A case of Ohtahara syndrome with cytochrome oxidase deficiency

Epilepsias na Infância

As crises epilépticas representam um dos mais freqüentes problemas neurológicos na infância. Entre 0,5% e 1% de crianças e adolescentes apresentam uma crise epiléptica associada com um distúrbio metabólico agudo ou um insulto neurológico, muitos dos quais ocorrem no período neonatal. Elevada incidência de epilepsia ocorre no primeiro ano de vida. A síndrome de West ocorre em cerca de 9% das epilepsias na infância, síndrome de Lennox-Gastaut por volta de 1% a 2%, epilepsia de ausência de 10% a 15%, epilepsias mioclônica juvenil ocorre em cerca de 5% e as epilepsia parciais benignas ocorrem em 10% de todas as epilepsias na infância, mas 20% a 25% das epilepsias são diagnosticadas entre 5 e 15 anos.

X-linked intellectual disability gene CASK regulates postnatal brain growth in a non-cell autonomous manner

The phenotypic spectrum among girls with heterozygous mutations in the X-linked intellectual disability (XLID) gene CASK (calcium/calmodulin-dependent serine protein kinase) includes postnatal microcephaly, ponto-cerebellar hypoplasia, seizures, optic nerve hypoplasia, growth retardation and hypotonia. Although CASK knockout mice were previously reported to exhibit perinatal lethality and a 3-fold increased apoptotic rate in the brain, CASK deletion was not found to affect neuronal physiology and their electrical properties. The pathogenesis of CASK associated disorders and the potential function of CASK therefore remains unknown. Here, using Cre-LoxP mediated gene excision experiments; we demonstrate that deleting CASK specifically from mouse cerebellar neurons does not alter the cerebellar architecture or function. We demonstrate that the neuron-specific deletion of CASK in mice does not cause perinatal lethality but induces severe recurrent epileptic seizures and growth retardation before the onset of adulthood. Furthermore, we demonstrate that although neuron-specific haploinsufficiency of CASK is inconsequential, the CASK mutation associated human phenotypes are replicated with high fidelity in CASK heterozygous knockout female mice (CASK^(+/-)). These data suggest that CASK-related phenotypes are not purely neuronal in origin. Surprisingly, the observed microcephaly in CASK^(+/-) animals is not associated with a specific loss of CASK null brain cells indicating that CASK regulates postnatal brain growth in a non-cell autonomous manner. Using biochemical assay, we also demonstrate that CASK can interact with metabolic proteins. CASK knockdown in human cell lines cause reduced cellular respiration and CASK^(+/-) mice display abnormalities in muscle and brain oxidative metabolism, suggesting a novel function of CASK in metabolism. Our data implies that some phenotypic components of CASK heterozygous deletion mutation associated disorders represent systemic manifestation of metabolic stress and therefore amenable to therapeutic intervention.

Epilepsy surgery for early infantile epileptic encephalopathy (ohtahara syndrome)

Early infantile epileptic encephalopathy or Ohtahara syndrome is the earliest form of the age-dependent epileptic encephalopathies. Its manifestations include tonic spasms, focal motor seizures, suppression burst pattern, pharmaco-resistance, and dismal prognosis. The purpose of this study was to evaluate the effectiveness of epilepsy surgery in selected infants. We identified 11 patients, 9 from the literature and 2 from our institution that fulfilled diagnostic criteria of Ohtahara syndrome and had undergone epilepsy surgery in infancy. Seven of the 11 infants have remained seizure free (Engel class IA) and four are reportedly having rare to infrequent seizures (Engel class IIB). All patients experienced "catch up" development. In contrast to Ohtahara's15 pharmacotherapy managed patients, who had a mortality rate of approximately fifty percent, and those that survived continued to have seizures and were severely impaired, the outcome of selected surgically managed patients is much more favorable.

Early-onset epileptic encephalopathies: Ohtahara syndrome and early myoclonic encephalopathy

Ohtahara syndrome and early myoclonic encephalopathy are the earliest presenting of the epileptic encephalopathies. They are typically distinguished from each other according to specific clinical and etiologic criteria. Nonetheless, considerable overlap exists between the two syndromes in terms of clinical presentation, prognosis, and electroencephalographic signature. Newer understandings of underlying etiologies of these conditions may support the previously suggested concept that they represent a single spectrum of disease rather than two distinct disorders. We review both syndromes, with particular focus on the underlying genetics and pathophysiology and implications regarding the classification of these conditions.

Epileptic encephalopathies in adults and childhood

Epileptic encephalopathies are motor-mental retardations or cognitive disorders secondary to epileptic seizures or epileptiform activities. Encephalopaties due to brain damage, medications, or systemic diseases are generally not in the scope of this definition, but they may rarely accompany the condition. Appropriate differential diagnosis of epileptic seizures as well as subclinical electroencephalographic discharges are crucial for management of seizures and epileptiform discharges and relative regression of cognitive deterioration in long-term followup. Proper antiepileptic drug, hormonal treatment, or i.v. immunoglobulin choice play major role in prognosis. In this paper, we evaluated the current treatment approaches by reviewing clinical electrophysiological characteristics of epileptic encephalopathies.

Ohtahara syndrome with emphasis on recent genetic discovery

Ohtahara syndrome or Early Infantile Epileptic Encephalopathy (EIEE) with Suppression-Burst, is the most severe and the earliest developing age-related epileptic encephalopathy. Clinically, the syndrome is characterized by early onset tonic spasms associated with a severe and continuous pattern of burst activity. It is a debilitating and early progressive neurological disorder, resulting in intractable seizures and severe mental retardation. Specific mutations in at least four genes (whose protein products are essential in lower brain's neuronal and interneuronal functions, including mitochondrial respiratory chains have been identified in unrelated individuals with EIEE and include: (a) the ARX (aristaless-related) homeobox gene at Xp22.13 (EIEE-1 variant); (b) the CDKL5 (SYK9) gene at Xp22 (EIEE-2 variant); (c) the SLC25A22 (GC1) gene at 11p15.5 (EIEE-3 variant); and (d) the Stxbp1 (MUNC18-1) gene at 9q34-1 (EIEE-4 variant). A yet unresolved issue involves the relationship between early myoclonic encephalopathy (EME-ErbB4 mutations) versus the EIEE spectrum of disorders.

A neurophysiological-metabolic model for burst suppression

Burst suppression is an electroencepholagram (EEG) pattern in which high-voltage activity alternates with isoelectric quiescence. It is characteristic of an inactivated brain and is commonly observed at deep levels of general anesthesia, hypothermia, and in pathological conditions such as coma and early infantile encephalopathy. We propose a unifying mechanism for burst suppression that accounts for all of these conditions. By constructing a biophysical computational model, we show how the prevailing features of burst suppression may arise through the interaction between neuronal dynamics and brain metabolism. In each condition, the model suggests that a decrease in cerebral metabolic rate, coupled with the stabilizing properties of ATP-gated potassium channels, leads to the characteristic epochs of suppression. Consequently, the model makes a number of specific predictions of experimental and clinical relevance.

Mitochondria and neonatal epileptic encephalopathies with suppression burst

The mitochondrion is a key cellular structure involved in many metabolic functions such as ATP synthesis by oxidative phosphorylation, tricarboxylic acid cycle or fatty acid oxidation. These pathways are fundamental for biological processes such as cell proliferation or death. In the central nervous system, mitochondria dysfunctions have been involved in many neurological diseases and age-related neurodegenerative disorders, including epilepsy, Alzheimer's and Parkinson's diseases. Mitochondrial diseases are frequently caused by a disruption of the respiratory chain. Nevertheless, other mitochondrial functions, including organellar dynamics or metabolite transport, could also be involved in such pathologies. Here we described mitochondrial dysfunctions in a very severe, intractable and relatively rare neonatal epileptic encephalopathy, the Ohtahara syndrome. This condition is characterized by neonatal onset of seizures, interictal electroencephalogram with suppression burst pattern and a very poor outcome with very severe psychomotor retardation or death. The etiology of this disease remains elusive but seems to be very heterogeneous including brain malformations, metabolic errors, transcription factor and synaptic vesicle release defects. In this review, we discuss first the Ohtahara syndrome caused by mitochondrial respiratory chain damages, suggesting that these defects could be more common than previously thought. Then, we will adress the importance of the mitochondrial glutamate carrier SLC25A22 in these pathologies, since mutations of this gene were described in two distinct families. These findings suggest that glutamate metabolism should also be considered as an important cause of the Ohtahara syndrome.

Ohtahara syndrome with biotinidase deficiency

Ohtahara syndrome is a rare epileptic encephalopathy in infants; the underlying etiology is generally thought to be structural brain malformations. The authors present a rare case of this type of epileptic encephalopathy in which a treatable metabolic condition such as biotinidase deficiency was suspected and diagnosed, and early institution of appropriate therapy led to a good clinical outcome.

"Epileptic encephalopathy" of infancy and childhood: electro-clinical pictures and recent understandings

There is growing interest in the diagnosis of cognitive impairment among children with epilepsy. It is well known that status of seizures control has to be carefully investigated because it can be sufficient "per se" to cause progressive mental deterioration conditions. Subclinical electroencephalographic discharges may have subtle effects on cognition, learning and sleep patterns, even in the absence of clinical or sub-clinical seizures. In this respect, electroencephalographic monitoring (long-term and nocturnal recording) and in particular an all night video-polysomnography (V-NPSG) record can be crucial to detect the presence of unrecognized seizures and/or an inter-ictal nocturnal EEG discharge increasing. Epileptic encephalopathies (EE) are a group of conditions in which the higher cognitive functions are deteriorate as a consequence of epileptic activity, which, in fact, consists of frequent seizures and/or florid and prolonged interictal paroxysmal discharges, focal or generalized. AEDs represent the first line in opposing the burden of both, the poor seizures control and the poor interictal discharges control, in the cognitive deterioration of EE affected children. Thus, to improve the long-term cognitive/behavioural prognosis in these refractory epileptic children, it should be taken into account both a good seizures control and a strict sleep control, choosing carefully antiepileptic drugs which are able to control not only seizures clinically recognizable but even the EEG discharges onset and its increasing and spreading during sleep. Here, we review the efficacy and safety of the newer AEDs that, to date, are used in the treatment of EE in infancy and childhood.

Neonatal Seizures: When to Consider and How to Investigate for an Inborn Error of Metabolism

Seizures occur more frequently in the neonatal period than in the remainder of childhood. Neonatal seizures can have different aetiologies. Inborn errors of metabolism are rare causes of seizures in the newborn. However, they are an important cause of intractable neonatal seizures, accounting for 30% of cases. Diagnosis is necessary for timely institution of appropriate treatment and is important in determining clinical outcome. As these are genetic conditions, it allows for appropriate genetic counselling. We describe the clinical presentation of neonatal seizures and the investigation findings in symptomatic neonatal seizures and epilepsy syndromes that arise in the neonatal period. The approach in diagnosis and investigation of an underlying inborn error of metabolism is described and inborn errors of metabolism that are important causes of neonatal seizures are reviewed.

A case of Ohtahara syndrome with mitochondrial respiratory chain complex I deficiency

Ohtahara syndrome (OS) is known as an intractable epileptic syndrome in neonatal and early infantile period, differentiated from early myoclonic encephalopathy (EME) in its etiology. We report a patient with OS associated with mitochondrial respiratory chain complex (MRC) I defect. With ketogenic diet and mitochondrial cocktail therapy, seizures were completely controlled and suppression-burst patterns disappeared 3 months after starting treatment. It is suggested that OS could be caused by specific metabolic disorder such as MRC defect and the intensive therapies including ketogenic diet, vitamin and coenzyme therapy and antioxidant treatment might be helpful for some patients.

Respiratory chain complex I deficiency in an infant with Ohtahara syndrome

We report an infant with complex I deficiency of the mitochondrial respiratory chain whose most conspicuous symptom at presentation was an Ohtahara syndrome. Review of the literature suggest that association of these two conditions is extremely rare. Despite the few cases reported, in our view Ohtahara syndrome should be considered as one of the forms of presentation of mitochondrial dysfunction.

Ohtahara syndrome: With special reference to its developmental aspects for differentiating from early myoclonic encephalopathy

Ohtahara syndrome (OS) is well known as a peculiar early onset epileptic syndrome with serious prognosis. The outline of OS, mainly in relation to the evolution with age, and differentiation from related conditions, particularly early myoclonic encephalopathy (EME) were mentioned.

RESULTS

Etiologically, structural brain lesions are most probable in OS, and non-structural/metabolic disorders in EME. Clinically, tonic spasms are the main seizures in OS, while myoclonia and frequent partial motor seizures in EME. Another difference is noted in EEG findings: suppression-bursts (SB) are consistently observed in both waking and sleeping states in OS, but suppression-bursts become more apparent in sleep in EME. The course observation clarifies differences between both syndromes; SBs evolve to hypsarrhythmia around 3-4 months of age, and sometimes further to diffuse slow spike-waves in OS. In contrast, in EME suppression-bursts may persist up to late childhood after a transient evolution to hypsarryhtmia in the middle to late infancy. Transition between syndromes is also specific; OS evolves to West syndrome, and further to Lennox-Gastaut syndrome with age, but EME persists long without such evolution excepting a transient phase of West syndrome.

CONCLUSION

These clinicoelectrical characteristics and differential points strongly indicate the efficiency of the developmental study to delineate both syndromes.

Are early myoclonic encephalopathy (EME) and the Ohtahara syndrome (EIEE) independent of each other?

BACKGROUND

Early myoclonic encephalopathy (EME) and the Ohtahara syndrome are currently listed as two separate syndromes in the classification of epilepsies. The most prominent differentiating points are the observations that patients with Ohtahara syndrome experience predominantly tonic seizures; their seizures evolve to infantile spasms and the prognosis is often worse than patients with EME.

SUMMARY POINTS

We performed a literature review of published cases. Although syndromes may have distinct courses, the differentiation early on may be impossible as both myoclonus and tonic seizures may coexist. There is also an overlap in the etiologies. Tonic seizures are considered a manifestation of brainstem dysfunction and it is possible that this is more prominent in Ohtahara syndrome. To date, there are 17 autopsy cases (12 presumed to be Ohtahara cases and 5 EME). Evidence of hindbrain pathology was present in all. Tonic seizures or tonic posturing was a feature of all cases. We suggest that the two syndromes may represent a continuum and that the prominence of tonic seizures in the Ohtahara syndrome may be an indication of brainstem dysfunction which may play an important role in the subsequent transition to infantile spasms.

Epilepsy syndromes in infancy

An increasing number of infantile epilepsy syndromes have been recognized. However, a significant number of infants (children aged 1-24 months) do not fit in any of the currently used subcategories. This article reviews the clinical presentation, electroencephalographic findings, evolution, and management of the following entities: early infantile epileptic encephalopathy, early myoclonic epilepsy, infantile spasms/West syndrome, severe myoclonic epilepsy of infancy, myoclonic-astatic epilepsy, generalized epilepsy with febrile seizures plus, malignant migrating partial seizures of infancy, hemiconvulsions-hemiplegia-epilepsy, benign myoclonic epilepsy, and benign familial/nonfamilial infantile seizures. Issues related to their classification are addressed.

Epileptic Encephalopathies in Early Infancy With Suppression-Burst

Early infantile epileptic encephalopathy with suppression-burst, or Ohtahara syndrome (OS), and early myoclonic encephalopathy (EME) are epileptic encephalopathies with onset of frequent seizures in the neonatal and early infancy period and with a characteristic EEG pattern, namely, suppression-burst, in which higher-voltage bursts of slow waves mixed with multifocal spikes alternate with isoelectric suppression phase. Their nosologic independence is now widely accepted, although some controversy initially occurred because of their common characteristics such as age of onset, EEG features, seizure intractability, and poor prognosis. Major differences between the two syndromes include (1) tonic spasms in OS versus partial seizures and erratic myoclonias in EME, (2) continuous suppression-burst pattern in both waking and sleeping states in OS versus this EEG pattern almost limited to sleep in EME, and (3) static structural brain damage in OS versus genetic or metabolic disorders in EME. The most important differentiating point is their evolutional pattern with age, which may reflect their pathophysiologic difference. Ohtahara syndrome evolves to West syndrome and further to Lennox-Gastaut syndrome with age, but EME demonstrates no unique evolution; namely, it continues as such for a long time or changes into partial epilepsy or severe epilepsy with multiple independent spike foci.

Neonatal seizures and syndromes

Neonatal seizures frequently accompany neonatal encephalopathies. Seizures occur in approximately 1.8-5/1,000 live births in this country and are caused by virtually any condition that affects neonatal brain function. This review provides a simple classification of seizures and emphasizes that many abnormal intermittent behaviors in this age group are not accompanied by ictal EEG patterns. Additionally, < or =50% of neonatal seizures are not associated with abnormal clinical behavior. This is a common phenomenon, particularly after anticonvulsant treatment in which the clinical seizures are suppressed but electrographic seizures continue unabated. Seizures also may be caused by genetic disorders, several of which are benign, familial, and caused by channelopathies involving potassium channels. The review also discusses the epileptic syndromes seen in neonates, including early myoclonic encephalopathy, Ohtahara syndrome, pyridoxine dependency, and glucose transporter type 1 syndrome.

Early-infantile epileptic encephalopathy with suppression-bursts, Ohtahara syndrome; its overview referring to our 16 cases

Ohtahara syndrome (OS) is characterized by frequent tonic spasms, with or without clustering, of early onset within a few months of life, and a suppression-burst (S-B) pattern in electroencephalography (EEG). Tonic spasms occur in not only waking but also sleeping state in most cases. Partial seizures are observed in about one-third of cases. Brain imagings reveal structural abnormalities including malformations, notably asymmetric lesions in most cases.S-B pattern is persistently observed regardless of circadian cycle. Bursts of 1-3s duration alternate with nearly flat suppression phase of 2-5s at an approximately regular rate; 5-10s of burst-burst interval. Some asymmetry in S-B is noted in about two-thirds of cases. Ictal EEG of tonic spasms shows principally desynchronization with or without initial rapid activity. Tonic spasms appear concomitant with bursts. Characteristic age-dependent evolution from OS to West syndrome (WS) in many cases, and further from WS to Lennox-Gastaut syndrome (LGS) in some, proceed concomitantly with EEG transition from S-B to hypsarrhythmia at around age 3-6 months, and further from hypsarrhythmia to diffuse slow spike-waves at around age 1. Under the inclusive concept of the age-dependent epileptic encephalopathy, OS, WS, and LGS have common characteristics such as age preference, frequent minor generalized seizures, and continuous massive epileptic EEG abnormality. Mutual transition suggests the same pathophysiology among three syndromes and the age factor should be considered as the common denominator responsible for the manifestation of each of their own specific clinico-electrical features. Namely, these syndromes may be the age-specific epileptic reaction to various non-specific exogenous brain insults, acting at the specific developmental stages.

Catastrophic epilepsy in childhood

Although for most children epilepsy is a relatively benign disorder, for some, epilepsy can be designated as "catastrophic" because the seizures are so difficult to control and because they are strongly associated with mental retardation. The catastrophic childhood epilepsies include uncommon disorders such as early infantile epileptic encephalopathy with suppression burst, severe myoclonic epilepsy of infancy, and epilepsy with myoclonic-astatic seizures. There are other syndromes that are relatively common such as infantile spasms, Lennox-Gastaut syndrome, and Sturge-Weber syndrome. Many children with catastrophic epilepsy have the seizures as a result of underlying brain abnormalities that will inevitably lead to mental retardation whether or not they have seizures. In some patients, however, the mental retardation appears to be caused by the seizures. Developmental plasticity provides children with an opportunity to recover from significant brain injuries. However, the plasticity may also be the cause of the mental retardation. In such patients, control of the seizures may lead to more normal intellectual development. Thus, every effort should be made to control seizures in children with catastrophic epilepsy.