Recurrent KIF2A mutations are responsible for classic lissencephaly.

Kinesins play a critical role in the organization and dynamics of the microtubule cytoskeleton, making them central players in neuronal proliferation, neuronal migration, and postmigrational development. Recently, KIF2A mutations were identified in cortical malformation syndromes associated with microcephaly. Here, we detected two de novo p.Ser317Asn and p.His321Pro mutations in KIF2A in two patients with lissencephaly and microcephaly. In parallel, we re-evaluated the two previously reported cases showing de novo mutations of the same residues. The identification of mutations only in the residues Ser317 and His321 suggests these are hotspots for de novo mutations. Both mutations lead to a classic form of lissencephaly, with a posterior to anterior gradient, almost indistinguishable from LIS1-related lissencephaly. However, three fourths of patients also showed variable congenital and postnatal microcephaly, up to -5 SD. Located in the motor domain of the KIF2A protein, the Ser317 and His321 alterations are expected to disrupt binding or hydrolysis of ATP and consequently the MT depolymerizing activity. This report also establishes that KIF2A mutations represent significant causes of classic lissencephaly with microcephaly.

Mutations in ISPD cause Walker-Warburg syndrome and defective glycosylation of α-dystroglycan.

Walker-Warburg syndrome (WWS) is an autosomal recessive multisystem disorder characterized by complex eye and brain abnormalities with congenital muscular dystrophy (CMD) and aberrant a-dystroglycan glycosylation. Here we report mutations in the ISPD gene (encoding isoprenoid synthase domain containing) as the second most common cause of WWS. Bacterial IspD is a nucleotidyl transferase belonging to a large glycosyltransferase family, but the role of the orthologous protein in chordates is obscure to date, as this phylum does not have the corresponding non-mevalonate isoprenoid biosynthesis pathway. Knockdown of ispd in zebrafish recapitulates the human WWS phenotype with hydrocephalus, reduced eye size, muscle degeneration and hypoglycosylated a-dystroglycan. These results implicate ISPD in a-dystroglycan glycosylation in maintaining sarcolemma integrity in vertebrates.

Mutations in SWI/SNF chromatin remodeling complex gene ARID1B cause Coffin-Siris syndrome.

We identified de novo truncating mutations in ARID1B in three individuals with Coffin-Siris syndrome (CSS) by exome sequencing. Array-based copy-number variation (CNV) analysis in 2,000 individuals with intellectual disability revealed deletions encompassing ARID1B in 3 subjects with phenotypes partially overlapping that of CSS. Taken together with published data, these results indicate that haploinsufficiency of the ARID1B gene, which encodes an epigenetic modifier of chromatin structure, is an important cause of CSS and is potentially a common cause of intellectual disability and speech impairment.

Presence of ATM protein and residual kinase activity correlates with the phenotype in ataxia-telangiectasia: a genotype-phenotype study.

Ataxia-telangiectasia (A-T) is an autosomal recessive neurodegenerative disorder with multisystem involvement and cancer predisposition, caused by mutations in the A-T mutated (ATM) gene. To study genotype-phenotype correlations, we evaluated the clinical and laboratory data of 51 genetically proven A-T patients, and additionally measured ATM protein expression and kinase activity. Patients without ATM kinase activity showed the classical phenotype. The presence of ATM protein, correlated with slightly better immunological function. Residual kinase activity correlated with a milder and essentially different neurological phenotype, absence of telangiectasia, normal endocrine and pulmonary function, normal immunoglobulins, significantly lower X-ray hypersensitivity in lymphocytes, and extended lifespan. In these patients, cancer occurred later in life and generally consisted of solid instead of lymphoid malignancies. The genotypes of severely affected patients generally included truncating mutations resulting in total absence of ATM kinase activity, while patients with milder phenotypes harbored at least one missense or splice site mutation resulting in expression of ATM with some kinase activity. Overall, the phenotypic manifestations in A-T show a continuous spectrum from severe classical childhood-onset A-T to a relatively mild adult-onset disorder, depending on the presence of ATM protein and kinase activity. Each patient is left with a tremendously increased cancer risk.

Long term outcome of benign childhood epilepsy with centrotemporal spikes: Dutch Study of Epilepsy in Childhood.

PURPOSE: To determine long-term outcome in a cohort of children with newly diagnosed benign childhood epilepsy with centrotemporal spikes (BECTS). METHODS: 29 children with BECTS were included in the Dutch Study of Epilepsy in Childhood. Each child was followed for 5 years, and subsequently contacted 12-17 years after enrolment to complete a structured questionnaire. Twenty children had typical BECTS, nine had atypical BECTS (age at onset <4 years, developmental delay or learning difficulties at inclusion, other seizure types, atypical EEG abnormalities). RESULTS: Mean age at onset of epilepsy was 8.0 years with slight male preponderance. Most common seizure-types before enrolment were generalized tonic-clonic seizures (GTCS) and simple partial seizures; in 86% of the children seizures occurred during sleep. After 12-17 years, 96% had a terminal remission (TR(F)) of more than 5 years and 89% of more than 10 years. Mean duration of epilepsy was 2.7 years; mean age at reaching TR(F) was 10.6 years. Many children (63%) had experienced one or more (secondary) GTCS. Antiepileptic drugs were used by 79% of the children with a mean duration of 3.0 years. None of the children seemed to have developed learning problems or an arrest of cognitive development during follow-up. No significant differences were observed in patient characteristics or outcome between children with typical BECTS and children with atypical BECTS. CONCLUSIONS: All children in our cohort, both those with typical and atypical BECTS, had a very good prognosis with high remission rates after 12-17 years. None of the predictive factors for disease course and outcome observed in earlier studies (other seizure types, age at onset, multiple seizures at onset) were prognostic in our cohort.

Long-term outcome of childhood absence epilepsy: Dutch Study of Epilepsy in Childhood.

SUMMARY: We determined long-term outcome and the predictive value of baseline and EEG characteristics on seizure activity evolution in 47 children with newly diagnosed childhood absence epilepsy (CAE) included in the Dutch Study of Epilepsy in Childhood. All children were followed for 12-17 years. The children were subdivided in three groups for the analyses: those becoming seizure-free (I) within 1 month after enrolment; (II) 1-6 months after enrolment; and (III) more than 6 months after enrolment or having seizures continuing during follow-up. No significant differences were observed between groups in sex, age at onset, occurrence of febrile seizures, and positive first-degree family history for epilepsy. All groups had high remission rates after 12-17 years. Significantly more relapses occurred in group III than in group I. Total duration of epilepsy and mean age at final remission were 3.9 and 9.5 years, respectively, being significantly longer and higher in group III than in groups I and II. In all groups only a small number of children (total 13%) developed generalized tonic-clonic seizures. In conclusion, our children with CAE had an overall good prognosis with few children (7%) still having seizures after 12-17 years. Remission rate in children with CAE cannot be predicted on the basis of baseline and EEG characteristics. The early clinical course (i.e. the first 6 months) has some predictive value with respect to the total duration of absence epilepsy.

Add-on levetiracetam in children and adolescents with refractory epilepsy: results of an open-label multi-centre study.

PURPOSE: To study the efficacy and tolerability of add-on levetiracetam in children and adolescents with refractory epilepsy. METHODS: In this prospective multi-centre, open-label, add-on study, 33 children aged 4-16 years (median 8.5 years) with epilepsy refractory to at least two antiepileptic drugs were treated with levetiracetam in addition to their present treatment regimen with a follow-up of 26 weeks. The starting dose of 10 mg/kg/day was increased with 2-week steps of 10 mg/kg/day, if necessary, up to a maximum dose of 60 mg/kg/day. RESULTS: Retention rate was 69.7% after 26 weeks on a median levetiracetam dosage of 22 mg/kg/day. Four children dropped-out because levetiracetam was ineffective, four because seizure frequency increased and/or seizures became more severe, and two because they developed aggressive behaviour. Compared to their baseline seizure frequency, 13 children (39.4%) had a >50% seizure reduction 12 weeks after initiation of levetiracetam, and 17 children (51.5%) at 26 weeks. At 26 weeks, nine children (27.3%) had been seizure-free for at least the last 4 weeks, terminal remission ranged from 0 to 187 days (mean 46 days). Levetiracetam was effective in both partial and primary generalized seizures, but had most effect in partial seizures. Most reported side effects were hyperactivity (48.5%), somnolence (36.4%), irritability (33.3%) and aggressive behaviour (27.3%). Severity of most side effects was mild. Five children had a serious adverse event, which all concerned hospital admissions that were not related to levetiracetam use. CONCLUSION: Levetiracetam proved to be an effective and well-tolerated add-on treatment in this group of children with refractory epilepsy.

Validation of two prognostic models predicting outcome at two years after diagnosis in a new cohort of children with epilepsy: the Dutch Study of Epilepsy in Childhood.

PURPOSE: To validate two prognostic models for childhood-onset epilepsy designed to predict a terminal remission of <6 months at 2 years after diagnosis in children referred to the hospital. METHODS: A hospital-based cohort of children with newly diagnosed epilepsy was recruited and followed up for 2 years to validate previously developed models. One model was based on variables collected at intake, and the other was based on intake variables plus variables collected during the first 6 months of follow-up. The accuracy of both models was estimated by measuring the area under the receiver-operant-characteristic curves (ROC area). RESULTS: The ROC area of the model developed with intake variables was 0.69 [95% confidence interval (CI), 0.64-0.74] for the original cohort and 0.62 (95% CI, 0.55-0.69) for the validation cohort. The best combination of sensitivity and specificity for the original cohort was 61.6% and 69.1%, whereas it was 60.0% and 61.4% for the validation cohort. For the model with intake and 6-month variables combined, the ROC area was 0.78 (95% CI, 0.73-0.82) for the original cohort and 0.71 (95% CI, 0.64-0.78) for the validation cohort. The sensitivity and specificity were 72.6% and 73.1%, respectively, for the original cohort and 67.4% and 60.2%, respectively, for the validation cohort. CONCLUSIONS: Although both models predict outcome better than chance, they are insufficiently accurate to be of practical value. Both models performed marginally less well with the validation cohort than with the original cohort, but in both instances, the model based on intake and 6-month variables was more accurate.

Course and prognosis of childhood epilepsy: 5-year follow-up of the Dutch study of epilepsy in childhood.

Knowing the prognosis of epilepsy will undoubtedly influence the treatment strategy. This study aimed to define the prospects of newly diagnosed childhood epilepsy, assess the dynamics of its course, identify relevant variables and develop models to assess the individual prognosis. Four hundred and fifty-three children with newly diagnosed epilepsy were followed for 5 years. Terminal remission at 5 years (TR5) was compared with terminal remission at 2 years (TR2) and with the longest remission during follow-up. Variables defined at intake and at 6 months of follow-up were analysed for their prognostic relevance. In multivariate analyses, combinations of variables were tested to develop reliable models for the calculation of the individual prognosis. Data on treatment, course during follow-up and epilepsy syndromes were also studied. Three hundred and forty-five children (76%) had a TR5 >1 year, 290 (64%) >2 years and 65 (14%) had not had any seizure during the entire follow-up. Out of 108 children (24%) with TR5 <1 year, 27 were actually intractable at 5 years. Medication was started in 388 children (86%). In 227 of these (59%), anti-epileptic drugs (AEDs) could be withdrawn. A TR5 >1 year was attained by 46% on one AED, on the second AED by 19%, and by 9% on all additional AED regimes. Almost 60% of the children treated with a second or additional AED regime had a TR5 >1 year. Variables predicting the outcome at intake were aetiology, history of febrile seizures and age. For intake and 6-month variables combined, sex, aetiology, postictal signs, history of febrile seizures and TR at 6 months were significant. The model derived from intake variables only predicted TR5 <1 year correctly in 36% and TR5 >1 year in 85% (sensitivity 0.65, specificity 0.64). The corresponding values for the model derived from intake and 6-month variables were 43 and 88% (sensitivity 0.69, specificity 0.71). The course of the epilepsy was constantly favourable in 51%, steadily poor in 17%, improving in 25% and deteriorating in 6%. Intractability was in part only a temporary phenomenon. The outcome at 5 years in this cohort of children with newly diagnosed epilepsy was favourable in 76%; 64% were off medication at that time. Almost a third of the children had a fluctuating course; improvement was clearly more common than deterioration. After failure of the first AED, treatment can still be successful. Models predicting the outcome have fewer misclassifications when predicting a long terminal remission than when predicting continuing seizures.