Loss of glutamate transporter eaat2a leads to aberrant neuronal excitability, recurrent epileptic seizures, and basal hypoactivity.

Astroglial excitatory amino acid transporter 2 (EAAT2, GLT-1, and SLC1A2) regulates the duration and extent of neuronal excitation by removing glutamate from the synaptic cleft. Hence, an impairment in EAAT2 function could lead to an imbalanced brain network excitability. Here, we investigated the functional alterations of neuronal and astroglial networks associated with the loss of function in the astroglia predominant eaat2a gene in zebrafish. We observed that eaat2a-/- mutant zebrafish larvae display recurrent spontaneous and light-induced seizures in neurons and astroglia, which coincide with an abrupt increase in extracellular glutamate levels. In stark contrast to this hyperexcitability, basal neuronal and astroglial activity was surprisingly reduced in eaat2a-/- mutant animals, which manifested in decreased overall locomotion. Our results reveal an essential and mechanistic contribution of EAAT2a in balancing brain excitability, and its direct link to epileptic seizures.

Elevated photic response is followed by a rapid decay and depressed state in ictogenic networks.

OBJECTIVE: The switch between nonseizure and seizure states involves profound alterations in network excitability and synchrony. In this study, we aimed to identify and compare features of neural excitability and dynamics across multiple zebrafish seizure and epilepsy models. METHODS: Inspired by video-electroencephalographic recordings in patients, we developed a framework to study spontaneous and photically evoked neural and locomotor activity in zebrafish larvae, by combining high-throughput behavioral tracking and whole-brain in vivo two-photon calcium imaging. RESULTS: Our setup allowed us to dissect behavioral and physiological features that are divergent or convergent across multiple models. We observed that spontaneous locomotor and neural activity exhibit great diversity across models. Nonetheless, during photic stimulation, hyperexcitability and rapid response dynamics were well conserved across multiple models, highlighting the reliability of photically evoked activity for high-throughput assays. Intriguingly, in several models, we observed that the initial elevated photic response is often followed by rapid decay of neural activity and a prominent depressed state. Elevated photic response and following depressed state in seizure-prone networks are significantly reduced by the antiseizure medication valproic acid. Finally, rapid decay and depression of neural activity following photic stimulation temporally overlap with slow recruitment of astroglial calcium signals that are enhanced in seizure-prone networks. SIGNIFICANCE: We argue that fast decay of neural activity and depressed states following photic response are likely due to homeostatic mechanisms triggered by excessive neural activity. An improved understanding of the interplay between elevated and depressed excitability states might suggest tailored epilepsy therapies.

Remarkable effect of transdermal nicotine in children with CHRNA4-related autosomal dominant sleep-related hypermotor epilepsy.

OBJECTIVE: Autosomal dominant sleep-related hypermotor epilepsy (ADSHE) is characterized by hypermotor seizures and may be caused by gain-of-function mutations affecting the nicotinic acetylcholine receptor (nAChR). Benefit from nicotine consumption has been reported in adult patients with this disorder. For the first time, the effect of transdermal nicotine is evaluated in children. METHODS: Transdermal nicotine was applied to three boys, two aged 10 years (7 mg/24 h) and one six years (3.5 mg/24 h). Autosomal dominant sleep-related hypermotor epilepsy was caused by the p.S280F-CHRNA4 (cholinergic receptor, nicotinic, alpha polypeptide 4) mutation. The children suffered from frequent, persistent nocturnal seizures and had developed educational and psychosocial problems. Seizure frequency and cognitive and behavioral parameters were assessed before and after treatment. RESULTS: A striking seizure reduction was reported soon after treatment onset. Hypermotor seizures disappeared; only sporadic arousals, sometimes with minor motor elements, were observed. Psychometric testing documented improvement in cognitive domains such as visuospatial ability, processing speed, memory, and some areas of executive functions. SIGNIFICANCE: Nicotine appears to be a mechanistic treatment for this specific disorder, probably because of desensitization of the mutated receptors. It may control seizures resistant to conventional drugs for epilepsy and impact socioeducational function in children. This mode of precision therapy should receive more attention and should be available to more patients with uncontrolled CHRNA4-related ADSHE across the age span.

The spectrum of pyridoxine dependent epilepsy across the age span: A nationwide retrospective observational study.

BACKGROUND: Pyridoxine-dependent epilepsy (PDE) is a rare seizure disorder usually presenting with neonatal seizures. Most cases are caused by biallelic pathogenic ALDH7A1variants. While anti-seizure medications are ineffective, pyridoxine provides seizure control, and dietary interventions may be of benefit. As the natural history beyond adolescence is insufficiently explored, our study aimed to assess the spectrum of PDE at various ages in Norway. METHODS: Patients were ascertained by contacting all Norwegian paediatric, neurological, and neurohabilitation departments and relevant professional societies. Medical records were collected and reviewed. RESULTS: We identified 15 patients treated for PDE; 13 had ALDH7A1 variants (PDE-ALDH7A1), one had PNPO deficiency, and in one, aetiology remained obscure. Of those with PDE-ALDH7A1, 12 were alive at time of study; five were > 18 years old and six were < 4 years. Median age was 10 years (range 2 months-53 years). Estimated minimum prevalence was 6.3/million among children and 1.2/million among adults. Ten had seizure onset on the first day of life. Perinatal complications and neuroradiological abnormalities suggested additional seizure aetiologies in several patients. Pyridoxine had immediate effect in six, while six had delayed (>1 h) or uncertain effect. Median delay from first seizure to continuous treatment was 11 days (range 0-42). Nine experienced breakthrough seizures with intercurrent disease or due to pyridoxine discontinuation. Cognitive outcomes ranged from normal to severe intellectual disability. The condition appeared to remain stable in adult life. SIGNIFICANCE: We found a much higher prevalence of PDE-ALDH7A1 in children relative to adults, suggesting previous underdiagnosis and early mortality. Perinatal complications are common and can delay diagnosis and initiation of pyridoxine treatment. Lifelong and continuous treatment with pyridoxine is imperative. Due to better diagnostics and survival, the number of adult patients is expected to rise.

Precision treatment with nicotine in autosomal dominant sleep-related hypermotor epilepsy (ADSHE): An observational study of clinical outcome and serum cotinine levels in 17 patients.

PURPOSE: To report the clinical outcome of nicotine exposure in patients with autosomal dominant sleep-related hypermotor epilepsy (ADSHE), along with serum concentrations of the major nicotine metabolite cotinine. METHODS: We recruited 17 ADSHE patients with CHRNA4 mutations (12 with p.S280F and 5 with p.L291 dup). Clinical characteristics were collected from hospital records. A telephone interview was performed on the use and seizure-reducing effect of nicotine applying a six-point rating scale from "none" to very good". Serum concentrations of cotinine were measured in 14 nicotine users. RESULTS: All patients but one had ever used nicotine. Nine had used snuff; seven were current users. Eleven had used transdermal nicotine; nine were current users. Seven reported long-lasting seizure control, all used nicotine, four transdermal nicotine and three snuff. In 78% of patients using continuous transdermal nicotine, the effect was rated as good or very good. Cotinine concentrations were 453 ± 196 (mean ± SD) nmol/l in seven patients using transdermal nicotine only vs. 1241 ± 494 nmol/l in seven using other forms of nicotine. No correlation with seizure control was found. Three patients experienced improvement with transdermal delivery compared to snuff. CONCLUSION: This is the hitherto largest observational study supporting a favorable effect of nicotine in this specific seizure disorder. Better seizure control from transdermal nicotine compared to only day-time consumption suggests benefit from exposure throughout the night. According to current clinical experience, patients with uncontrolled ADSHE harboring relevant mutations should be offered precision treatment with transdermal nicotine.

Glia-neuron interactions underlie state transitions to generalized seizures.

Brain activity and connectivity alter drastically during epileptic seizures. The brain networks shift from a balanced resting state to a hyperactive and hypersynchronous state. It is, however, less clear which mechanisms underlie the state transitions. By studying neural and glial activity in zebrafish models of epileptic seizures, we observe striking differences between these networks. During the preictal period, neurons display a small increase in synchronous activity only locally, while the gap-junction-coupled glial network was highly active and strongly synchronized across large distances. The transition from a preictal state to a generalized seizure leads to an abrupt increase in neural activity and connectivity, which is accompanied by a strong alteration in glia-neuron interactions and a massive increase in extracellular glutamate. Optogenetic activation of glia excites nearby neurons through the action of glutamate and gap junctions, emphasizing a potential role for glia-glia and glia-neuron connections in the generation of epileptic seizures.

Early Thrombectomy of a Proximal Middle Cerebral Artery Occlusion Leading to Complete Recovery with No Infarct.

Many recent trials show the benefit of mechanical thrombectomy in acute ischemic stroke caused by thrombi lodged in large arteries. We report the case of a 55-year-old patient who developed sudden-onset right-sided hemiplegia and aphasia. Computed tomography angiography showed a thrombus in the M1 segment of the left middle cerebral artery. The thrombus was removed by mechanical thrombectomy 85 min after the onset of symptoms. A magnetic resonance imaging (MRI) scan showed no infarct, and the patient was discharged symptom free. To the best of our knowledge, this is the first report of thrombectomy of a symptomatic proximal middle cerebral artery occlusion leading to complete rescue, both clinically and radiologically assessed by MRI. Our case report shows that an early thrombectomy can provide an excellent outcome.