Epilepsy research
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Acute brain insults, such as traumatic brain injury, status epilepticus, or stroke are common etiologies for the development of epilepsy, including temporal lobe epilepsy (TLE), which is often refractory to drug therapy. The mechanisms by which a brain injury can lead to epilepsy are poorly understood. It is well recognized that excessive glutamatergic activity plays a major role in the initial pathological and pathophysiological damage. ⋯ The amygdala, a temporal lobe structure that is most well known for its central role in emotional behavior, also plays a key role in epileptogenesis and epilepsy. In this article, we review the current knowledge on the pathology of the amygdala associated with epileptogenesis and/or epilepsy in TLE patients, and in animal models of TLE. In addition, because a derangement in the balance between glutamatergic and GABAergic synaptic transmission is a salient feature of hyperexcitable, epileptic neuronal circuits, we also review the information available on the role of the glutamatergic and GABAergic systems in epileptogenesis and epilepsy in the amygdala.
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To elucidate the pathophysiology of intractable epileptic spasms in older children by describing the interictal magnetoencephalography spike sources (MEGSSs), intracranial EEG ictal-onset zones (IOZs) and their ictal high-frequency oscillations (HFOs) and surgical outcomes. ⋯ Unilateral clusters of MEGSSs overlapped regional IOZs in older patients with epileptic spasms. High spatio-temporal MBFA before and during spasms revealed the regional ictal HFOs. Seizure-free outcomes following resection of zone with MEGSS clusters and ictal HFOs suggested that a subset of epileptic spasms was focal-onset seizures.
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We addressed the question whether lateralization of memory-related medial temporal lobe (MTL) activity in medial temporal lobe epilepsy (MTLE) patients is determined by pathology or sex, differentiating between two MTL subregions implicated in visuospatial memory as regions-of-interest (ROI) - the hippocampus (Hc) and the parahippocampal place area (PPA). We further assessed the relation between lateralization of hippocampal activation and postsurgical memory decline regarding performance in standardized neuropsychological tests of verbal and visuospatial learning. Functional magnetic resonance imaging (fMRI) data were acquired from unilateral MTLE patients performing an object location memory task in a virtual environment. ⋯ Lateralization of hippocampal activation was significantly correlated with decline in verbal learning after surgery. We were able to demonstrate that asymmetry of hippocampal fMRI-activation in unilateral MTLE patients is determined by the side of seizure focus, thus indicating the relative functional integrity of the hippocampi. This is corroborated by the finding that greater activation of the to-be-resected hippocampus leads to stronger verbal memory decline after surgery.
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The aim of the present study was to investigate whether sensitivity to flurothyl seizures after an acute methamphetamine (MA) administration is different in prenatally MA-exposed adult rats than in controls without prenatal drug exposure. Adult male and female rats exposed prenatally to MA (5mg/kg), saline or neither (controls) were divided into groups; one group received acute MA (1mg/kg s.c.) injection and the other group received saline. Rats were then challenged with flurothyl at a constant flow rate to induce seizures. ⋯ Estrous cycle influences did not lead to changes between groups of prenatal exposure or acute MA administration. Threshold of tonic-clonic seizures was increased in females in proestrus/estrus stage of the estrous cycle relative to diestrous females. Our study suggests that prenatal MA exposure affects the sensitivity of adult rats to the effect of acute MA treatment prior to flurothyl seizures relative to controls.
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Temporal lobe resection for epilepsy involves a risk of damaging the anterior part of the optic radiation, Meyer's loop, causing a contralateral upper quadrant visual field defect. This study aims to assess the intersubject variability in the course of Meyer's loop in vivo by diffusion tensor imaging and tractography. ⋯ Meyer's loop has a considerable variability in its anterior extent. Tractography may be a useful method to visualize Meyer's loop, and assess the risk of a visual field defect, prior to temporal lobe resection.