts were still elicited when neuronal circuits were silent during anesthesia-induced burst-suppression patterns. We suggest that potentials generated by the BBB are the major source of epicortical/cranial DC shifts recorded under conditions affecting brain pH and/or cerebral blood flow. [ABSTRACT FROM AUTHOR]