Epilepsy and inborn errors of metabolism in children

Epilepsy and Cognitive Impairment in Childhood and Adolescence: A Mini-Review

Managing epilepsy in people with an intellectual disability remains a therapeutic challenge and must take into account additional issues such as diagnostic difficulties and frequent drug resistance. Advances in genomic technologies improved our understanding of epilepsy and raised the possibility to develop patients-tailored treatments acting on the key molecular mechanisms involved in the development of the disease. In addition to conventional antiseizure medications (ASMs), ketogenic diet, hormone therapy and epilepsy surgery play an important role, especially in cases of drugresistance. This review aims to provide a comprehensive overview of the mainfactors influencing cognition in children and adolescents with epilepsy and the main therapeutic options available for the epilepsies associated with intellectual disability.

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.

EEG Pattern in Neonatal Maple Syrup Urine Disease: Description and Clinical Significance

Maple Syrup Urine Disease (MSUD) is a rare autosomal recessive disorder characterized by deficiency of branched-chain keto acid dehydrogenase complex, which is required to metabolize the three branched chain amino acids (BCAAs), leucine, isoleucine and valine. This metabolic dysfunction results in progressive encephalopathy manifesting with lethargy, vomiting, posturing and abnormal movements during the neonatal period in the classic form of the disease. If untreated, progressive brain damage causes coma, seizures and death usually within a few weeks. EEG is an essential investigation in a neonate with progressive encephalopathy and seizures. EEG abnormalities in neonatal encephalopathies due to inborn error of metabolism (IEM) are widely variable depending on the severity. Central comb-like rhythm is an EEG marker of neonatal MSUD in appropriate clinical context. This pattern should not be mistaken for epileptic abnormalities, sleep spindles or other similar nonspecific activities. We describe a patient with classic MSUD who presented with an EEG pattern of comb-like rhythm. Background abnormalities and epileptic discharges are common along comb-like rhythm in MSUD patients. EEG technologists and interpreters should be able to identify this pattern to support the early diagnosis and treatment of MSUD.

Metabolic Seizures

Metabolic diseases should always be considered when evaluating children presenting with seizures. This is because many metabolic disorders are potentially treatable and seizure control can be achieved when these diseases are appropriately treated. Seizures caused by underlying metabolic diseases (metabolic seizures) should be particularly considered in unexplained neonatal seizures, refractory seizures, seizures related to fasting or food intake, seizures associated with other systemic or neurologic features, parental consanguinity, and family history of epilepsy. Metabolic seizures can be caused by various amino acids metabolic disorders, disorders of energy metabolism, cofactor-related metabolic diseases, purine and pyrimidine metabolic diseases, congenital disorders of glycosylation, and lysosomal and peroxisomal disorders. Diagnosing metabolic seizures without delay is essential because the immediate initiation of appropriate therapy for many metabolic diseases can prevent or minimize complications.

Impact of predictive, preventive and precision medicine strategies in epilepsy

Over the last decade, advances in genetics, neuroimaging and EEG have enabled the aetiology of epilepsy to be identified earlier in the disease course than ever before. At the same time, progress in the study of experimental models of epilepsy has provided a better understanding of the mechanisms underlying the condition and has enabled the identification of therapies that target specific aetiologies. We are now witnessing the impact of these advances in our daily clinical practice. Thus, now is the time for a paradigm shift in epilepsy treatment from a reactive attitude, treating patients after the onset of epilepsy and the initiation of seizures, to a proactive attitude that is more broadly integrated into a 'P4 medicine' approach. This P4 approach, which is personalized, predictive, preventive and participatory, puts patients at the centre of their own care and, ultimately, aims to prevent the onset of epilepsy. This aim will be achieved by adapting epilepsy treatments not only to a given syndrome but also to a given patient and moving from the usual anti-seizure treatments to personalized treatments designed to target specific aetiologies. In this Review, we present the current state of this ongoing revolution, emphasizing the impact on clinical practice.

LC-MS/MS method for the differential diagnosis of treatable early onset inherited metabolic epilepsies

Rapid diagnosis and early specific treatment of metabolic epilepsies due to inborn errors of metabolism (IEMs) is crucial to avoid irreversible sequalae. Nowadays, besides the profile analysis of amino- and organic acids, a range of additional targeted assays is used for the selective screening of those diseases. This strategy can lead to long turn-around times, repeated sampling and diagnostic delays. To replace those individual targeted assays, we developed a new liquid chromatography mass spectrometry method (LC-MS/MS) for the differential diagnosis of inherited metabolic epilepsies that are potentially treatable. The method was developed to simultaneously quantify 12 metabolites (sulfocysteine, guanidinoacetate, creatine, pipecolic acid, Δ¹ -piperideine-6-carboxylate (P6C), proline, Δ¹ -pyrroline-5-carboxylate (P5C), and the B₆ -vitamers) enabling the diagnosis of nine different treatable IEMs presenting primarily with early-onset epilepsy. Plasma and urine samples were mixed with internal standards, precipitated and the supernatants were analyzed by LC-MS/MS. In comparison with previous assays, no derivatization of the metabolites is necessary for analysis. This LC-MS method was validated for quantitative results for all metabolites except P6C and P5C for which semiquantitative results were obtained due to the absence of commercially available standards. Coefficients of variation for all analytes were below 15% and recovery rates range between 80% and 120%. Analysis of patient samples with known IEMs demonstrated the diagnostic value of the method. The presented assay covers a selected panel of biochemical markers, improves the efficiency in the laboratory, and potentially leads to faster diagnoses and earlier treatment avoiding irreversible damage in patients affected with IEMs.

The highly efficient powerhouse in the Wistar audiogenic rat, an epileptic rat strain

The Wistar audiogenic rat (WAR) is an animal model of tonic-clonic epileptic seizures, developed after genetic selection by sister × brother inbreeding of Wistar rats susceptible to sound stimuli. Although metabolic changes have been described in this strain, nothing is known about its mitochondrial metabolism. Here, we addressed mitochondrial aspects of oxidative phosphorylation, oxidative stress, biogenesis, and dynamics in liver, skeletal muscle, and heart of male WARs and correlating them with physiological aspects of body metabolism. The results showed higher mitochondrial content, respiration rates in phosphorylation and noncoupled states, and H₂O₂ production in WARs. Liver presented higher content of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α) and mammalian target of rapamycin, proteins related to mitochondrial biogenesis. In agreement, isolated liver mitochondria from WARs showed higher respiration rates in phosphorylation state and ADP-to-O ratio, as well as higher content of proteins related to electron transport chain ATP synthase, TCA cycle, and mitochondrial fusion and fission compared with their Wistar counterparts. Mitochondria with higher area and perimeter and more variable shapes were found in liver and soleus from WARs in addition to lower reduced-to-oxidized glutathione ratio. In vivo, WARs demonstrated lower body mass and energy expenditure but higher food and water intake and amino acid oxidation. When exposed to a running test, WARs reached higher speed and resisted for a longer time and distance than their Wistar controls. In conclusion, the WAR strain has mitochondrial changes in liver, skeletal muscle, and heart that improve its mitochondrial capacity of ATP production, making it an excellent rat model to study PGC1α overexpression and mitochondrial function in different physiological conditions or facing pathological challenges.

Inborn Errors of Metabolism with Seizures: Defects of Glycine and Serine Metabolism and Cofactor-Related Disorders

Inborn errors of metabolism (IEM) are relatively uncommon causes for seizures in children; however, they should be considered in the differential diagnosis because several IEM are potentially treatable and seizures can be resolved if appropriate treatment is initiated. Clues from clinical presentation, physical examination, laboratory tests, and brain imaging can raise the possibility of IEM. Several IEM can present with seizures, either as the main presenting finding or as a part of a more complex phenotype. These include cofactor-related disorders, glycine and serine metabolism defects, and other disorders.

Inborn Errors of Metabolism Overview: Pathophysiology, Manifestations, Evaluation, and Management

The specialty of inherited metabolic disease is at the forefront of progress in medicine, with new methods in metabolomics and genomics identifying the molecular basis for a growing number of conditions and syndromes. This review presents an updated pathophysiologic classification of inborn errors of metabolism and a method of clinical screening in neonates, late-onset emergencies, neurologic deterioration, and other common clinical scenarios. When and how to investigate a metabolic disorder is presented to encourage physicians to use sophisticated biochemical investigations and not miss a treatable disorder.

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.

Inborn errors of metabolism

Inborn errors of metabolism (IEM) are individually rare but collectively common. Approximately 25% of IEMs can have manifestations in the neonatal period. Neonates with IEM are usually healthy at birth; however, in hours to days after birth they can develop nonspecific signs that are common to several other neonatal conditions. Therefore, maintaining a high index of suspicion is extremely important for early diagnosis and the institution of appropriate therapy, which are mandatory to prevent death and ameliorate complications from many IEMs.

Refractory epilepsy in children

Refractory epilepsy, estimated to affect 10-20% children with epilepsy, can have profound effect on the education, social and cognitive functioning and recreational activities of the child. The definitions are still evolving. A detailed clinical evaluation may reveal an accurate syndromic and etiological diagnosis. The recent advances in neuroimaging and electrophysiology have revolutionized the management of children with refractory epilepsy and supplement the clinical evaluation. Genetic and metabolic evaluation may be indicated in selected cases. The rational use of anti-epileptic drugs, epilepsy surgery and dietary therapies are the mainstay in the management. Various experimental treatment options and pharmacogenetics offer hope for future.

The use of magnetic resonance spectroscopy in the evaluation of epilepsy

Magnetic resonance spectroscopy (MRS) is indicated in the imaging protocol of the patient with epilepsy to screen for metabolic derangements such as inborn errors of metabolism and to characterize masses that may be equivocal on conventional magnetic resonance imaging for dysplasia versus neoplasia. Single-voxel MRS with echo time of 35 milliseconds may be used for this purpose as a quick screening tool in the epilepsy imaging protocol. MRS is useful in the evaluation of both focal and generalized epilepsy.

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.

Metabolic epilepsy: an update

Inborn errors of metabolism comprise a large class of genetic diseases involving disorders of metabolism. Presentation is usually in the neonatal period or infancy but can occur at any time, even in adulthood. Seizures are frequent symptom in inborn errors of metabolism, with no specific seizure types or EEG signatures. The diagnosis of a genetic defect or an inborn error of metabolism often results in requests for a vast array of biochemical and molecular tests leading to an expensive workup. However a specific diagnosis of metabolic disorders in epileptic patients may provide the possibility of specific treatments that can improve seizures. In a few metabolic diseases, epilepsy responds to specific treatments based on diet or supplementation of cofactors (vitamin-responsive epilepsies), but for most of them specific treatment is unfortunately not available, and conventional antiepileptic drugs must be used, often with no satisfactory success. In this review we present an overview of metabolic epilepsies based on various criteria such as treatability, age of onset, seizure type, and pathogenetic background.

Manifestations and treatment of epilepsy in children with neurometabolic disorders: a series from Jordan

PURPOSE

To examine the characteristics of epilepsy in children with neurometabolic disorders to reveal co morbidities and optimal treatment.

METHODS

We retrospectively reviewed the files of children diagnosed with a neurometabolic disorder and treated at Jordan University Hospital between 2001 and 2012. We examined the incidence, age at onset, clinical characteristics, and medical control of epilepsy.

RESULTS

Cases treated (40 boys, 30 girls) included the different categories of neurometabolic diseases. Twenty-nine patients (41.4%) were also diagnosed with epilepsy, with age at seizure onset ranging from 3 days to 7 years. All types of seizures were reported, but generalized tonic-clonic and mixed types were most common (16/29 patients, 55.2%). Patients were on either a single antiepileptic drug (16/29, 55.2%) or multiple drugs (13/29, 44.7%), and most drugs prescribed were older generation anticonvulsants. Complete seizure control was achieved in 19/29 patients (65.5%), partial control in 7/29 (24.1%), and poor or no control in 3/29 (10.3%). EEG recordings were missing from the medical files of 10/29 patients. The first EEG revealed epileptiform activity in 12/19 patients (63.2%) and was normal in 7/19 patients (36.8%).

CONCLUSIONS

Epilepsy was diagnosed in about half of pediatric neurometabolic disease patients, with the majority of seizure cases well controlled.

Neurodegenerative disorders and metabolic disease

Most genetic causes of neurodegenerative disorders in childhood are due to neurometabolic disease. There are over 200 disorders, including aminoacidopathies, creatine disorders, mitochondrial cytopathies, peroxisomal disorders and lysosomal storage disorders. However, diagnosis can pose a challenge to the clinician when patients present with non-specific problems like epilepsy, developmental delay, autism, dystonia and ataxia. The variety of specialist tests involved can also be daunting. This review aims to give a practical approach to the investigation and diagnosis of neurometabolic disease from the neonatal period to late childhood while prioritising disorders where there are therapeutic options. In particular, patients who have a complex clinical picture of several neurological and non-neurological features should be investigated.

Metabolic diagnostic work-up in chronic conditions

Neurological symptoms are very frequent in inborn errors of metabolism. This chapter presents a general approach to investigate inborn errors of metabolism in chronic neurological conditions. A diagnostic work-up has been designed to evaluate progressive neurological conditions with motor, cognitive, and/or behavioral signs in early infancy, late infancy to early childhood, and late childhood to adolescence. Inborn errors of metabolism associated with peripheral neuropathies, microcephaly, or macrocephaly are also reviewed.

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.

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.

Metabolic and monogenic causes of seizures in neonates and young infants

Seizures in neonates or young infants present a frequent diagnostic challenge. After exclusion of acquired causes, disturbances of the internal homeostasis and brain malformations, the physician must evaluate for inborn errors of metabolism and for other non-malformative genetic disorders as the cause of seizures. The metabolic causes can be categorized into disorders of neurotransmitter metabolism, disorders of energy production, and synthetic or catabolic disorders associated with brain malformation, dysfunction and degeneration. Other genetic conditions involve channelopathies, and disorders resulting in abnormal growth, differentiation and formation of neuronal populations. These conditions are important given their potential for treatment and the risk for recurrence in the family. In this paper, we will succinctly review the metabolic and genetic non-malformative causes of seizures in neonates and infants less than 6 months of age. We will then provide differential diagnostic clues and a practical paradigm for their evaluation.

Investigation of the child with an acute metabolic disorder

Inherited biochemical defects may present with acute life-threatening illness with a high mortality and morbidity. Some are treatable and have a good outcome with early appropriate intervention. However, because of their rarity, diagnosis is often delayed; they are not considered or investigated appropriately. This is especially likely in those presenting in previously healthy adults. The collection of acute samples is crucial. There are numerous disorders, and front-line tests must cast a wide net. A small core of emergency tests generally indicates which metabolic pathway is defective and provides a working diagnosis and basis for treatment. Later confirmation and identification of the precise defect are essential for long-term management and for genetic counselling and prenatal diagnosis of future pregnancies. An escalating number of specialist tests and mutation analyses are undertaken by metabolic laboratories worldwide, but they are not widely available, are expensive, and must be requested selectively. Guidelines are presented here for the front-line investigation of acutely ill children with hypoglycaemia, metabolic acidosis, encephalopathy and intractable seizures, and for a dying child with a suspected, undiagnosed, inherited metabolic defect. With modification, these are also applicable to adults with a metabolic defect. In order to guide further investigation, selected disorders are described briefly along with their diagnostic work-up. Information about sample collection and processing is provided.