Epilepsy and inborn errors of metabolism in adults: a diagnostic approach

How to detect late-onset inborn errors of metabolism in patients with movement disorders - A modern diagnostic approach

We propose a modern approach to assist clinicians to recognize and diagnose inborn errors of metabolism (IEMs) in adolescents and adults that present with a movement disorder. IEMs presenting in adults are still largely unexplored. These disorders receive little attention in neurological training and daily practice, and are considered complicated by many neurologists. Adult-onset presentations of IEMs differ from childhood-onset phenotypes, which may lead to considerable diagnostic delay. The identification of adult-onset phenotypes at the earliest stage of the disease is important, since early treatment may prevent or lessen further brain damage. Our approach is based on a systematic review of all papers that concerned movement disorders due to an IEM in patients of 16 years or older. Detailed clinical phenotyping is the diagnostic cornerstone of the approach. An underlying IEM should be suspected in particular in patients with more than one movement disorder, or in patients with additional neurological, psychiatric, or systemic manifestations. As IEMs are all genetic disorders, we recommend next-generation sequencing (NGS) as the first diagnostic approach to confirm an IEM. Biochemical tests remain the first choice in acute-onset or treatable IEMs that require rapid diagnosis, or to confirm the metabolic diagnosis after NGS results. With the use of careful and systematic clinical phenotyping combined with novel diagnostic approaches such as NGS, the diagnostic yield of late-onset IEMs will increase, in particular in patients with mild or unusual phenotypes.

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.

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.

Natural history of succinic semialdehyde dehydrogenase deficiency through adulthood

OBJECTIVE

The natural history of succinic semialdehyde dehydrogenase (SSADH) deficiency in adulthood is unknown; we elucidate the clinical manifestations of the disease later in life.

METHODS

A 63-year-old man with long-standing intellectual disability was diagnosed with SSADH deficiency following hospitalization for progressive decline, escalating seizures, and prolonged periods of altered consciousness. We present a detailed review of his clinical course and reviewed our SSADH deficiency database adult cohort to derive natural history information.

RESULTS

Of 95 patients in the database for whom age at diagnosis is recorded, there are 40 individuals currently aged 18 years or older. Only 3 patients were diagnosed after age 18 years. Of 25 adults for whom data are available after age 18, 60% have a history of epilepsy. Predominant seizure types are generalized tonic-clonic, absence, and myoclonic. EEGs showed background slowing or generalized epileptiform discharges in two-thirds of adults for whom EEG data were collected. History of psychiatric symptoms was prominent, with frequent anxiety, sleep disturbances, and obsessive-compulsive disorder.

CONCLUSIONS

We identified patients older than 18 years with SSADH deficiency in our database following identification and review of a patient diagnosed in the seventh decade of life. The illness had a progressive course with escalating seizures in the index case, with fatality at age 63. Diagnosis in adulthood is rare. Epilepsy is more common in the adult than the pediatric SSADH deficiency cohort; neuropsychiatric morbidity remains prominent.

Adolescent presentations of inborn errors of metabolism

Several studies have shown that a large percentage of inborn errors of metabolism is present in adolescent patients. Individually, each diagnosis in this category of diseases is rare; therefore, there is often a significant delay in determining the etiology of a patient's complaints. These disorders can have a wide variety of multisystemic presentations, several of which overlap with more common disorders of adolescence. This review highlights the red-flag findings on history and physical examination indicating a possible inborn error of metabolism. In addition, a systematic approach for evaluating and categorizing these disorders is introduced and demonstrated through case examples. Primary care physicians play a crucial role in the early detection and prompt treatment of patients with late-onset inborn errors of metabolism.

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.

[Inborn errors of metabolism in adult neurology]

Inborn errors of metabolism (IEM) are caused by mutations in genes coding for enzymes and other proteins involved in cell metabolism. Many IEM can be treated effectively. Although IEM have usually been considered pediatric diseases, they can present at any age, mostly with neurological and psychiatric symptoms, and therefore constitute an integral subspeciality of neurology. However, although they are increasingly being recognized, IEM remain rare, and the care for patients should be optimized in specialized reference centers. Since the number of different diseases is very large, the diagnostic approach needs to be rigorous, starting at the clinics and calling upon the additional help of neuroradiology, biochemistry and molecular biology. In practice, it is important for the neurologist to recognize: (1) when to start suspecting an IEM; and (2) how to correlate a given clinical presentation with one of the five major groups of diseases affecting the nervous system. These five groups may be classified as: (a) energy metabolism disorders such as respiratory chain disorders, pyruvate dehydrogenase deficiency, GLUT1 deficiency, fatty-acid β-oxidation defects, and disorders involving key cofactors such as electron transfer flavoprotein, thiamine, biotin, riboflavin, vitamin E and coenzyme Q10; (b) intoxication syndromes such as porphyrias, urea-cycle defects, homocystinurias, organic acidurias and amino acidopathies; (c) lipid-storage disorders such as lysosomal storage disorders (Krabbe disease, metachromatic leukodystrophy, Niemann - Pick disease type C, Fabry disease and Gaucher's disease), peroxisomal disorders (adrenomyeloneuropathy, Refsum disease, disorders of pristanic acid metabolism, peroxisome biogenesis disorders), Tangier disease and cerebrotendinous xanthomatosis; (d) metal-storage diseases such as iron, copper and manganese metabolic disorders; and (e) neurotransmitter metabolism defects, including defects of serotonin, dopamine and glycine metabolism.

Clinical review of genetic epileptic encephalopathies

Seizures are a frequently encountered finding in patients seen for clinical genetics evaluations. The differential diagnosis for the cause of seizures is quite diverse and complex, and more than half of all epilepsies have been attributed to a genetic cause. Given the complexity of such evaluations, we highlight the more common causes of genetic epileptic encephalopathies and emphasize the usefulness of recent technological advances. The purpose of this review is to serve as a practical guide for clinical geneticists in the evaluation and counseling of patients with genetic epileptic encephalopathies. Common syndromes will be discussed, in addition to specific seizure phenotypes, many of which are refractory to anti-epileptic agents. Divided by etiology, we overview the more common causes of infantile epileptic encephalopathies, channelopathies, syndromic, metabolic, and chromosomal entities. For each condition, we will outline the diagnostic evaluation and discuss effective treatment strategies that should be considered.

MRI of childhood epilepsy due to inborn errors of metabolism

OBJECTIVE

The purpose of this pictorial essay is to classify epilepsy syndromes due to inborn errors of metabolism according to age at onset and type of seizure and to show the MRI features of many of the syndromes.

CONCLUSION

Epilepsy syndromes due to inborn errors of metabolism are rare, but it is important to detect them at an early stage because some are treatable. MRI is an important tool in the assessment of these patients.

Epilepsy and inborn errors of metabolism in children

Epilepsy is a frequent symptom in inborn errors of metabolism, with virtually no specific seizure types or EEG signatures. It is most important to look quickly for those few inborn errors of metabolism in which specific therapies such as supplementation of cofactors or diets can make all the difference. If these investigations remain negative, epilepsy has to be treated with conventional antiepileptic drugs. Still, epilepsy is a potentially treatable symptom of many inborn errors of metabolism, and optimal treatment is of great importance for patients and their families.