Current and emerging treatments for absence seizures in young patients

In this report, we review the pharmacological and non-pharmacological treatments of the different absence seizure types as recently recognized by the International League Against Epilepsy: typical absences, atypical absences, myoclonic absences, and eyelid myoclonia with absences. Overall, valproate and ethosuximide remain the principal anti-absence drugs. Typical absence seizures exhibit a specific electroclinical semiology, pathophysiology, and pharmacological response profile. A large-scale comparative study has recently confirmed the key role of ethosuximide in the treatment of childhood absence epilepsy, more than 50 years after its introduction. No new antiepileptic drug has proven major efficacy against typical absences. Of the medications under development, brivaracetam might be an efficacious anti-absence drug. Some experimental drugs also show efficacy in animal models of typical absence seizures. The treatment of other absence seizure types is not supported with a high level of evidence. Rufinamide appears to be the most promising new antiepileptic drug for atypical absences and possibly for myoclonic absences. The efficacy of vagal nerve stimulation should be further evaluated for atypical absences. Levetiracetam appears to display a particular efficacy in eyelid myoclonia with absences. Finally, it is important to remember that the majority of antiepileptic drugs, whether they be old or new, may aggravate typical and atypical absence seizures

Natural history of KBG syndrome in a large European cohort

KBG syndrome (KBGS) is characterized by distinctive facial gestalt, short stature and variable clinical findings. With ageing, some features become more recognizable, allowing a differential diagnosis. We aimed to better characterize natural history of KBGS. In the context of a European collaborative study, we collected the largest cohort of KBGS patients (49). A combined array- based Comparative Genomic Hybridization and next generation sequencing (NGS) approach investigated both genomic Copy Number Variants and SNVs. Intellectual disability (ID) (82%) ranged from mild to moderate with severe ID identified in two patients. Epilepsy was present in 26.5%. Short stature was consistent over time, while occipitofrontal circumference (median value: -0.88 SD at birth) normalized over years. Cerebral anomalies, were identified in 56% of patients and thus represented the second most relevant clinical feature reinforcing clinical suspicion in the paediatric age when short stature and vertebral/dental anomalies are vague. Macrodontia, oligodontia and dental agenesis (53%) were almost as frequent as skeletal anomalies, such as brachydactyly, short fifth finger, fifth finger clinodactyly, pectus excavatum/carinatum, delayed bone age. In 28.5% of individuals, prenatal ultrasound anomalies were reported. Except for three splicing variants, leading to a premature termination, variants were almost all frameshift. Our results, broadening the spectrum of KBGS phenotype progression, provide useful tools to facilitate differential diagnosis and improve clinical management. We suggest to consider a wider range of dental anomalies before excluding diagnosis and to perform a careful odontoiatric/ear-nose-throat (ENT) evaluation in order to look for even submucosal palate cleft given the high percentage of palate abnormalities. NGS approaches, following evidence of antenatal ultrasound anomalies, should include ANKRD11.</p

<i>GRIN2A</i>-related disorders:genotype and functional consequence predict phenotype

Alterations of the N-methyl-d-aspartate receptor (NMDAR) subunit GluN2A, encoded by GRIN2A, have been associated with a spectrum of neurodevelopmental disorders with prominent speech-related features, and epilepsy. We performed a comprehensive assessment of phenotypes with a standardized questionnaire in 92 previously unreported individuals with GRIN2A-related disorders. Applying the criteria of the American College of Medical Genetics and Genomics to all published variants yielded 156 additional cases with pathogenic or likely pathogenic variants in GRIN2A, resulting in a total of 248 individuals. The phenotypic spectrum ranged from normal or near-normal development with mild epilepsy and speech delay/apraxia to severe developmental and epileptic encephalopathy, often within the epilepsy-aphasia spectrum. We found that pathogenic missense variants in transmembrane and linker domains (misTMD+Linker) were associated with severe developmental phenotypes, whereas missense variants within amino terminal or ligand-binding domains (misATD+LBD) and null variants led to less severe developmental phenotypes, which we confirmed in a discovery (P = 10-6) as well as validation cohort (P = 0.0003). Other phenotypes such as MRI abnormalities and epilepsy types were also significantly different between the two groups. Notably, this was paralleled by electrophysiology data, where misTMD+Linker predominantly led to NMDAR gain-of-function, while misATD+LBD exclusively caused NMDAR loss-of-function. With respect to null variants, we show that Grin2a+/- cortical rat neurons also had reduced NMDAR function and there was no evidence of previously postulated compensatory overexpression of GluN2B. We demonstrate that null variants and misATD+LBD of GRIN2A do not only share the same clinical spectrum (i.e. milder phenotypes), but also result in similar electrophysiological consequences (loss-of-function) opposing those of misTMD+Linker (severe phenotypes; predominantly gain-of-function). This new pathomechanistic model may ultimately help in predicting phenotype severity as well as eligibility for potential precision medicine approaches in GRIN2A-related disorders

Electrophysiological characterisation of myoclonic-atonic seizures in symptomatic continuous spike-waves during slow sleep syndrome.

Sudden epileptic falls are frequently reported in continuous spike-waves during slow sleep (CSWS) syndrome. Inhibitory seizures are usually considered as the underlying mechanism. However, published polygraphic recordings are rare. We report the case of a 22 month-old boy suffering from a symptomatic CSWS syndrome associated with a perinatal stroke involving the right middle cerebral artery territory. He presented with psychomotor regression and daily multiple falls related to myoclonic-atonic seizures. Neurophysiological examination showed secondary generalized myoclonus systematically correlated with a bilateral spike spreading from the right central area. This confirms that positive myoclonus, in addition to negative myoclonus, may be responsible for epileptic falls in CSWS syndrome. [Published with video sequences]

Adult-onset Rasmussen encephalitis associated with focal cortical dysplasia

Rasmussen encephalitis is a rare, devastating condition, typically presenting in childhood. Cases of adult-onset Rasmussen have also been described, but the clinical picture is less defined, rendering final diagnosis difficult. We present a case of adult-onset Rasmussen encephalitis with dual pathology, associated with focal cortical dysplasia and encephalitis. We interpreted the Rasmussen encephalitis to be caused by severe and continuous epileptic activity due to focal cortical dysplasia. The best therapeutic approach for such cases remains unclear

Topiramate in childhood epileptic encephalopathy with continuous spike-waves during sleep: A retrospective study of 21 cases.

OBJECTIVE: Encephalopathy with continuous spike-wave during sleep (CSWS) is a particularly difficult-to-treat childhood epileptic syndrome. This study sought to present the EEG improvement and clinical efficacy of topiramate (TPM), a broad spectrum antiepileptic drug (AED), in a series of 21 children with CSWS encephalopathy. METHODS: We retrospectively reviewed the EEG results and clinical data of children with CSWS followed-up in our institution and treated with TPM. Sleep EEGs were performed 0-3 months prior to TPM introduction and then at 3 and 12 months. The exclusion criteria were (1) introduction of another AED and (2) withdrawal of a potentially aggravating AED during the first 3 months of treatment. In addition to spike index (SI), the severity of EEG abnormalities was rated using an original scale that also considered the spatial extent of interictal epileptiform discharges. RESULTS: 21 patients were included (18 males, 4-14y, three symptomatic cases). At 3 months, sleep EEG was improved in 14 and normalized in four (TPM doses: 2-5.5 mg/kg/day). Among these 18 patients, 16 manifested cognitive or behavioural improvement. In a subgroup of seven patients with frequent seizures, five became seizure-free and one had over 75% decrease in seizure frequency. At the one-year follow-up, 20 children were still on TPM and 10 exhibited persistent EEG improvement without any other AED being introduced, most of them with clinical benefits. CONCLUSION: TPM can decrease EEG abnormalities in epileptic encephalopathy with CSWS, achieving clinical improvement in the majority of patients. However, relapse may occur in the long-term in nearly half of cases. Otherwise, TPM has proven particularly useful in reducing seizure frequency in refractory cases

Additional clinical value of voxel-based morphometric MRI post-processing for MRI-negative epilepsies: a prospective study.

Magnetic resonance imaging is of paramount importance in the presurgical evaluation of drug resistant epilepsy. Detection of a potentially epileptogenic lesion significantly improves seizure outcome after surgery. To optimize the detection of subtle lesions, MRI post-processing techniques may be of essential help. In this study, we aimed to evaluate the detection rate of the voxel-based morphometric analysis program (MAP) in a prospective trial. We aimed to study the MAP+ findings in terms of their clinical value in the decision-making process of the presurgical evaluation. We included, prospectively, 21 patients who had negative MRI by visual analysis. In a first step, results of the conventional non-invasive presurgical evaluation were discussed, blinded to the MAP results, in multidisciplinary patient management conferences to determine the possible seizure onset zone and to set surgical or invasive evaluation plans. Thereafter, MAP results were presented, and the change of initial clinical plan was recorded. All MAP detections were reaffirmed by a neuroradiologist with epilepsy expertise. For the 21 patients included, mean age at the time of patient management conference was 26 years (SD 15 +/- years, range: 5-54 years). In total, 4/21 had temporal lobe epilepsy and 17/21 had extra-temporal lobe epilepsy. MAP was positive in 10/21 (47%) patients and in 6/10 (60%) a diagnosis of focal cortical dysplasia was confirmed after neuroradiologist review, corresponding to a 28% detection rate. MAP+ findings had a clear impact on the initial management in 7/10 patients (7/21, 33% of all patients), which included an adaptation of the intracranial EEG plan (6/7 patients), or the decision to proceed directly to surgery (1/7 patients). MRI post-processing using the MAP method yielded an increased detection rate of 28% for subtle dysplastic lesions in a prospective cohort of MRI-negative patients, indicating its potential value in epilepsy presurgical evaluation