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Concept: Absence seizure

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Recent clinical studies revealed emotional and cognitive impairments associated with absence epilepsy. Preclinical research with genetic models of absence epilepsy however have primarily focused on dysfunctional emotional processes and paid relatively less attention to cognitive impairment. In order to bridge this gap, we investigated age-dependent changes in learning and memory performance, anxiety-like behavior, and locomotor activity of WAG/Rij rats (a valid model of generalized absence epilepsy) using passive avoidance, Morris water maze, elevated plus maze, and locomotor activity cage. We tested 5 month-old and 13 month-old WAG/Rij rats and compared their performance to age-matched Wistar rats. Results revealed a decline in emotional and spatial memory of WAG/Rij rats compared to age-matched Wistar rats only at 13 months of age. Importantly, there were no significant differences between WAG/Rij and Wistar rats in terms of anxiety-like behavior and locomotor activity at either age. Results pointed at age-dependent learning and memory deficits in the WAG/Rij rat model of absence epilepsy.

Concepts: Psychology, Cognitive psychology, Cognitive neuroscience, Rat, Performance, Pre-clinical development, Absence seizure, Laboratory rat

157

The prevalence of autism spectrum disorders (ASDs) has increased 20-fold over the past 50 years to >1% of US children. Although twin studies attest to a high degree of heritability, the genetic risk factors are still poorly understood. We analyzed data from two independent populations using u-statistics for genetically structured wide-locus data and added data from unrelated controls to explore epistasis. To account for systematic, but disease-unrelated differences in (non-randomized) genome-wide association studies (GWAS), a correlation between P-values and minor allele frequency with low granularity data and for conducting multiple tests in overlapping genetic regions, we present a novel study-specific criterion for ‘genome-wide significance’. From recent results in a comorbid disease, childhood absence epilepsy, we had hypothesized that axonal guidance and calcium signaling are involved in autism as well. Enrichment of the results in both studies with related genes confirms this hypothesis. Additional ASD-specific variations identified in this study suggest protracted growth factor signaling as causing more severe forms of ASD. Another cluster of related genes suggests chloride and potassium ion channels as additional ASD-specific drug targets. The involvement of growth factors suggests the time of accelerated neuronal growth and pruning at 9-24 months of age as the period during which treatment with ion channel modulators would be most effective in preventing progression to more severe forms of autism. By extension, the same computational biostatistics approach could yield profound insights into the etiology of many common diseases from the genetic data collected over the last decade.

Concepts: Gene, Genetics, Signal transduction, Action potential, Epilepsy, Absence seizure, Potassium channel, Neurological disorders

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Certain visual images, even in the absence of motion or flicker, can trigger seizures in patients with photosensitive epilepsy. As of yet, there is no systematic explanation as to why some static images are likely to provoke seizures, while others pose little or no risk. Here, we examined the neurophysiology literature to assess whether the pattern of neural responses in healthy visual cortex is predictive of the pathological responses in photosensitive epilepsy. Previous studies have suggested that gamma oscillations (30-80 Hz) measured in human visual cortex may play a role in seizure generation [1,2]. Recently, we and others have shown that increases in gamma band power can come from two very different cortical signals, one that is oscillatory (with a narrow peak between 30 Hz and 80 Hz), and another that is broadband[3]. The oscillatory signal arises from neuronal synchrony in the local population, while the broadband signal reflects the level of asynchronous neuronal activity, and is correlated with multiunit spiking [4]. These two responses have different biological origins and different selectivity for image properties. Here, we followed up on the previous proposals [1,2] to ask whether the image features that increase seizure likelihood in photosensitive epilepsy are linked to narrowband gamma oscillations specifically, or are associated with any kind of increase in visual activity. Based on published work, we compared pairs of image classes on a number of dimensions, and show that the type of image that elicits larger narrowband gamma oscillations in healthy visual cortex is also more likely to provoke seizures or pre-seizure activity in patients with photosensitive epilepsy. In contrast, images that elicit larger broadband, multiunit, or fMRI responses are much less predictive of seizure activity. We propose that a risk factor for seizures in patients with photosensitive epilepsy is engagement of the circuitry that produces gamma oscillations.

Concepts: Brain, Electroencephalography, Epilepsy, Seizure, Absence seizure, Myoclonus, Photosensitive epilepsy, Seizure trigger

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The notion of a level of consciousness is a key construct in the science of consciousness. Not only is the term employed to describe the global states of consciousness that are associated with post-comatose disorders, epileptic absence seizures, anaesthesia, and sleep, it plays an increasingly influential role in theoretical and methodological contexts. However, it is far from clear what precisely a level of consciousness is supposed to be. This paper argues that the levels-based framework for conceptualizing global states of consciousness is untenable and develops in its place a multidimensional account of global states.

Concepts: Scientific method, Consciousness, Epilepsy, Seizure, Absence seizure, Myoclonus, Unconscious mind, 8-Circuit Model of Consciousness

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To determine the prevalence of SLC2A1 mutations in children with early-onset absence epilepsy (EOAE) and to investigate whether there were differences in demographic and electroclinical data between patients who became seizure-free with anti-epileptic drug (AED) monotherapy (group I) and those who needed add-on treatment of a second AED (group II).

Concepts: DNA, Genetics, Evolution, DNA repair, Epilepsy, Seizure, Absence seizure, Diazepam

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The syndrome of malignant migrating partial seizures of infancy (MMPSI) is characterized by early onset of multiple seizure types and overall poor prognosis. Seizures are markedly drug resistant and few reports have suggested the efficacy of some antiepileptic drugs. We report one case of MMPSI in which prolonged seizure control is obtained with an association of clonazepam, levetiracetam and stiripentol, confirming thus the possibility of complete sustained seizure control in this epileptic syndrome. Of more than 60 cases reported to date, ours is the forth in which sustained complete control of seizures was obtained.

Concepts: Epilepsy, Anticonvulsant, Seizure, Status epilepticus, Absence seizure, Complex partial seizure, Diazepam, Atonic seizure

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Understanding the transition of brain activities towards an absence seizure, called pre-epileptic seizure, is a challenge. In this study, multiscale permutation entropy (MPE) is proposed to describe dynamical characteristics of electroencephalograph (EEG) recordings on different absence seizure states. The classification ability of the MPE measures using linear discriminant analysis is evaluated by a series of experiments. Compared to a traditional multiscale entropy method with 86.1% as its classification accuracy, the classification rate of MPE is 90.6%. Experimental results demonstrate there is a reduction of permutation entropy of EEG from the seizure-free state to the seizure state. Moreover, it is indicated that the dynamical characteristics of EEG data with MPE can identify the differences among seizure-free, pre-seizure and seizure states. This also supports the view that EEG has a detectable change prior to an absence seizure.

Concepts: Brain, Electroencephalography, Experiment, Seizure, Absence seizure, Dynamics, State, Linear discriminant analysis

28

Some patients with idiopathic/genetic generalized epilepsy (IGE) experience visual aura, which can confuse the diagnosis. We sought to determine the frequency and characteristics of visual auras in IGE patients. Among the 176 IGE patients, 4 men and 7 women reported visual auras (mean age - 24years). Syndromic diagnoses were juvenile myoclonic epilepsy in four, eyelid myoclonia with absences (EMA) in three, juvenile absence epilepsy in three, and other in one. Visual auras consisted of flashing lights, macropsia, illusional movements, and blindness. Eyelid myoclonia with absences was significantly more common in the group with visual aura (3 of 11 patients vs. 8 of 165 IGE patients; P=0.02). Furthermore, photosensitivity was found significantly more common in IGE patients with visual aura (90% vs 46% of the total IGE patients) (P=0.004). In conclusion, the visual auras do not exclude a diagnosis of IGE. The presence of visual aura in the EMA syndrome is also remarkable.

Concepts: Medical terms, Epilepsy, Seizure, Absence seizure, Myoclonus, Neurological disorders, Childhood absence epilepsy, Juvenile myoclonic epilepsy

27

The aim of this observational study was to obtain information regarding efficacy and safety of add-on levetiracetam (LEV; n=32) in Japanese patients with refractory partial seizures in an everyday clinical setting, relative to control AEDs (n=30). This is the first study of LEV add-on therapy conducted in Japan since approval was made. The medical charts of patients were retrospectively reviewed. The efficacy variables were seizure freedom and ≥50% reduction in seizure frequency. A significantly higher response to LEV was demonstrated in patients with all seizure types at baseline, relative to control AEDs. In patients with a duration of epilepsy of at least 10 years, significant effects in response to LEV were demonstrated with regards to efficacy variables, relative to control AEDs, thus providing meaningful results. Only two patients (6.2%) discontinued LEV treatment due to worsening of seizures, but no discontinuation was reported due to adverse events. LEV as add-on therapy to other AEDs is a promising useful treatment option for patients with refractory partial seizures without notable effects on safety, indicating that this treatment regimen might be recommended for such patients.

Concepts: Epilepsy, Anticonvulsant, Seizure, Status epilepticus, Absence seizure, Complex partial seizure, Postictal state, Myoclonus

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BACKGROUND AND PURPOSE: Interictal headache (IIH), and in particular migraine, is considered a relevant co-morbidity in epilepsy; however, available data are ambiguous. Periictal headache (PIH) displays a frequent ancillary burden to seizures, but identification of unequivocal predictors is still elusive. METHODS: All patients (≥ 18 years) with epilepsy or unprovoked seizures seen in a tertiary epilepsy outpatient clinic underwent a semi-structured interview regarding occurrence and characteristics of IIH and PIH. Clinical variables in patients with and without IIH and PIH and seizure types with and without PIH were compared. RESULTS: Out of 201 patients, 56.2% reported headache, IIH occurred in 34.3% and 10.9% suffered from migraine. PIH was reported by 35.3%, occurring preictally in 16 and postictally in 61 cases. PIH character was migrainous in 26.8% and tension-type headache-like in 62%, mean severity was 6.1 ± 2.2 cm. PIH was treated analgetically by less than 40% of patients, only 11% sought specific medical advice. Predictors were low age at epilepsy onset (OR 0.963, 95% CI 0.945-0.981, P < 0.0001), antiepileptic drug (AED) polytherapy (OR 1.943, 95% CI 1.046-3.612, P = 0.036) and generalized tonic-clonic seizures (P < 0.0001). CONCLUSIONS: In patients with epilepsy, IIH, and particularly migraine, is less common than expected, challenging the widely held concept of co-morbidity of the two conditions. PIH is frequent, severe and undertreated. Predictors include low age at epilepsy onset, AED polytherapy and tonic-clonic generalized seizures. Physicians should ask for PIH and offer specific analgesic treatment. To confirm these findings, future studies with a prospective approach implementing a headache and seizure diary should be performed.

Concepts: Neurology, Epilepsy, Anticonvulsant, Seizure, Status epilepticus, Absence seizure, Diazepam, Tonic–clonic seizure