Clinical evaluation and diagnosis of severe epilepsy syndromes of early childhood

A systematic review of electroencephalographic findings in Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is a severe form of childhood onset epileptic encephalopathy characterized by multiple drug-resistant seizures, cognitive impairment, and diffuse slow spike and wave (SSW), and generalized paroxysmal fast activity (GPFA) on electroencephalogram (EEG). Systematic review following the Preferred Reporting Items for Systematic Reviews and Meta Analysis (PRISMA) guidelines was done to investigate EEG findings in LGS. PubMed and MEDLINE were systematically searched for English-language studies published until15th may 2023. Original articles and research with patients between age group 1-30 years, and studies with description of EEG findings were included. Search identified 20 studies with 1167 patients. In this analysis 62.6 % of patients were male. The median age was 9.6 years. Etiology was structural abnormality in 42.6 %, genetic in 8.7 % but was unknown in 48.7%. Tonic seizures (74.5 %) were most frequent followed by atypical absences (44.3 %), myoclonic (39.2 %), generalized (38.5 %), atonic (34.8 %), epileptic spasm (15.9 %), focal (11.4 %) and non-convulsive status epilepticus (7.0 %). Out of 20 studies, only 15 studies mentioned GPFA in 46.6 % patients and SSW in 91.7 % patients. Unilateral and focal discharges were more common in patients with unilateral structural abnormalities. Seizure discharges on EEG longer than 10 second duration correlated with seizure diary counts. Combination of atonic, tonic, and atypical absence seizures correlated with SSW, and myoclonic seizures correlated with GPFA. EEG helps in diagnosis and prognosis of LGS. SSW is present in almost all EEG, and GPFA in 46.6 % patients. Longer duration of SSW discharges and disorganized background are associated with poor outcome.

Early Infantile Epileptic Encephalopathy related to NECAP1; clinical delineation of the disease and review

BACKGROUND

Epileptic encephalopathy (EE) refers to a heterogeneous group of epilepsy syndromes characterized by seizures as well as encephalopathies, leading to cognitive and behavioral disturbances. These conditions vary in their age of onset, their severity as well as their electroencephalographic patterns. While genetic factors are involved in approximately 40% of all epilepsy cases, they contribute to 80% of infantile epileptic encephalopathies (EIEE) with around 125 genes previously linked to this disease.

METHODS

Whole exome sequencing (WES) was performed in a 9-month-old Lebanese girl presenting with EIEE.

RESULTS

WES enabled the detection of a homozygous missense mutation in the NECAP1 gene (NM_015509.3: p.Glu8Lys) in the proband.

CONCLUSION

Here we report the first homozygous missense mutation in the NECAP1 gene in a 9-month-old girl presenting with EIEE. Our findings allow a better characterization of the NECAP1-linked disease and enable to broaden its clinical spectrum by including, in addition to EIEE, severe generalized hypotonia, poor feeding, developmental delay, severe microcephaly, delayed myelination, abnormalities of the corpus callosum, and eye abnormalities.

Genetic and Phenotype Analysis of a Chinese Cohort of Infants and Children With Epilepsy

Background: Epilepsy in childhood is a common and diverse neurological disorder. We conducted a genetic and phenotype analysis of a Chinese cohort of infants and children with epilepsy.

Methods: We conducted a pedigree analysis of 260 Chinese patients with epilepsy onset during infancy or childhood by whole exome sequencing (WES).

Results: Of the 260 probands analyzed, a genetic diagnosis was established in 135 patients. One-hundred eighty-eight phenotypes were detected in those 135 positive/likely positive patients, 106 patients had more than two phenotypes, and 67 patients had more than three phenotypes. A total of 142 variants of 81 genes were detected among the positive/likely positive patients. Among these 142 variants, of which 87 of 66 genes were novel.

Conclusion: Our findings extend the variant spectrum of genes related to epilepsy. Our results will be useful for genetic testing and counseling for patients with epilepsy.

Epileptic Encephalopathies

PURPOSE OF REVIEW

This article reviews the manifestations and treatment of the epileptic encephalopathies, which are a heterogeneous group of disorders characterized by both seizures and neurocognitive impairment.

RECENT FINDINGS

Next-generation (exome- and genome-based) sequencing technologies are revolutionizing the identification of single-gene causes of epileptic encephalopathy but have only had a modest impact on patient-specific treatment decisions. The treatment of most forms of epileptic encephalopathy remains a particularly challenging endeavor, with therapeutic decisions chiefly driven by the electroclinical syndrome classification. Most antiseizure drugs are ineffective in the treatment of these disorders, and treatments that are effective often entail significant risk and cost.

SUMMARY

The epileptic encephalopathies continue to pose a major challenge in diagnosis and treatment, with most patients experiencing very poor outcomes, although a significant minority of patients respond to, or are even cured by, specific therapies.

Ketogenic diet effects on 52 children with pharmacoresistant epileptic encephalopathy: A clinical prospective study

OBJECTIVE

To evaluate the clinical impact of ketogenic diet (KD) on children with pharmacoresistant epileptic encephalopathy.

METHODS

In all, 52 children with pharmacoresistant epileptic encephalopathy that diagnosed in our hospital from July 2012 to June 2015 were selected, including West syndrome 38 cases, Lennox-Gastaut Syndrome 7 cases, Doose Syndrome 1 case, and Dravet syndrome 6 cases, and the effect, compliance, adverse reactions, electroencephalogram (EEG), and cognitive function were analyzed. Modified Johns Hopkins protocol was used to initiate KD, and Engel scale was used to evaluate the effect, and evaluated the effect of KD on the cognition, language, and motor function.

RESULTS

At 12 weeks of KD treatment, the patients achieved I, II, III, and IV grade effect were accounted for 26.9% (14/52 cases), 17.3% (9/52 cases), 11.5% (6/52 cases), and 44.2% (23/52 cases), respectively, according to Engel scale. KD has different effect on different epileptic syndromes, best effect on Doose syndromes of 100%, and better effect on West syndrome with the effect rate of 57.9%, and the total effect number was 22 cases. The reduction of epileptiform discharges in the awake state before KD treatment was correlated with the seizure time after 3 months of KD treatment (r = .330, p = .017). The cognitive function of 23 patients was improved, 12 patients had language improvement, and the motor function was improved in 10 patients. In all, 23 patients had adverse reactions, and all patients were tolerated and improved.

CONCLUSION

KD has certain effect on children with pharmacoresistant epileptic encephalopathy, and it can reduce interictal epileptic discharge frequency, and improve the background rhythm of EEG. The reduction of epileptiform discharges in awake state is in favor of the reduction of seizures frequency, thus increasing the efficacy, and improve the cognitive function, language, and motor function to varying degrees, combined with less adverse reaction, which is worthy of clinical application.

Epileptic Encephalopathies-Clinical Syndromes and Pathophysiological Concepts

Epileptic encephalopathies account for a large proportion of the intractable early-onset epilepsies and are characterized by frequent seizures and poor developmental outcome. The epileptic encephalopathies can be loosely divided into two related groups of named syndromes. The first comprises epilepsies where continuous EEG changes directly result in cognitive and developmental dysfunction. The second includes patients where cognitive impairment is present at seizure onset and is due to the underlying etiology but the epileptic activity may then worsen the cognitive abilities over time. Recent, large-scale exome studies have begun to establish the genetic architecture of the epileptic encephalopathies, resulting in a re-consideration of the boundaries of these named syndromes. The emergence of this genetic architecture has lead to three main pathophysiological concepts to provide a mechanistic framework for these disorders. In this article, we will review the classic syndromes, the most significant genetic findings, and relate both to the pathophysiological understanding of epileptic encephalopathies.

Early-onset epileptic encephalopathies and the diagnostic approach to underlying causes

Early-onset epileptic encephalopathies are one of the most severe early onset epilepsies that can lead to progressive psychomotor impairment. These syndromes result from identifiable primary causes, such as structural, neurodegenerative, metabolic, or genetic defects, and an increasing number of novel genetic causes continue to be uncovered. A typical diagnostic approach includes documentation of anamnesis, determination of seizure semiology, electroencephalography, and neuroimaging. If primary biochemical investigations exclude precipitating conditions, a trial with the administration of a vitaminic compound (pyridoxine, pyridoxal-5-phosphate, or folinic acid) can then be initiated regardless of presumptive seizure causes. Patients with unclear etiologies should be considered for a further workup, which should include an evaluation for inherited metabolic defects and genetic analyses. Targeted next-generation sequencing panels showed a high diagnostic yield in patients with epileptic encephalopathy. Mutations associated with the emergence of epileptic encephalopathies can be identified in a targeted fashion by sequencing the most likely candidate genes. Next-generation sequencing technologies offer hope to a large number of patients with cryptogenic encephalopathies and will eventually lead to new therapeutic strategies and more favorable long-term outcomes.

A novel familial mutation in the PCSK1 gene that alters the oxyanion hole residue of proprotein convertase 1/3 and impairs its enzymatic activity

Four siblings presented with congenital diarrhea and various endocrinopathies. Exome sequencing and homozygosity mapping identified five regions, comprising 337 protein-coding genes that were shared by three affected siblings. Exome sequencing identified a novel homozygous N309K mutation in the proprotein convertase subtilisin/kexin type 1 (PCSK1) gene, encoding the neuroendocrine convertase 1 precursor (PC1/3) which was recently reported as a cause of Congenital Diarrhea Disorder (CDD). The PCSK1 mutation affected the oxyanion hole transition state-stabilizing amino acid within the active site, which is critical for appropriate proprotein maturation and enzyme activity. Unexpectedly, the N309K mutant protein exhibited normal, though slowed, prodomain removal and was secreted from both HEK293 and Neuro2A cells. However, the secreted enzyme showed no catalytic activity, and was not processed into the 66 kDa form. We conclude that the N309K enzyme is able to cleave its own propeptide but is catalytically inert against in trans substrates, and that this variant accounts for the enteric and systemic endocrinopathies seen in this large consanguineous kindred.

NECAP1 loss of function leads to a severe infantile epileptic encephalopathy

BACKGROUND

Epileptic encephalopathy is a broad clinical category that is highly heterogeneous genetically.

OBJECTIVE

To describe a multiplex extended consanguineous family that defines a molecularly novel subtype of early infantile epileptic encephalopathy.

METHODS

Autozygosity mapping and exome sequencing for the identification of the causal mutation. This was followed by expression analysis of the candidate gene.

RESULTS

In an extended multigenerational family with six affected individuals, a single novel disease locus was identified on chromosome 12p13.31-p13.2. Within that locus, the only deleterious novel exomic variant was a homozygous truncating mutation in NECAP1, encoding a clathrin-accessory protein. The mutation was confirmed to trigger nonsense-mediated decay. Consistent with previous reports, we show that NECAP1 is highly enriched in the central nervous system.

CONCLUSIONS

NECAP1 is known to regulate clathrin-mediated endocytosis in synapses. The mutation we report here links for the first time this trafficking pathway in early infantile epileptic encephalopathy.

Biallelic SZT2 mutations cause infantile encephalopathy with epilepsy and dysmorphic corpus callosum

Epileptic encephalopathies are genetically heterogeneous severe disorders in which epileptic activity contributes to neurological deterioration. We studied two unrelated children presenting with a distinctive early-onset epileptic encephalopathy characterized by refractory epilepsy and absent developmental milestones, as well as thick and short corpus callosum and persistent cavum septum pellucidum on brain MRI. Using whole-exome sequencing, we identified biallelic mutations in seizure threshold 2 (SZT2) in both affected children. The causative mutations include a homozygous nonsense mutation and a nonsense mutation together with an exonic splice-site mutation in a compound-heterozygous state. The latter mutation leads to exon skipping and premature termination of translation, as shown by RT-PCR in blood RNA of the affected boy. Thus, all three mutations are predicted to result in nonsense-mediated mRNA decay and/or premature protein truncation and thereby loss of SZT2 function. Although the molecular role of the peroxisomal protein SZT2 in neuronal excitability and brain development remains to be defined, Szt2 has been shown to influence seizure threshold and epileptogenesis in mice, consistent with our findings in humans. We conclude that mutations in SZT2 cause a severe type of autosomal-recessive infantile encephalopathy with intractable seizures and distinct neuroradiological anomalies.

Novel 9q34.11 gene deletions encompassing combinations of four Mendelian disease genes: STXBP1, SPTAN1, ENG, and TOR1A

PURPOSE

A number of genes in the 9q34.11 region may be haploinsufficient. However, studies analyzing genotype-phenotype correlations of deletions encompassing multiple dosage-sensitive genes in the region are lacking.

METHODS

We mapped breakpoints of 10 patients with 9q34.11 deletions using high-resolution 9q34-specific array comparative genomic hybridization (CGH) to determine deletion size and gene content.

RESULTS

The 9q34.11 deletions range in size from 67 kb to 2.8 Mb. Six patients exhibit intellectual disability and share a common deleted region including STXBP1; four manifest variable epilepsy. In five subjects, deletions include SPTAN1, previously associated with early infantile epileptic encephalopathy, infantile spasms, intellectual disability, and hypomyelination. In four patients, the deletion includes endoglin (ENG), causative of hereditary hemorrhagic telangiectasia. Finally, in four patients, deletions involve TOR1A, of which molecular defects lead to early-onset primary dystonia. Ninety-four other RefSeq genes also map to the genomic intervals investigated.

CONCLUSION

STXBP1 haploinsufficiency results in progressive encephalopathy characterized by intellectual disability and may be accompanied by epilepsy, movement disorders, and autism. We propose that 9q34.11 genomic deletions involving ENG, TOR1A, STXBP1, and SPTAN1 are responsible for multisystemic vascular dysplasia, early-onset primary dystonia, epilepsy, and intellectual disability, therefore revealing cis-genetic effects leading to complex phenotypes.

A genetic diagnostic approach to infantile epileptic encephalopathies

Epileptic encephalopathies are characterized by frequent severe seizures, and/or prominent interictal epileptiform discharges on the electroencephalogram, developmental delay or deterioration, and usually a poor prognosis. The epileptiform abnormalities themselves are believed to contribute to the progressive disturbance in cerebral function. Determining the underlying aetiology responsible for infantile epileptic encephalopathy is a clinical challenge worth undertaking to facilitate advice on the recurrence risk and to allow for the option of prenatal testing, as often this category of epilepsy is associated with devastating hardship for families. This review takes advantage of recently published studies that have identified new genes associated with epilepsy and focuses on known monogenic causes where detection is useful for the process of genetic counselling. Based on the review, we present a diagnostic work-up in order to triage specific genetic testing for infants presenting with an epileptic encephalopathy.

Molecular bases and clinical spectrum of early infantile epileptic encephalopathies

Epilepsy can be a challenging diagnosis to make in the neonatal and infantile periods. Seizures in this age group may be due to a serious underlying cause that results in an epileptic encephalopathy. Early infantile epileptic encephalopathy (EIEE) is a progressive neurologic condition that exhibits concomitant cognitive and motor impairment, and is often associated with severe intellectual disability. This condition belongs to the group of age-dependent epileptic encephalopathies, and thus the clinical and electro-encephalographic features change with age as the central nervous system evolves. The molecular bases and the clinical spectrum associated with the early infantile epileptic encephalopathies continue to expand as new genetic discoveries are made. This review will highlight the molecular etiologies of early infantile epileptic encephalopathy, and the clinical and electro-encephalographic changes that take place in these epileptic phenotypes as the brain develops.

Definition and natural history of Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is a rare epileptic encephalopathy with a peak age of onset of 3-5 years of age. Reported prevalence rates for LGS vary widely from 1-10% of all childhood epilepsies. Incidence rates are much lower. LGS is characterized by intractable, multiple, generalized seizure types and an interictal electroencephalogram showing bursts of slow spike-and-wave, paroxysmal bursts of generalized polyspikes, and a slow background. All patients have tonic seizures during sleep that may be subtle, and nearly all have treatment-resistant, lifelong epilepsy. Cognitive stagnation and behavioral problems are seen in almost all patients and lead to a life of dependency. The differential diagnosis includes other symptomatic generalized epilepsies and pseudo-Lennox syndrome. Misdiagnosis is common. Children and adults with LGS have an enormous impact on their families, and efforts to improve the quality of life for these patients are complex.

The evaluation of treatment-resistant epilepsy

An estimated 10% to 40% of children with epilepsy have treatment-resistant epilepsy. Persistent seizures have negative psychosocial, behavioral, cognitive, and financial consequences and are associated with an increased mortality rate. Accurate syndromic and etiologic diagnoses are of vital importance because they may guide medical and/or surgical decision making. Revisitation of the history to confirm the diagnosis of epilepsy and the appropriateness of medication trials to date is vital. Routine imaging should include structural magnetic resonance imaging (MRI) with an established epilepsy protocol. In the setting of a normal previous MRI, repeat imaging may be indicated and may be supplemented with other imaging modalities. The admission for prolonged inpatient video-encephalographic monitoring may lead to a revision of a pre-existing diagnosis. Laboratory evaluations should include genetic, metabolic, and infectious/inflammatory studies when indicated. In this review, we discuss the implication of seizure semiology and syndrome classification when searching for an underlying diagnosis in treatment-resistant epilepsy, and will review both basic and more advanced procedures/studies that may aid diagnosis.

Two novel mutations in SCN1A gene in Iranian patients with epilepsy

BACKGROUND AND AIMS

Epilepsy as a common chronic neurological disorder is characterized by recurrent unprovoked seizures. Febrile seizures are the most common type of epilepsy in infants and children. Our aim was the molecular analysis of SCN1A gene in affected Iranian patients with GEFS+ and Dravet syndrome diagnosed clinically to explain genotype-phenotype correlation and exact classification.

METHODS

The 34 unrelated Iranian families with epilepsy were selected and screened for SCN1A mutations by MLPA, ARMS, and PCR-RFLP confirmed by direct sequencing.

RESULTS

MLPA analysis showed normal patterns, but direct sequencing revealed that generally 20/34 (0.588) probands have common reported single nucleotide polymorphisms (SNPs) (p.A1067G; rs2298771) with allelic frequency as 0.706/0.294 in patients and 0.515/0.485 in control group, respectively, for A/G. No significant differences between groups were observed. Moreover, four novel allelic variants as missense substitutions included two new sequence variation (p.F412 I, p.Y1274N) and two previously reported mutations (p.R101G, p.S103G) that were detected in 4/34 probands but not in control groups and other healthy normal family members.

CONCLUSIONS

Clinical diagnosis could nearly establish the classification, but mutation screening helps clinicians to confirm their data. We found mutation in four probands and confirmed the net diagnosis. Our data suggest that the clinical symptom variations could be also explained, considering the role of modifier genes such as mitochondrial mutations or other genes responsible for drug metabolism pathways including multiple drug resistance family genes (ABCB1) or MTHFR.

Phospholipase C beta 1 deficiency is associated with early-onset epileptic encephalopathy

The epileptic encephalopathies of infancy and childhood are a collection of epilepsy disorders characterized by refractory, severe seizures and poor neurological outcome, in which the mechanism of disease is poorly understood. We report the clinical presentation and evolution of epileptic encephalopathy in a patient, associated with a loss-of-function mutation in the phospholipase C-β 1 gene. We ascertained a consanguineous family containing a male infant who presented with early-onset epileptic encephalopathy for detailed clinical phenotyping and molecular genetic investigation. In addition, a cohort of 12 consanguineous families of children with infantile spasms were analysed for linkage to the phospholipase C-β 1 gene locus. The male infant presented with tonic seizures in early infancy and subsequently developed infantile spasms. Over time, he developed drug-resistant epilepsy associated with severe neurological regression and failure to thrive. Molecular genetic investigation revealed a homozygous loss-of-function 0.5-Mb deletion, encompassing the promoter element and exons 1, 2 and 3 of phospholipase C-β 1 in the index case. Linkage to the phospholipase C-β 1 locus was excluded in the 12 other consanguineous families, consistent with genetic heterogeneity in this disorder. Although phospholipase C-β 1 deficiency has not previously been reported in humans, the Plcb1 homozygote knockout mouse displays early-onset severe tonic seizures and growth retardation, thus recapitulating the human phenotype. Phospholipase C-β 1 has important functions in both hippocampal muscarinic acetylcholine receptor signalling and in cortical development. Thus, the discovery of a phospholipase C-β 1 mutation allows us to propose a novel potential underlying mechanism in early-onset epileptic encephalopathy.