Electroclinical characteristics of hemimegalencephaly

The relationship between the characteristics of burst suppression pattern and different etiologies in epilepsy

To analyze the relationship between the characteristics of burst suppression (BS) pattern and different etiologies in epilepsy. Patients with a BS pattern who were younger than 6 months old were screened from our electroencephalogram (EEG) database. The synchronized and symmetric BS patterns under different etiologies in epilepsy were analyzed. A total of 32 patients had a BS pattern on EEG. The etiologies included genetic disorders (37.5%), cortical malformations (28.1%), inborn errors of metabolism (12.5%), and unknown (21.9%). Twenty-five patients were diagnosed with Ohtahara syndrome, one as early myoclonic encephalopathy, and one as epilepsy of infancy with migrating focal seizure. Five cases could not be classified into any epileptic syndrome. Asynchronous BS pattern was identified in 18 cases, of which 13 (72%) patients had genetic and/or metabolic etiologies. Synchronous BS pattern was identified in 14 cases, of which 8 (57%) patients had structural etiologies. Twenty-three patients had symmetric BS patterns, of which 15 (65%) patients had genetic etiologies. Nine patients had asymmetric BS patterns, of which 8 (89%) patients had structural etiologies. Patients with genetic epilepsies tended to have asynchronous and symmetric BS patterns, whereas those with structural epilepsies were more likely to have synchronous and asymmetric BS patterns.

Evolution of epilepsy in hemimegalencephaly from infancy to adulthood: Case report and review of the literature

Hemimegalencephaly (HME) is a rare disorder of cortical development with overgrowth of one cerebral hemisphere. Patients have intellectual delay, hemiparesis and severe epilepsy. Drug-resistant epilepsy is often treated with a hemispherectomy. We review the literature on HME natural history and report a 26-year-old man with HME who did not undergo hemispherectomy in childhood with recurrent focal convulsive or non-convulsive status epilepticus.

Few patients with HME have been followed into adulthood. Reported adult cases have milder epilepsy or underwent hemispherectomy in childhood. Patients surviving to adulthood have poor outcomes, regardless of treatment method, although seizure burden is improved with hemispherectomy.

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Hemimegalencephaly is a rare disorder of neuronal migration characterized by epilepsy, developmental delay and hemiparesis.

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Outcomes of hemimegalencephaly are generally poor; however, this is typically reported in pediatric populations, not adults.

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Hemispherectomy is beneficial in reducing seizure burden; however, most do not obtain seizure-freedom.

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Seizures are typically focal onset; however, the epileptogenic area may increase with poor seizure control.

Two siblings with cortical dysplasia: Clinico-electroencephalographic features

The older of two siblings began to have spasms and partial seizures at 1 month of age. Head magnetic resonance imaging showed an abnormal area in the left temporo-parieto-occipital region. Interictal electroencephalogram (EEG) showed a suppression-burst pattern. Adrenocorticotropic hormone stopped the spasms, but the seizures continued. Clonazepam, carbamazepine, zonisamide, and clobazam were ineffective. She underwent focal resection at age 8 months. Postoperatively, the seizures disappeared. Histopathologically, the lesion appeared to be focal cortical dysplasia type IIa. The younger sibling had spasms from birth. Head magnetic resonance imaging showed left hemi-megalencephaly. Interictal EEG showed a suppression-burst pattern. Phenobarbital, valproic acid, and zonisamide were ineffective. He underwent hemispherotomy at age 2 months and became seizure free. The histopathological features were consistent with those of hemi-megalencephaly. The siblings' EEG and clinical courses had some similarities. These siblings' conditions may have the same genetic background.

Early modified functional hemispherectomy in a young infant with Ohtahara syndrome and hemimegalencephaly

We report on the youngest infant treated with modified functional hemispherectomy at the age of 5 months for Ohtahara syndrome and hemimegalencephaly as underlying pathology, and we depict the favorable outcome regarding seizure control and psychomotor development. These results highlight the potential usefulness of early surgery in such conditions.

Hemispheric malformations of cortical development: surgical indications and approach

INTRODUCTION

The term "hemispheric malformation of cortical development" (MCD) has come into the medical lexicon in the past 20 years as improvements and availability of advanced imaging techniques have permitted more precise diagnosis of a variety of brain developmental disorders that affect large regions of brain. These conditions are united by their propensity to elicit seizures that are difficult to control with medication in the children who suffer them.

PURPOSE

The goal of surgical intervention is always to achieve seizure freedom and thereby give the affected child the best possible hope for neurological development. Even when seizure freedom cannot be achieved, a reduction in seizure burden is necessary to permit the survival of the child in many cases of MCD.

EVALUATION

A presurgical evaluation of a patient presenting with severe epilepsy and a possible hemispheric malformation can be divided into three stages. The first includes an evaluation of available imaging, clinical, and genetic data to accurately diagnose the child and help determine if surgical intervention is an option. The next includes an evaluation of EEG and neurological data, although this has limited utility in many clinical circumstances. Finally, a clinical team must decide upon an appropriate surgical strategy among a variety of options.

CONCLUSIONS

In this review, we will examine the set of diagnoses and associated imaging characteristics that describe the set of conditions for which surgical intervention is a possibility. We include a discussion of available surgical options, describing our own experience with surgery for MCD and the associated postoperative considerations including rates of seizure freedom, considerations for reoperation, and hydrocephalus.

Unihemispheric burst suppression

Burst suppression (BS) consists of bursts of high-voltage slow and sharp wave activity alternating with periods of background suppression in the electroencephalogram (EEG). When induced by deep anesthesia or encephalopathy, BS is bihemispheric and is often viewed as a non-epileptic phenomenon. In contrast, unihemispheric BS is rare and its clinical significance is poorly understood. We describe here two cases of unihemispheric BS. The first patient is a 56-year-old woman with a left temporoparietal tumor who presented in convulsive status epilepticus. EEG showed left hemispheric BS after clinical seizure termination with lorazepam and propofol. The second patient is a 39-year-old woman with multiple medical problems and a vague history of seizures. After abdominal surgery, she experienced a convulsive seizure prompting treatment with propofol. Her EEG also showed left hemispheric BS. In both cases, increasing the propofol infusion rate resulted in disappearance of unihemispheric BS and clinical improvement. The prevailing view that typical bihemispheric BS is non-epileptic should not be extrapolated automatically to unihemispheric BS. The fact that unihemispheric BS was associated with clinical seizure and resolved with propofol suggests that, in both cases, an epileptic mechanism was responsible for unihemispheric BS.

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.

Epidermal nevus syndrome

Epidermal nevus syndrome (ENS) is an inclusive term for a heterogeneous group of congenital disorders characterized by the presence of epidermal nevi associated with systemic involvement. These disorders, as are all primary neurocutaneous syndromes, are neurocristopathies. The epidermal nevi that follow the lines of Blaschko and most systemic anomalies in skeletal, ocular, cardiovascular, endocrine, and orodental tissues, as well as lipomas, are due to defective neural crest. The most important and frequent anomaly in the brain in all forms of epidermal nevus syndromes (ENSs) is hemimegalencephaly (HME). This malformation often is not recognized, despite being the principal cause of neurological manifestations in ENSs. They consist mainly of epilepsy and developmental delay or intellectual disability. The onset of epilepsy in ENS usually is in early infancy, often as infantile spasms. Several syndromic forms have been delineated. I propose the term "Heide's syndrome" for those distinctive cases with the typical triad of hemifacial epidermal nevus, ipsilateral facial lipoma, and hemimegalencephaly. Most ENSs are sporadic. The mechanism is thought to be genetic mosaicism with a lethal autosomal dominant gene. Specific genetic mutations (PTEN, FGFR3, PIK3CA, and AKT1) have been documented in some patients. The large number of contributors for over more than a century and a half to the description of these disorders precludes the use of new author eponyms.

Hemimegalencephaly in an adult with normal intellectual function and mild epilepsy

Hemimegalencephaly is a rare congenital brain malformation, usually associated with mental retardation, * refractory epilepsy, and progressive neurological deficits. We report the case of a 19-year-old female with de novo diagnosis of right hemimegalencephaly, normal intellectual function, and history of non-refractory epilepsy. She presented with weakness and paraesthesia of the left leg. Extensive evaluation was negative for other causes for the weakness, which was attributed to progressive neurological damage secondary to long-standing subclinical epileptic activity in the hemimegalencephalic hemisphere. This patient underwent a cerebral fluorodeoxyglucose positron emission tomography that demonstrated near-normal cortical metabolism. Formal neuropsychological evaluation revealed mild deficits in the affected hemisphere, but preserved general intellectual function. This case illustrates the wide phenotypic variations in this condition and raises questions about prenatal counselling for hemimegalencephaly.

[Ohtahara syndrome--early infantile epileptic encephalopathy]

DEFINITION

Ohtahara syndrome (early infantile epileptic encephalopathy with suppression bursts), is the earliest developing form of epileptic encephalopathy. ETHIOLOGY: It considered to be a result of static structural developing brain damage.

CLINICAL PICTURE

Variable seizures develop mostly within the first 10 days of life, but may occur during the first hour after delivery. The most frequently observed seizure type are epileptic spasms, which may be either generalized and symmetrical or lateralized .The tonic spasms may occur in clusters or singly, while awake and during sleep alike. The duration of spasms is up to 10 seconds, and the interval between spasms within cluster ranges from 9 to 15 seconds. In one third of cases, other seizure types include partial motor seizures or hemiconvulsions The disorder takes a progressively deteriorating course with increasing frequency of seizures and severe retardation of psychomotor development.

DIAGNOSTIC WORKUP

In the initial stage of Ohtahara syndrome, interictal EEG shows a pattern of suppression-burst with high-voltage paroxysmal discharges separated by prolonged periods of nearly flat tracing that last for up to 18 seconds.

PROGNOSIS AND TREATMENT

Half of the reported children having Ohtahara syndrome die in infancy. Anticonvulsant helps little in controlling the seizures and halting the deterioration of psychomotor development. Severe psychomotor retardation is the rule. With time, the disorder may evolve into West syndrome or partial epilepsy. Psychomotor development may be slightly better if the infants do not develop West and later Lennox-Gastaut syndrome.

Approach to pediatric epilepsy surgery: State of the art, Part II: Approach to specific epilepsy syndromes and etiologies

The second of this 2-part review depicts the specific approach to the common causes of pediatric refractory epilepsy amenable to surgery. These include tumors, malformations due to abnormal cortical development, vascular abnormalities and certain epileptic syndromes. Seizure freedom rates are high (usually 60-80%) following tailored focal resection, lesionectomy, and hemispherectomy. However, in patients in whom the epileptogenic zone overlaps with unresectable eloquent cortex, and in certain epileptic syndromes, seizure freedom may not be achievable. In such cases, palliative procedures such as callosotomy, multiple subpial transections and vagus nerve stimulation can achieve reduction in seizure severity but rarely seizure freedom. Integration of the new imaging techniques and the concepts of neuronal plasticity, the epileptogenic lesion, the ictal onset, symptomatogenic, irritative, and epileptogenic zones is an expanding and dynamic process that will allow us, in the future, to better decide on the surgical approach of choice and its timing.

Malformations of cortical development and epilepsy

Malformations of cortical development (MCDs) are macroscopic or microscopic abnormalities of the cerebral cortex that arise as a consequence of an interruption to the normal steps of formation of the cortical plate. The human cortex develops its basic structure during the first two trimesters of pregnancy as a series of overlapping steps, beginning with proliferation and differentiation of neurons, which then migrate before finally organizing themselves in the developing cortex. Abnormalities at any of these stages, be they environmental or genetic in origin, may cause disruption of neuronal circuitry and predispose to a variety of clinical consequences, the most common of which is epileptic seizures, A large number of MCDs have now been described, each with characteristic pathological, clinical, and imaging features. The causes of many of these MCDs have been determined through the study of affected individuals, with many MCDs now established as being secondary to mutations in cortical development genes. This review will highlight the best-known of the human cortical malformations associated with epilepsy. The pathological, clinical, imaging, and etioiogic features of each MCD will be summarized, with representative magnetic resonance imaging (MRI) images shown for each MCD, The malformations tuberous sclerosis, focal cortical dysplasia, hemimegalencephaiy, classical iissencephaly, subcortical band heterotopia, periventricular nodular heterotopia, polymicrogyria, and schizencephaly will be presented.

Outcome of hemispheric surgeries for refractory epilepsy in pediatric patients

BACKGROUND

Hemispheric brain lesions are commonly associated with early onset of catastrophic epilepsies and multiple seizure types. Hemispheric surgery is indicated for patients with unilateral intractable epilepsy. Although described more than 50 years ago, several new techniques for hemispherectomy have only recently been proposed aiming to reduce operatory risks and morbidity.

MATERIALS AND METHODS

We present the clinical characteristics, presurgical workup, and postoperative outcome of a series of pediatric patients who underwent hemispherectomy for medically intractable epileptic seizures. Thirty-nine patients with medically intractable epilepsy underwent surgery from 1996 to 2005.

RESULTS AND DISCUSSION

We analyzed demographic data, interictal and ictal EEG findings, age at surgery, surgical technique and complications, and postsurgical seizure outcome. There were 74.4% males. Tonic and focal motor seizures occurred in 30.8 and 20.5% of the patients. Most frequent etiologies were Rasmussen encephalitis (30.8%) and malformation of cortical development (23.1%). Postsurgical outcomes were Engel classes I and II for 61.5% of the patients. In general, 89.5% of the patients exhibited at least a 90% reduction in seizure frequency. All patients had acute worsening of hemiparesis after surgery. Basically, two surgical techniques have been employed, both with similar results, although a trend has been noted toward one of the procedures which produced consistently complete disconnection. Patients with hemispheric brain lesions usually have abnormal neurological development and intractable epilepsy. When video-EEG monitoring and magnetic resonance imaging show unilateral disease, the patient may evolve with a good surgical outcome. We showed that a marked reduction in seizure frequency may be achieved, with acceptable neurological impairments.

Hemimegalencephaly: clinical implications and surgical treatment

INTRODUCTION

Hemimegalencephaly (HME) is a quite rare malformation of the cortical development arising from an abnormal proliferation of anomalous neuronal and glial cells that generally leads to the hypertrophy of the whole affected cerebral hemisphere. The pathogenesis of such a complex malformation is still unknown even though several hypotheses are reported in literature.

BACKGROUND

HME can occur alone or associated with neurocutaneous disorders, such as neurofibromatosis, epidermal nevus syndrome, Ito's hypomelanosis, and Klippel-Trenonay-Weber syndrome. The clinical picture is usually dominated by a severe and drug-resistant epilepsy. Other common findings are represented by macrocrania, mean/severe mental retardation, unilateral motor deficit, and hemianopia. The EEG shows different abnormal patterns, mainly characterized by suppression burst and/or hemihypsarrhythmia. Although neuroimaging and histologic investigations often show typical findings (enlarged hemisphere, malformed ventricular system, alteration of the normal gyration), the differential diagnosis with other disorders of the neuronal and glial proliferation may be difficult to obtain. Hemispherectomy/hemispherotomy is the most effective treatment to control seizure, and it also seems to provide good results on the psychomotor development when performed early, as demonstrated by the literature review and by the reported personal series reported here (20 children). The surgical therapy of HME, however, is still burdened by a quite high complication rate and mortality risk.

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.

Clinical aspects of hemimegalencephaly by means of a nationwide survey

We surveyed Japanese patients with hemimegalencephaly by means of a questionnaire. Clinical findings, including intellectual and motor function levels and epileptic symptoms, were investigated. All 44 patients (28 males and 16 females) with hemimegalencephaly were sporadic. Sixteen patients had underlying neurocutaneous syndromes. The number of patients with right-sided hemimegalencephaly (n = 29) was almost twice that of patients with left-sided hemimegalencephaly (n = 15). Forty-one patients had mental retardation and hemiparesis and 14 patients were bedridden. All patients had epileptic seizures, which first appeared within a month in 18 cases and within 6 months in 11 cases. In 42 patients, magnetic resonance imaging revealed both cortical and white-matter abnormalities in the affected hemisphere. Antiepileptic drugs were not very effective. Fifteen patients were surgically treated. Eleven patients underwent functional hemispherectomy, which resulted in fairly good seizure control and improved development. There is a correlation between the onset of epilepsy and the degree of clinical severity of motor deficit and intellectual level. Neither underlying disorders nor laterality of the affected side was related to the degree of clinical severity.

The Nonmalformed Hemisphere Is Secondarily Impaired in Young Children with Hemimegalencephaly: A Pre- and Postsurgery Study with SPECT and EEG

PURPOSE

To study separately the functional value of each cerebral hemisphere in hemimegalencephaly (HME). HME is a unique model of unilateral hemispheric lesion, but one suspects that the non-HME hemisphere also could be functionally impaired because the postsurgery outcome is less favorable than expected.

METHODS

We performed simultaneous prolonged EEG and 133-xenon SPECT (single-photon emission computed tomography); we measured the absolute values of cerebral blood flow (CBF) in both hemispheres and compared them with the normal values previously acquired. Thirteen patients (aged 5-38 months) underwent 31 examinations, 20 before surgery (hemispherotomy) and 11 after.

RESULTS

In the HME hemisphere, we confirmed the presurgical mixture of increased and decreased CBF due to intermittent ictal discharges. After surgery, CBF was decreased in most cases. In the non-HME hemisphere, presurgery CBF was abnormal in 60% of the patients, increased and related mostly to diffuse interictal spikes on the same side, whereas normal CBF cases had focal spikes. After surgery, CBF was normal in 82% of cases, corresponding to an EEG without diffuse spikes. In the six patients longitudinally studied, CBF dramatically decreased after surgery in the HME hemisphere, whereas in the non-HME hemisphere, CBF was mostly normal very early (three fourths before 2 months), increased as soon as 3 months, and normalized only after hemispherotomy, the more rapidly the child was operated on, the earlier it was.

CONCLUSIONS

This study shows that the function of the nonmalformed hemisphere is impaired as soon as the first months of the course of HME but can be restored after surgery. Our data support the recommendations to operate on the children as early as possible.

Bilateral decreased oxygenation during focal status epilepticus in a neonate with hemimegalencephaly

Early surgical removal of a dysplastic hemisphere appears to be beneficial for neonates with hemimegalencephaly and medically resistant seizures. We analyzed the changes in the cerebral regional oxygen saturation index in a neonate with tuberous sclerosis and right hemimegalencephaly (1) during seven episodes of right hemisphere electroencephalographic status epilepticus with and without clinical manifestations and (2) after right hemispherectomy. The cerebral regional oxygen saturation index demonstrated marked fluctuations and progressive decline in both hemispheres during the episodes and normal values in the remaining hemisphere after surgery. We speculate that decreased oxygenation of the nonepileptic cerebral hemisphere in patients with hemimegalencephaly and medically resistant seizures can contribute to the production of global neurologic impairments in these patients and that the benefits of early hemispherectomy are due to the improved oxygenation of the nondysplastic hemisphere following surgery.

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.

Hemimegalencephaly: part 1. Genetic, clinical, and imaging aspects

Hemimegalencephaly is a rare hamartomatous malformation of the brain, remarkable for its extreme asymmetry. It can be isolated or associated with several neurocutaneous syndromes; less frequently, it also involves the brain stem and cerebellum. Traditionally, hemimegalencephaly has been considered a primary neuroblast migratory disturbance. At present, genetic theories of pathogenesis and modern histopathology provide a basis for this complex malformation as a primary disturbance in cellular lineage, differentiation, and proliferation, interacting with a disturbance in gene expression of body symmetry, with earlier onset than radial neuroblast migration. From my personal experience with 10 patients with hemimegalencephaly and review of the literature, I have found the same clinical neurologic, neuroimaging, and neuropathologic features in isolated and syndromic hemimegalencephaly. Magnetic resonance imaging (MRI) reveals abnormal gyration, ventriculomegaly, colpocephaly, an "occipital sign" (displacement of the occipital lobe across the midline), and increased volume and T2 signal of white matter, in addition to the overall increased size of the involved hemisphere. Mild, moderate, and severe grades of severity can be recognized, providing a functional neurologic prognosis and therapeutic plan. Early diagnosis is crucial because despite neuroimaging and pathologic evidence, hemimegalencephaly sometimes still is unrecognized. Also, misdiagnosis of obstructive hydrocephalus or cerebral neoplasm can lead to unnecessary surgical procedures. Although hemispherectomy has a high morbidity, it is recommended early for patients with severe, intractable epilepsy. The mildest forms of hemimegalencephaly are infrequent and the least recognized.

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.

Spasms in clusters in epilepsies other than typical West syndrome

Although spasms in clusters are one of the major characteristics of West syndrome (WS), there are a significant number of patients who show spasms in clusters but do not fit the standard pattern of WS. It is possible to divide these atypical cases into the following three groups. Group 1: refractory epilepsies beginning in early infancy, associated with atypical electroencephalographic (EEG) features; Group 2: generalized epilepsies with spasms in clusters at ages of 2-3 years or above; and Group 3: localization-related epilepsies with spasms in clusters. Ictal clinical and EEG findings of spasms in clusters in these atypical patients and also those in WS are similar. Patients in Group 1 often suffer from Aicardi syndrome, cortical malformations, early myoclonic encephalopathy and Ohtahara syndrome. Most patients in Group 2 suffer from Lennox-Gastaut syndrome and other generalized epilepsies such as severe epilepsy with multiple independent spike foci. A significant number of them had a history of WS. Small number of patients in Group 2 can be diagnosed as having late-onset WS or long-lasting WS. In Groups 1 and 3 patients, cortical mechanisms play a critical role in their pathophysiology. The presence of older patients with spasms in clusters might indicate not only developing process of the brain but also some selective dysfunction of the brain plays an important role in the occurrence of spasms in clusters. Investigations on these atypical patients can help the understanding of pathophysiological mechanisms of WS and its related epileptic syndromes.

Suppression-burst patterns in intractable epilepsy with focal cortical dysplasia

We report on a patient with early-onset spasms in series and partial seizures associated with focal cortical dysplasia whose EEGs showed suppression-burst patterns during early infancy. These electroclinical characteristics suggested a diagnosis of Ohtahara syndrome, but the EEG findings were atypical because of the lack of suppression-burst patterns during wakefulness. In addition, the patient did not have severe psychomotor retardation. With high-dose pyridoxal phosphate therapy, seizures were suppressed and suppression-burst patterns disappeared at 2 months of age. Focal motor seizures recurred later and they often evolved into epilepsia partialis continua. Patients with early-onset intractable seizures associated with suppression-burst patterns on EEGs have several different etiologies, and these patients should be categorized according to their etiology in addition to their syndromic diagnosis.