Early onset epilepsy and inherited metabolic disorders: diagnosis and management

Congenital disorders of glycosylation and infantile epilepsy

Congenital disorders of glycosylation (CDG) are a group of rare inherited metabolic disorders caused by defects in various defects of protein or lipid glycosylation pathways. The symptoms and signs of CDG usually develop in infancy. Epilepsy is commonly observed in CDG individuals and is often a presenting symptom. These epilepsies can present across the lifespan, share features of refractoriness to antiseizure medications, and are often associated with comorbid developmental delay, psychomotor regression, intellectual disability, and behavioral problems. In this review, we discuss CDG and infantile epilepsy, focusing on an overview of clinical manifestations and electroencephalographic features. Finally, we propose a tiered approach that will permit a clinician to systematically investigate and identify CDG earlier, and furthermore, to provide genetic counseling for the family.

Metabolic Epilepsy

Inborn errors of metabolism have been considered as an infrequent cause of epilepsy. Improvement in diagnostics has improved the detection of a metabolic basis of recurrent seizures in neonates and children. The term 'metabolic epilepsy' is used to suggest inherited metabolic disorders with predominant epileptic manifestations as well as those where epilepsy is part of the overall neurological phenotype. Several of these disorders are treatable, and the physician should bear in mind the classical ages of presentation. As there are no specific clinical or electrographic features suggestive of metabolic epilepsies, an early suspicion is based on clinical and laboratory clues. Fortunately, with the advancement of gene sequencing technology, a diagnosis of these rare conditions is more straightforward and may not require invasive procedures such as biopsies, multiple metabolic stress-induced testing for abnormalities, and cerebrospinal fluid analysis. A gene panel may suffice in most cases and can be done from a blood sample. In many countries, many treatable metabolic disorders are now part of the neonatal screen. Early diagnosis and treatment of these disorders can result in the prevention of a full-scale metabolic crisis and improvement of neurological outcomes. Long-term neurological outcomes are variable and additional therapies may be required.

Dysbiosis of the intestinal microbiome as a component of pathophysiology in the inborn errors of metabolism

Inborn errors of metabolism (IEMs) represent monogenic disorders in which specific enzyme deficiencies, or a group of enzyme deficiencies (e.g., peroxisomal biogenesis disorders) result in either toxic accumulation of metabolic intermediates or deficiency in the production of key end-products (e.g., low cholesterol in Smith-Lemli-Opitz syndrome (Gedam et al., 2012 [1]); low creatine in guanidinoacetic acid methyltransferase deficiency (Stromberger, 2003 [2])). Some IEMs can be effectively treated by dietary restrictions (e.g., phenylketonuria (PKU), maple syrup urine disease (MSUD)), and/or dietary intervention to remove offending compounds (e.g., acylcarnitine excretion with the oral intake of l-carnitine in the disorders of fatty acid oxidation). While the IEMs are predominantly monogenic disorders, their phenotypic presentation is complex and pleiotropic, impacting multiple physiological systems (hepatic and neurological function, renal and musculoskeletal impairment, cardiovascular and pulmonary activity, etc.). The metabolic dysfunction induced by the IEMs, as well as the dietary interventions used to treat them, are predicted to impact the gut microbiome in patients, and it is highly likely that microbiome dysbiosis leads to further exacerbation of the clinical phenotype. That said, only recently has the gut microbiome been considered as a potential pathomechanistic consideration in the IEMs. In this review, we overview the function of the gut-brain axis, the crosstalk between these compartments, and the expanding reports of dysbiosis in the IEMs recently reported. The potential use of pre- and probiotics to improve clinical outcomes in IEMs is also highlighted.

Inborn Errors of Metabolism and Epilepsy: Current Understanding, Diagnosis, and Treatment Approaches

Inborn errors of metabolism (IEM) are a rare cause of epilepsy, but seizures and epilepsy are frequently encountered in patients with IEM. Since these disorders are related to inherited enzyme deficiencies with resulting effects on metabolic/biochemical pathways, the term “metabolic epilepsy” can be used to include these conditions. These epilepsies can present across the life span, and share features of refractoriness to anti-epileptic drugs, and are often associated with co-morbid developmental delay/regression, intellectual, and behavioral impairments. Some of these disorders are amenable to specific treatment interventions; hence timely and appropriate diagnosis is critical to improve outcomes. In this review, we discuss those disorders in which epilepsy is a dominant feature and present an approach to the clinical recognition, diagnosis, and management of these disorders, with a greater focus on primarily treatable conditions. Finally, we propose a tiered approach that will permit a clinician to systematically investigate, identify, and treat these rare disorders.

Epileptic Encephalopathy in Childhood: A Stepwise Approach for Identification of Underlying Genetic Causes

Epilepsy is one of the most common neurological disorders in childhood. Epilepsy associated with global developmental delay and cognitive dysfunction is defined as epileptic encephalopathy. Certain inherited metabolic disorders presenting with epileptic encephalopathy can be treated with disease specific diet, vitamin, amino acid or cofactor supplementations. In those disorders, disease specific therapy is successful to achieve good seizure control and improve long-term neurodevelopmental outcome. For this reason, intractable epilepsy with global developmental delay or history of developmental regression warrants detailed metabolic investigations for the possibility of an underlying treatable inherited metabolic disorder, which should be undertaken as first line investigations. An underlying genetic etiology in epileptic encephalopathy has been supported by recent studies such as array comparative genomic hybridization, targeted next generation sequencing panels, whole exome and whole genome sequencing. These studies report a diagnostic yield up to 70%, depending on the applied genetic testing as well as number of patients enrolled. In patients with epileptic encephalopathy, a stepwise approach for diagnostic work-up will help to diagnose treatable inherited metabolic disorders quickly. Application of detailed genetic investigations such as targeted next generation sequencing as second line and whole exome sequencing as third line testing will diagnose underlying genetic disease which will help for genetic counseling as well as guide for prenatal diagnosis. Knowledge of underlying genetic cause will provide novel insights into the pathogenesis of epileptic encephalopathy and pave the ground towards the development of targeted neuroprotective treatment strategies to improve the health outcome of children with epileptic encephalopathy.

W44X mutation in the WWOX gene causes intractable seizures and developmental delay: a case report

Background

WW domain containing oxidoreductase (WWOX) gene was cloned in 2000; alteration has been seen in many cancer cells. It acts as a tumor suppresser by blocking cell growth and causing apoptosis. WWOX protein showed different expression of mice brain and spinal cord, for which deletion causes seizure and early death.

Case presentation

Clinical and molecular characteristics of a consanguineous family show a homozygous mutation of WWOX gene at specific bases, causing a debilitating syndrome characterized by growth retardation, intractable epilepsy, intellectual disability, and early death.

Using Whole Exome Sequencing (WES), a novel homozygous mutation in the WWOX gene is identified in a consanguineous Arab family from Qatar with two daughters who presented with intractable seizure and developmental delay.

Conclusion

The study presents the importance of human WWOX gene for brain development and the association between gene mutation and epileptic encephalopathy. It also highlights the power of WES particularly in clinically challenging cases.

Screening of inherited metabolic abnormalities in 56 children with intractable epilepsy

Epilepsy is a common children's neural disease that is largely controlled by anti-epileptic drugs. Nevertheless, children experience repeated attacks that develop into intractable epilepsy (IE). The aim of the present study was to examine the inherited metabolic abnormalities in children with IE to provide early etiological and symptomatic treatment. Urine and blood samples of 56 children with IE served as the experimental group and 56 cases of children with IE, who were successfully treated served as the control group, and analyzed by gas chromatography-mass spectrometry and tandem mass spectrometry for the metabolic screening of amino, organic, and fatty acids. Urine routine, hepatic function, blood biochemistry, imageology of encephalon and brain stem-evoked potential (auditory and optical) were also examined. Of the 27 IE children confirmed as abnormal in urine and blood screening, there were 19 cases (70.3%) of hypoevolutism or retrogression of intelligence and motor function, 15 cases (55.5%) of brain stem-evoked potential and of encephalic computed tomography (CT) or magnetic resonance imaging (MRI) abnormality, 6 cases (22.2%) of abnormal family history and of abnormal blood biochemistry and blood gas analysis, and 5 cases (18.5%) with skin change and of abnormal hepatic function. Of the 27 cases, 11 cases (19.6%) were diagnosed with inherited metabolic diseases. Among the children in the control group, 3 cases showed abnormal urine test results, one of which had family history, one had hypoevolutism or retrogression of intelligence and motor function, one had brain stem-evoked potential and encephalic CT or MRI abnormality, while two of the 3 cases had inherited metabolic abnormalities. The correlation analysis revealed that abnormal urine test was significantly correlated with inherited metabolic abnormalities (P<0.05). Of the 56 IE patients, 25 cases (44.6%) were identified as abnormal under urine screening, and of the 25 cases, 6 cases had simple generalized seizure (24.0%), 5 cases had simple partial seizure (20.0%), 2 cases had multiple types of seizure (8.0%), and 12 cases had infantile spasms (48.0%). Six cases in the control group showed an abnormal urine test, with 3 cases of simple generalized seizure, 2 cases of simple partial seizure and 1 case of multiple types of seizure. The abnormal urine in infantile spasms was often the risk factor of IE. A total of 46 IE children underwent blood screening and 13 cases were diagnosed as abnormal. In conclusion, inherited metabolic abnormality was a common influential factor in the pathogenesis of IE, especially in infantile spasms. Screening of inborn metabolic abnormality in children with IE should be conducted as early as possible, to achieve early treatment and improve their prognosis.

Diagnostic Approach to Genetic Causes of Early-Onset Epileptic Encephalopathy

Epileptic encephalopathies are characterized by recurrent clinical seizures and prominent interictal epileptiform discharges seen during the early infantile period. Although epileptic encephalopathies are mostly associated with structural brain defects and inherited metabolic disorders, pathogenic gene mutations may also be involved in the development of epileptic encephalopathies even when no clear genetic inheritance patterns or consanguinity exist. The most common epileptic encephalopathies are Ohtahara syndrome, early myoclonic encephalopathy, epilepsy of infancy with migrating focal seizures, West syndrome and Dravet syndrome, which are usually unresponsive to traditional antiepileptic medication. Many of the diagnoses describe the phenotype of these electroclinical syndromes, but not the underlying causes. To date, approximately 265 genes have been defined in epilepsy and several genes including STXBP1, ARX, SLC25A22, KCNQ2, CDKL5, SCN1A, and PCDH19 have been found to be associated with early-onset epileptic encephalopathies. In this review, we aimed to present a diagnostic approach to primary genetic causes of early-onset epileptic encephalopathies.

Severe infantile epileptic encephalopathy due to mutations in PLCB1: expansion of the genotypic and phenotypic disease spectrum

Homozygous deletions of chromosome 20p12.3, disrupting the promoter region and first three coding exons of the phospholipase C β1 gene (PLCB1), have previously been described in two reports of early infantile epileptic encephalopathy (EIEE). Both children were born to consanguineous parents, one presented with infantile spasms, the other with migrating partial seizures of infancy. We describe an infant presenting with severe intractable epilepsy (without a specific EIEE electroclinical syndrome diagnosis) and neurodevelopmental delay associated with compound heterozygous mutations in PLCB1. A case note review and molecular genetic investigations were performed for a child, approximately 10 months of age, admitted to Johns Hopkins University Hospital for developmental delay and new-onset seizures. The patient presented at 6 months of age with developmental delay, followed by the onset of intractable, focal, and generalized seizures associated with developmental regression from 10 months of age. Presently, at 2 years of age, the child has severe motor and cognitive delays. Diagnostic microarray revealed a heterozygous 476kb deletion of 20p12.3 (encompassing PLCB1), which was also detected in the mother. The genomic breakpoints for the heterozygous deletion were determined. In order to investigate the presence of a second PLCB1 mutation, direct Sanger sequencing of the coding region and flanking intronic regions was undertaken, revealing a novel heterozygous intron 1 splice site variant (c.99+1G>A) in both the index individual and the father. Advances in molecular genetic testing have greatly improved diagnostic rates in EIEE, and this report further confirms the important role of microarray investigation in this group of disorders. PLCB1-EIEE is now reported in a number of different EIEE phenotypes and our report provides further evidence for phenotypic pleiotropy encountered in early infantile epilepsy syndromes.

Neonatal seizures: aetiology by means of a standardized work-up

Neonatal seizures are an alarming symptom and are frequent in neonates. It is important to find the cause of neonatal seizures to start a specific treatment and to give a meaningful prognosis. The aim of this study is to investigate the incidence of different aetiologies of neonatal seizures in our hospital by a specific work-up.

METHODS

All full-term born neonates from January 2002 till September 2009 with neonatal seizures, admitted to our neonatal intensive care unit were included (n = 221). Aetiology was investigated by means of a standardized aetiologic work-up.

RESULTS

The frequencies of aetiologies of neonatal seizures were: hypoxic-ischemic encephalopathy (HIE) (n = 119; 53.9%), metabolic or electrolyte disorders (n = 24; 10.9%), intracranial hemorrhage (n = 20; 9.0%), ischemic infarction (n = 16; 7.2%), intracranial infections (n = 14; 6.3%), congenital malformations of the central nervous system (n = 7; 3.2%), inborn errors of metabolism (n = 5; 2.3%), epileptic syndromes (n = 1; 0.5%), HIE + hypoglycemia (n = 4; 1.8%), HIE + intracranial hemorrhage (n = 3; 1.4%), HIE + ischemic infarction (n = 1; 0.5%), ischemic infarction + intracranial hemorrhage (n = 1; 0.5%), idiopathic (n = 4, 1.8%), intoxications (n = 1; 0.5%) and unknown (n = 1; 0.5%).

CONCLUSION

Our work-up is a practical tool to find the aetiology of neonatal seizures.

Who receives home-based perinatal palliative care: experience from Poland

Context. The current literature suggests that perinatal palliative care (PPC) programs should be comprehensive, initiated early, and integrative. So far there have been very few publications on the subject of home-based PC of newborns and neonates. Most publications focus on hospital-based care, mainly in the neonatal intensive care units. Objective. To describe the neonates and infants who received home-based palliative care in Lodz Region between 2005 and 2011. Methods. A retrospective review of medical records. Results. 53 neonates and infants were admitted to a home hospice in Lodz Region between 2005 and 2011. In general, they are a growing group of patients referred to palliative care. Congenital diseases (41%) were the primary diagnoses; out of 53 patients 16 died, 20 were discharged home, and 17 stayed under hospice care until 2011. The most common cause of death (56%) was cardiac insufficiency. Neurological symptoms (72%) and dysphagia (58%) were the most common clinical problems. The majority of children (45%) had a feeding tube inserted and were oxygen dependent (45%); 39 families received psychological care and 31 social supports. Conclusions. For terminally ill neonates and infants, perinatal palliative care is an option which improves the quality of their lives and provides the family with an opportunity to say goodbye.

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.

From genetics to genomics of epilepsy

The introduction of DNA microarrays and DNA sequencing technologies in medical genetics and diagnostics has been a challenge that has significantly transformed medical practice and patient management. Because of the great advancements in molecular genetics and the development of simple laboratory technology to identify the mutations in the causative genes, also the diagnostic approach to epilepsy has significantly changed. However, the clinical use of molecular cytogenetics and high-throughput DNA sequencing technologies, which are able to test an entire genome for genetic variants that are associated with the disease, is preparing a further revolution in the near future. Molecular Karyotype and Next-Generation Sequencing have the potential to identify causative genes or loci also in sporadic or non-familial epilepsy cases and may well represent the transition from a genetic to a genomic approach to epilepsy.

A diagnostic algorithm for the evaluation of early onset genetic-metabolic epileptic encephalopathies

Early onset epileptic encephalopathies represent a struggling challenge in neurological clinical practice, mostly in infants and very young children, partly due to an unclear and still debated cathegorization. In this scenario genetic and metabolic epileptic encephalopathies play a central role, with new entries still needing an arrangement. In this Paper we present a brief overview on genes, metabolic disorders and syndromes picturing the pathogenesis of genetic and metabolic epileptic encephalopathies with onset under one year of age. These forms will be classified, according to a combined clinical and genetic-metabolic criterion, into two main groups including seizures as prominent/unique symptom and seizures associated with a syndromic phenotype. Starting from this classification we suggest a possible simplified diagnostic algorithm, discussing main decision making nodes in practical patients management. The aim of the proposed algorithm is to guide through metabolic and molecular-genetic work up and to clarify "where" and "what" to search in biochemical, electroencephalographic and neuroimaging investigations.

Amplitude-integrated electroencephalography in newborns with inborn errors of metabolism

BACKGROUND

The utility of amplitude-integrated electroencephalography (aEEG) monitoring has been established for patients with neonatal hypoxic-ischemic encephalopathy.

OBJECTIVE

To evaluate the role of aEEG in the diagnostic process and treatment of patients with encephalopathy due to inborn errors of metabolism.

METHODS

Cases collected through an international registry were divided into 5 groups of metabolic disorders. Common aEEG features were sought for each group.

RESULTS

In total, 21/30 (70%) cases had abnormal aEEG background patterns, 18/30 (60%) showed seizure activity. Patients with disorders of energy metabolism, hyperammonemia, and organic/amino acidopathies often showed marked aEEG depression with seizure activity. In contrast, aEEGs of patients with peroxisomal disorders did not show major background abnormalities but seizures were present in 5/6 subjects. We report two features of interest: firstly, two tracings displayed an unusual upward shift of the lower aEEG amplitude margin. Secondly, aEEGs of infants with non-ketotic hyperglycinemia showed a pattern we refer to as 'high-frequency burst-suppression pattern'.

CONCLUSIONS

aEEG in patients with inborn errors of metabolism frequently reveals abnormalities and assists clinicians in the clinical assessment, management and monitoring of these patients.

Genes of early-onset epileptic encephalopathies: from genotype to phenotype

Early-onset epileptic encephalopathies are severe disorders in which cognitive, sensory, and motor development is impaired by recurrent clinical seizures or prominent interictal epileptiform discharges during the neonatal or early infantile periods. They include Ohtahara syndrome, early myoclonic epileptic encephalopathy, West syndrome, Dravet syndrome, and other diseases, e.g., X-linked myoclonic seizures, spasticity and intellectual disability syndrome, idiopathic infantile epileptic-dyskinetic encephalopathy, epilepsy and mental retardation limited to females, and severe infantile multifocal epilepsy. We summarize recent updates on the genes and related clinical syndromes involved in the pathogenesis of early-onset epileptic encephalopathies: Aristaless-related homeobox (ARX), cyclin-dependent kinase-like 5 (CDKL5), syntaxin-binding protein 1 (STXBP1), solute carrier family 25 member 22 (SLC25A22), nonerythrocytic α-spectrin-1 (SPTAN1), phospholipase Cβ1 (PLCβ1), membrane-associated guanylate kinase inverted-2 (MAGI2), polynucleotide kinase 3'-phosphatase (PNKP), sodium channel neuronal type 1α subunit (SCN1A), protocadherin 19 (PCDH19), and pyridoxamine 5-prime-phosphate oxidase (PNPO).