Hemimegalencephaly and intractable epilepsy: benefits of hemispherectomy

Hemimegalencephaly without seizures: report of a case and review of literature

Hemimegalencephaly is a rare malformation of the brain characterized by enlargement of one cerebral hemisphere. The classic clinical triad consists of intractable epilepsy, severe psychomotor delay and hemiparesis. We report a case of a six months old girl, with the radiological features of hemimegalencephaly but with a comparatively benign clinical course. She had mild developmental delay but with no paresis or seizures. Literature revealed only two reported cases of hemimegalencephaly without the presence of seizures. We discuss the clinical and radiological findings of this third reported case.

Epileptic spikes in Rasmussen's encephalitis: Migratory pattern and short-term evolution. A MEG study

OBJECTIVE

We aimed this study at identifying cortical areas involved in the generation of interictal spikes in Rasmussen's Encephalitis (RE) patients using magnetoencephalography (MEG), at comparing spike localization with the degree of cortical atrophy detected by MRI, and at identifying short-term changes during the follow-up.

METHODS

Five patients with RE underwent two MEG and magnetic resonance imaging (MRI) (six months interval). The sources of visually detected spikes were estimated using equivalent current dipoles technique; these were then superimposed on individual MRI and clustered; the locations of the clusters were related to the MRI stage of cortical atrophy.

RESULTS

All patients showed spikes and clusters located in different cortical areas in both recordings; the locations had a limited correspondence with cortical atrophy. The second recordings showed changes in the localisation of spikes and clusters, and confirmed the dissimilarities with neuroradiological abnormalities.

CONCLUSIONS

The presence of clusters of spikes of variable localisation suggests that RE progresses in a multifocal and fluctuating manner. The cortical areas most involved in epileptogenesis did not completely coincide with the most atrophic areas.

SIGNIFICANCE

MEG can contribute to evaluating multifocal hemispheric spikes in RE and to better understand the time course of epileptogenic process.

Hemispherectomy for Hemimegalencephaly Due to Tuberous Sclerosis and a Review of the Literature

BACKGROUND

Hemimegalencephaly with tuberous sclerosis complex is an uncommon association, usually associated with intractable seizures that begin in the neonatal period or early infancy. Typically, the seizures are managed with medications until the patient is older when surgical treatment is considered safe.

PATIENT DESCRIPTION

We describe a 7-week-old infant with tuberous sclerosis (TSC1 mutation) and hemimegalencephaly who underwent a functional hemispherectomy for status epilepticus. No clinical seizures have occurred since surgery nearly 5 years ago and subsequent weaning of antiepileptic drugs 3 years ago. This is one of the youngest patients with tuberous sclerosis complex treated with a hemispherectomy and one of seven patients described in the literature.

CONCLUSIONS

Our patient, along with previously reported cases, suggests that a hemispherectomy is a viable option in the very young. With evolution of this surgical process since its inception nearly 6 decades ago, it may now be performed safely in early infancy, engendering the possibility of seizure freedom in most and thus optimizing neurodevelopmental outcome.

Hemispherotomy in an infant with hemimegalencephaly

Hemimegalencephaly (HME) is a rare hamartomatous congenital malformation of the brain. The epilepsy pattern in HME can be partial seizures or may present as spasms as in epileptic encephalopathy. Epilepsy associated with HME is usually resistant to antiepileptic drugs and requires surgical intervention. Hemispheric disconnection has been reported to be efficient in seizure control and prevents further cognitive injury and developmental delay. We report a case of HME, who underwent a two-stage hemispherotomy due to complications in the first surgery. She had more than 90% reduction of seizures with good developmental outcome on follow-up. Thus, despite risks of the procedure, early surgery should be preferred in infants with HME.

Surgery for posterior quadrantic cortical dysplasia. A review

BACKGROUND

Posterior quadrant dysplastic lesions represent 3-15 % of multilobar cortical developmental pathologies, 3-5 % of all the indications to surgery for epilepsy resistant to medical treatment.

OBJECTIVE AND METHODS

The objective of this study is to review the pertinent literature related to the presurgical clinical, neurophysiological, and neuroradiological evaluation of children affected by posterior quadrant dysplasia in order to discuss the intraoperative management and the different surgical techniques that have been proposed to treat this condition as well as factors related with postsurgical seizure outcome.

RESULTS AND CONCLUSIONS

Seizures appear most commonly in infants and rapidly progress to a catastrophic course. They are mostly represented by focal seizures and spasms. Surface interictal video-EEG is characterized by background flattening and paroxysmal discharges prevalent on the affected side but not unusually extending to the controlateral hemisphere. The last occasionally shows an independent irritative activity in spite of the absence of further visible structural abnormalities. Most of the patients have visual field or visual attention deficits at diagnosis. Resective as well as disconnective surgical procedures have been proposed for the management of this condition, none of them having shown clear advantages in terms of seizure outcome and complications. Intraoperative electrocorticography (EcoG) and sensorimotor monitoring have been successfully used to improve the localization of the epileptic focus and reduce surgical complication rates. Undistincted lesion borders, independent controlateral ictal or/and interictal EEG activity, and incomplete resections/disconnections are among the main factors that have resulted to be associated with a worse seizure outcome.

Hemimegalencephaly without epilepsy: case report

Hemimegalencephaly is a rare sporadic brain malformation characterized by enlargement of one cerebral hemisphere. The classical clinical triad consists of intractable epilepsy, severe psychomotor delay and hemiparesis. In this report, we describe a case of a 3-year-old girl, with all the radiological features of severe hemimegalencephaly but with a comparatively benign clinical course. She had no hemiparesis, mild delay and no seizures. An extensive literature review reveals only one previously reported case of hemimegalencephaly with the absence of seizures, as part of case series. This is the first dedicated case report, with clinical description and radiological images, of this entity.

Epilepsy surgery for hemispheric syndromes in infants: hemimegalencepahly and hemispheric cortical dysplasia

OBJECTIVE

Hemimegalencepahly (HME) and Hemispheric Cortical Dysplasia (HCD) are rare congenital diseases that occur with intractable epilepsy. They manifest by early epilepsy, mental retardation, hemianopsia and contralateral hemiplegia. Hemispheric disconnection (mainly anatomical hemispherectomy, peri-insular hemispherotomy, modified lateral hemispherotomy and vertical parasagittal hemispherotomy) have been reported to be efficient on seizures and also to prevent additional cognitive injury and developmental delay.

METHOD

We reviewed literature about clinical presentation, predictors of outcome and expectation about epileptic seizures and cognitive outcome.

RESULTS

Clinical presentation and seizures outcome have been described in almost 600 children for the last thirty years. Epilepsy improved in most cases depending on the series and the follow-up duration. Percentage of seizure-free patients with HME or HCD was lower than in other groups (Rasmussen Encephalitis, Vascular Sequellae). Post-operative complications decreased with the hemispherotomy surgical procedures. EEG abnormalities on the "save" hemisphere did not negatively influence postsurgical outcome. Seizure free outcome did not seem to depend on the surgical procedure but the presence of residual insular cortex seemed to be associated with persistent postoperative seizures. Contralateral MRI abnormalities seemed to be associated with poorer prognosis for seizure free outcome and lack of cognitive improvement.

CONCLUSION

Hemispheric disconnection remains the best treatment in order to control epileptic seizures. Hemispheric surgical procedures are safe and can be performed from the first month of life. Prospective studies of cognition are needed to emphasize benefits on long term outcome.

Diffusion tensor imaging and fiber tractography in brain malformations

Diffusion tensor imaging (DTI) is an advanced MR technique that provides qualitative and quantitative information about the micro-architecture of white matter. DTI and its post-processing tool fiber tractography (FT) have been increasingly used in the last decade to investigate the microstructural neuroarchitecture of brain malformations. This article aims to review the use of DTI and FT in the evaluation of a variety of common, well-described brain malformations, in particular by pointing out the additional information that DTI and FT renders compared with conventional MR sequences. In addition, the relevant existing literature is summarized.

Hemimegalencephaly accompanied by myoclonic status epilepticus

We describe a boy (aged 2 years and 7 months) with hemimegalencephaly who developed myoclonic status, which improved dramatically after total callosotomy. The patient experienced seizures beginning at age 2 days, at which time electroencephalography revealed a right unilateral burst suppression pattern, and cranial magnetic resonance imaging revealed an enlarged right hemisphere. At age 8 months, habitual seizures increased to more than daily frequency. At the same time, myoclonic status epilepticus appeared with frequent erratic, partial, massive myoclonic seizures and clouding of consciousness. These signs were accompanied by diffuse spike and spike-wave patterns on electroencephalography, indicating myoclonic status in nonprogressive encephalopathy. Total callosotomy performed at age 10 months resulted in the complete disappearance of myoclonic status and prominent decrease in habitual seizures. This description of hemimegalencephaly is the first, to our knowledge, in which total callosotomy alleviated myoclonic status epilepticus. Although the mechanism of myoclonic status epilepticus remains unknown, our results suggest that cortico-cortical pathways are involved in this type of myoclonic status.

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.

Interictal epileptogenic fast oscillations on neonatal and infantile EEGs in hemimegalencephaly

PURPOSE

Hemimegalencephaly is an epileptic encephalopathy which presents during the neonatal period. Our aims are to analyze interictal fast oscillations and EEG patterns in neonates and infants with hemimegalencephaly.

METHODS

We collected scalp EEGs and applied multiple band frequency analysis (MBFA) to analyze frequency and power of interictal fast oscillations (FOs).

RESULTS

We studied 18 scalp EEGs in 7 patients with catastrophic epilepsy secondary to hemimegalencephaly, between 3 days and 24 months of age. Maximum frequency of FOs (22-57 Hz; mean, 42 Hz) on the hemimegalencephalic side was significantly higher than those (8-27 Hz; mean, 18 Hz) in the unaffected side (p<0.05). Differences in maximum FOs remained within 1-8 Hz (mean, 3 Hz) across consecutive EEGs. We found four EEG patterns: (1) suppression burst pattern (7 EEGs, 6 patients), (2) continuous triphasic complex pattern (5 EEGs, 3 patients), (3) continuous high amplitude slow waves with spikes (3 EEGs, 2 patients) and (4) frequent spike and slow waves (3 EEGs, 2 patients). Five patients with multiple EEG recordings showed changing EEG patterns.

CONCLUSION

We confirmed the interictal epileptogenic FOs in neonatal EEGs of patients with hemimegalencephaly. The frequency of epileptogenic FOs remains stable from the neonates through increasing age while the patterns of EEG changed during brain maturation.

Longitudinal CT and MR appearances of hemimegalencephaly in a patient with tuberous sclerosis

CASE REPORT

A 3-day-old baby was referred to our institution with seizures since birth and a presumptive diagnosis of cerebral tumor detected by prenatal ultrasound. Computed tomography (CT) and Magnetic Resonance (MR) imaging performed immediately after birth revealed the presence of an enhancing mass in the left cerebral hemisphere.

DISCUSSION

The possibility of a congenital malignant brain tumor was considered. Although surgery was advised, the parents opted for conservative medical management. The infant was under treatment for seizures with antiepileptic drugs. At 7-month follow-up, there was a noticeable increase in the seizure activity with signs of developmental delay and increased head circumference. Repeat CT and MR imaging showed features of hemimegalencephaly with a calcified mass involving the left hemisphere. The patient was diagnosed to have tuberous sclerosis. This case report illustrates how an enhancing mass (possibly a tuber) over a period of time diminishes in size and becomes calcified in a patient with tuberous sclerosis and associated hemimegalencephaly.

Hemispherectomy in a premature neonate with linear sebaceous nevus syndrome

A male neonate with seizures, linear sebaceous nevus syndrome and hemimegalencephaly underwent hemispherectomy at 36 weeks' gestational age. He has had no clinical seizures in the 13 months since surgery but continues to have sharp wave activity over some parts of the intact hemisphere. He has moderate developmental delay and a mild hemiparesis but is making developmental progress.

Malformations corticales et épilepsie : apport de l’IRM

Malformations of cortical development are increasingly recognized as important causes of epilepsy, developmental delay and other neurological disorders. Our purpose is to present the relevance of the MRI in these pathologies with the clinical, genetic and therapeutic aspects. This classification is based on the three fundamental events of cortical formation: proliferation of neurons and glie in the periventricular zone, migration of postmitotic neurons to the periphery, subsequent cortical organization. MR analysis evaluates particularly the cortical thickness, sulcal and cortical morphology, gray-white matter junction, and looks for gray matter in abnormal location. These data coupled with the familial history, the seizure characteristics and genetic findings should allow an appropriate classification of the lesions. MR imaging allows the detection and classification of cortical malformations. MR imaging findings are primordial to consider surgery when the epilepsy becomes refractory to the anti-epileptic drugs. An adequate classification of these malformations should help to provide to the family an appropriate counseling both in terms of genetics and outcome.

Epidemiology of hemimegalencephaly: a case series and review

Hemimegalencephaly (HME) is a congenital brain malformation characterized by unilateral enlargement of the cerebral hemisphere. Clinically, HME is typically associated with hemiparesis, psychomotor retardation, and intractable seizures usually apparent soon after birth. HME is often an isolated finding, but it has been described as an occasional feature of a large number of syndromes, many of which may not be readily identified at birth. There are a multitude of case series and reports of HME in the English literature; however, there is no comprehensive, unbiased, detailed survey characterizing the proportion of cases of HME that are associated with a syndrome. We performed a retrospective study of all cases of HME seen at our institution from 1990 to 2003. Of the 15 cases of HME identified, 53% (8/15) were non-syndromic and 47% (7/15) of the cases were associated with a known or suspected genetic syndrome. In patients with syndromic HME, many of the syndromic features were not readily discernible at birth or in early infancy. It is, therefore, imperative to continually evaluate any infant with HME for signs and symptoms of these and other syndromes. Knowing the relative differential diagnosis will lead to a more comprehensive evaluation, improvement in expectant management, and appropriate counseling of families before considering radical surgical options such as hemispherectomy.

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.

Neuronal migration disorders, genetics, and epileptogenesis

Several malformation syndromes with abnormal cortical development have been recognized. Specific causative gene defects and characteristic electroclinical patterns have been identified for some. X-linked periventricular nodular heterotopia is mainly seen in female patients and is often associated with focal epilepsy. FLN1 mutations have been reported in all familial cases and in about 25% of sporadic patients. A rare recessive form of periventricular nodular heterotopia owing to ARGEF2 gene mutations has also been reported in children with microcephaly, severe delay, and early-onset seizures. Lissencephaly-pachygyria and subcortical band heterotopia represent a malformative spectrum resulting from mutations of either the LIS1 or the DCX (XLIS) gene. LIS1 mutations cause a more severe malformation posteriorly. Most children have severe developmental delay and infantile spasms, but milder phenotypes are on record, including posterior subcortical band heterotopia owing to mosaic mutations of LIS1. DCX mutations usually cause anteriorly predominant lissencephaly in male patients and subcortical band heterotopia in female patients. Mutations of the coding region of DCX were found in all reported pedigrees and in about 50% of sporadic female patients with subcortical band heterotopia. Mutations of XLIS have also been found in male patients with anterior subcortical band heterotopia and in female patients with normal brain magnetic resonance imaging. The thickness of the band and the severity of pachygyria correlate with the likelihood of developing severe epilepsy. Autosomal recessive lissencephaly with cerebellar hypoplasia, accompanied by severe delay, hypotonia, and seizures, has been associated with mutations of the reelin (RELN) gene. X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia in genotypic males is associated with mutations of the ARX gene. Affected boys have severe delay and infantile spasms with suppression-burst electroencephalograms. Early death is frequent. Carrier female patients can have isolated corpus callosum agenesis. Schizencephaly has a wide anatomoclinical spectrum, including focal epilepsy in most patients. Familial occurrence is rare. Initial reports of heterozygous mutations in the EMX2 gene have not been confirmed. Among several syndromes featuring polymicrogyria, bilateral perisylvian polymicrogyria shows genetic heterogeneity, including linkage to chromosome Xq28 in some pedigrees, autosomal dominant or recessive inheritance in others, and an association with chromosome 22q11.2 deletion in some patients. About 65% of patients have severe epilepsy. Recessive bilateral frontoparietal polymicrogyria has been associated with mutations of the GPR56 gene.

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.

[Early functional hemispherectomy in hemimegalencephaly associated to refractory epilepsy]

Hemimegalencephaly (HME) is a rare congenital brain malformation of unknown etiology. Patients with HME can present with an early onset epileptic syndrome which is often refractory to medical treatment and associated to impaired neurological development. Functional hemispherectomy (FH) has proven to be a valuable treatment alternative in patients with refractory epilepsy in this setting. Very few children operated under the age of 6 months and bearing HME and catastrophic epilepsy (CE) have been described in the literature. This study reports on 2 kids younger than 6 months with HME and CE submitted to FH with good clinical outcome.

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.

Treatment of Refractory Status Epilepticus with Hemispherectomy

A 7-year-old boy with left hemiparesis secondary to right hemispheric cortical dysplasia was admitted to the hospital with increasing numbers of seizures. Magnetic resonance imaging showed a small dysplastic right hemisphere with abnormally thickened gyri and an apparently normal left hemisphere. Previous video-electroencephalogram (EEG) monitoring showed bilateral independent spikes and generalized slow spike-and-wave episodes on EEG and [18F]fluorodeoxyglucose (FDG) positron emission tomography scan demonstrated scattered areas of regional hypometabolism bilaterally; therefore hemispherectomy was not undertaken at that time. During this hospital stay, nonconvulsive status epilepticus developed and was refractory to multiple medical therapies including pentobarbital (PTB) coma. Burst-suppression pattern during PTB coma appeared to be generalized spike and wave, but when EEG was reviewed with increased time resolution spikes suggested a right hemisphere origin. The patient underwent bilateral intracarotid amobarbital spike-suppression test that showed only minimal suppression of epileptiform discharges with injection of the left carotid, but complete suppression of spike activity after right-sided carotid injection. A right hemispherectomy was performed with complete cessation of status epilepticus. Postoperative EEG showed no epileptiform discharges. Patient follow-up was limited to 12 months after surgery. The patient had regained the ability to walk unaided and was seizure free with a single antiepileptic medication. This case illustrates a potentially life-saving procedure for refractory status epilepticus and several techniques including a spike-suppression test to aid in prediction of cessation of seizures after hemispherectomy.

Indications for surgical treatment of epilepsy in childhood: a clinical and neurophysiological approach

Resistant epilepsy is defined as the persistence of unacceptable seizures, despite correct drug treatment, or control of seizures at the cost of excessive side effects. About 30% of partial seizures are resistant to treatment; many of them is potentially a candidate for surgical treatment. Selection of patients is based fundamentally on precise identification of the epileptogenic area and on the evaluation that possible removal of that area will not be followed by serious neurological or neuropsychological deficits, or by onset of seizures in another part of the brain. To this end, careful clinical, neurophysiological and functional studies are conducted. Compared with adults, video-electroencephalographic (EEG) study of seizures in childhood is more difficult because of the lack of patient cooperation and, therefore, the lack of every subjective element in the seizures. Furthermore, the criteria for defining drug resistance in childhood are still under discussion, as many epilepsies are age dependent and seizures stop with growth. Despite this, the age at time of surgery has been steadily decreasing, in the conviction that the persistence of intractable partial epilepsy is detrimental to cognitive development and can damage brain areas that are apparently healthy. The clinical and EEG criteria for epilepsies that are secondary to some specific disorders have been defined, e.g. hemimegalencephalia and focal cortical dysplasias often produce epilepsy with onset in the first days of life characterized by partial seizures and subintrant spasms, EEG record of focal or hemispheric burst suppression and drug resistance that can be defined within the first months of life. Prolonged video-EEG monitoring is always necessary to establish congruence between the area in which the seizure originates and the brain lesion evidenced at neuroimaging. Correct monitoring of seizures means close cooperation between neurologist, neurophysiology technician and the patient, if the child is at least 5-6 y old. Absence of cooperation also limits the use of in-depth recording. Neuropsychological assessment of the child can be of great help in defining the area damaged by the epileptogenic site as well as the state of the other brain areas. Close cooperation between neurologist, radiologist, neuropsychologist and brain surgeon is necessary for a case-by-case assessment of indication for surgical treatment.

Hemimegalencephaly: part 2. Neuropathology suggests a disorder of cellular lineage

Cerebral tissue from hemispherectomy in three children (two 4-month-old girls and one 4-year-old boy) with hemimegalencephaly was studied using histochemical and immunocytochemical markers of neuronal and glial maturation and identity. Histologic abnormalities of cellular growth and cytomorphology, including "balloon cells," were present in both gray and white matter, in addition to disorganized tissue architecture. Cells in the mitotic cycle were absent. Many hypertrophic, atypical cells with enlarged processes exhibited mixed or ambiguous lineage, with immunoreactivity for both glial (glial fibrillary acidic protein [GFAP]; S-100beta) and neuronal proteins (microtubule-associated protein 2 [MAP2], neuronal nuclear antigen, chromogranin A, and neurofilament protein [NFP]). Strong vimentin reactivity was present in neurons, as well as glial cells and cells of mixed lineage, suggesting incomplete maturation. Synaptophysin-reactive axons terminated on a minority of balloon cells and on most heterotopic single neurons in white matter, confirmed by electron microscopy, demonstrating that single heterotopic neurons are not synaptically "isolated," as they may appear; thus, they are capable of contributing to epilepsy. Oligodendrocytes are the least affected cells, at least in some cases. The findings are reminiscent of the hamartomas of tuberous sclerosis. We conclude that hemimegalencephaly is a primary disorder of neuroepithelial lineage and cellular growth. A migratory disturbance contributes to disorderly tissue architecture but is secondary. No pathologic difference is detected between isolated and syndromic forms of hemimegalencephaly.

Childhood-onset epilepsy associated with polymicrogyria

To study the electroclinical characteristics of patients with childhood-onset epilepsy who showed polymicrogyria (PMG) on MRI, we classified 15 patients according to the location of PMG on MRI. The composition of the subjects was as follows: four patients with PMG in both hemispheres; three with localized PMG in one hemisphere associated with other lesions such as porencephaly; and eight with only localized PMG in one hemisphere. We investigated the electroclinical characteristics of the epileptic syndromes associated with these different types of PMG. Four patients suffered from infantile spasms during their clinical course. Five patients suffered from epilepsy with electrical status epilepticus during slow sleep (ESES) and ESES-related epilepsy. The other six patients had only localization-related epilepsy throughout their clinical course. Patients with PMG in both hemispheres, and localized PMG in one hemisphere associated with other lesions tended to have early-onset intractable seizures, especially infantile spasms. On the other hand, patients with only localized PMG in one hemisphere had ESES and ESES-related epilepsy or localization-related epilepsy, and their seizure prognosis was relatively favorable. These findings are useful in predicting the outcome of patients with PMG.

Clinical study of catastrophic infantile epilepsy with focal seizures

This study investigated clinico-electrical and etiologic characteristics of catastrophic infantile epilepsy with focal seizures developed in early infancy. The patients included 15 children who fulfilled the following criteria: seizure onset before 12 months of age, presence of daily focal or secondarily generalized seizures resistant to antiepileptic drugs for at least 3 months, and exclusion of Ohtahara and West syndromes. Patients were classified into three subgroups. Three patients demonstrated progressively deteriorating neurologic symptoms associated with progressive cerebral atrophy and multifocal seizure onset. Three other children were characterized by hemiparesis and exclusively lateralized seizure onset because of focal cortical dysplasia in the contralateral hemisphere. The remaining nine children did not demonstrate any rapidly progressive neurologic deterioration or increasing cerebral atrophy and exhibited multifocal seizure onset. At the last examinations, all except one patient demonstrated moderate to severe psychomotor retardation. Catastrophic infantile epilepsy with focal seizures tended to demonstrate multifocal seizure onset and a deleterious clinical course with numerous focal seizures regardless of etiology. Because migratory focal seizures appear to be common in these infants, we have to search for the underlying etiopathogenesis of these patients, including not only metabolic errors but also localized or lateralized structural abnormality.

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.

Postoperative development of children after hemispherotomy

We studied the postoperative development of 14 children with cortical dysgenesis who underwent modified functional hemispherectomy (hemispherotomy) at the age of 6 years or younger. At follow-up of 24-72 months (median of 47 months), six (43%) were seizure-free, six achieved>90% reduction, one achieved 50-90% reduction, and one achieved 0-50% reduction in seizure frequency. At the preoperative and final postoperative examinations, mean scores of developmental quotient (DQ) were as follows: 25.5 and 31.9 in total DQ, 26.0 and 33.7 in intellectual DQ, and 27.4 and 22.9 in motor DQ. Children scoring >50 points in preoperative intellectual DQ score obtained near-normal intellectual DQ postoperatively, while, those scoring <10 DQ preoperatively remained at a low developmental level. Among children with DQ scores in the range from 10 to 50, two children who obtained seizure-free outcome and were operated upon in the first 3 years of life achieved marked developmental progress. The present study indicated that high preoperative intellectual DQ and cessation of seizures seem to be associated with better postoperative intellectual development. However, long-term observation of postoperative development and an accumulation of more cases will be needed before we can reach a firm conclusion.

Surgery for hemispheric malformations of cortical development

The treatment of patients with hemispheric malformations of cortical development presents a challenging clinical problem that often requires surgical intervention. The development of a safe and effective treatment strategy for these patients requires an extensive work-up with a great deal of attention to a variety of multidisciplinary testing methods. In this article, the authors describe the presurgical evaluation of patients with hemispheric malformations of cortical development and epilepsy and review the surgical techniques currently available. They also detail some of the controversial issues regarding surgical treatment of these patients.

Epileptic seizures and syndromes

This article describes the main characteristics of the different types of seizures and their classifications. The main types of epilepsies are reviewed, including their main, clinical, and EEG features and an overview of their treatment.

Surgical indication for refractory childhood epilepsy

Recent progress in surgical intervention for medically refractory epilepsy has helped to shed light on more complex epileptogenic problems in children and infants. Surgical treatment increasingly is being used in pediatric patients, but the indications for surgery in this age group have not been well defined. The developing child with a seizure disorder has several problems that are different from adults, such as neural plasticity, deleterious effects of seizures on developmental status, and spontaneous resolution of epilepsy. The critical age for irreversible brain dysfunction and the timing of surgery are the main issues for the treatment of children. Thus, earlier surgical intervention is generally recommended to prevent further detrimental seizure effects, but we still do not know the optimal age. Until the establishment of guidelines for pediatric epilepsy surgery, surgical indications should be determined by the prognosis and the presence of a resectable epileptogenic focus, which in turn are based on the localization of the epileptic focus, seizure frequency, severity, and cognitive function of each case, rather than just the patient's age.

Malformations of cortical development and epilepsy

Although once thought to be rare, malformations of cortical development are being increasingly recognized as the underlying cause of developmental delay in children and of epilepsy in children and young adults. Advances in neuroimaging and developmental neurobiology have created the tools by which these important malformations have been investigated. Through a symbiotic type of relationship, these investigations, and the search for a better understanding of these malformations, have led to advances in neuroimaging techniques and better understanding of both normal and abnormal brain development. In this review, the most common malformations or cortical development associated with epilepsy are discussed in regard to their clinical manifestations, classification, imaging appearance and basic neurobiology.

Epilepsy and Cortical Dysplasias

Focal cortical dysplasias (FCD) and diffuse cortical dysplasias (DCD) are a heterogeneous group of disorders defined by abnormal cerebral cortical cytoarchitecture that are associated with epilepsy. Patients with either DCD or FCD may suffer from a variety of epilepsy subtypes and these are often refractory to most anti-epileptic drugs (AEDs) despite polytherapy. The etiologies of cortical dysplasias (CD) are diverse, and include inherited genetic syndromes such as Miller-Dieker or X-linked lissencephaly, subcortical band heterotopia, and the tuberous sclerosis complex, as well as nongenetic exogenous insults such as hypoxic-ischemic injury, viral or other type of central nervous system infection, or traumatic injury. A large number of FCD cases are idiopathic and very small regions of FCD (microdysgenesis) are now being identified in resected epilepsy specimens. Recent data suggests that nearly 30% of epilepsy specimens evaluated histologically will contain regions of overt or microscopic CD. The mainstay of appropriate therapy for CD remains the standard AEDs or epilepsy surgery. In too few disorders, specific AEDs provide therapeutic advantage in the setting of individual forms of CD. The ketogenic diet may provide seizure control in a subpopulation of patients. In both DCD and FCD, surgical resection can be curative in the appropriately selected patients. Surgical approaches include focal neocortical resections, temporal lobectomy, or larger hemispheric resection procedures.

Cortical reorganization in linear nevus sebaceous syndrome: a multimodality neuroimaging study

The authors report the findings of multimodal structural, functional, and metabolic imaging in a patient with linear nevus sebaceous syndrome, intractable seizures, and right megalencephaly. Despite nearly continuous paroxysmal electrical activity from the megalencephalic region, imaging studies suggested nonfunctional tissue in this region with reorganization of cortical function to the unaffected ipsilateral hemisphere. Hemispherectomy has been successfully performed in previous patients; however, it could have led to marked left hemiparesis with significant functional morbidity in this patient because of ipsilateral reorganization of the primary motor cortex.

Epilepsy surgery in infancy

Surgery for intractable epilepsy is being offered at progressively younger ages, including infancy. The most common causes of catastrophic epilepsy in very young surgical candidates are focal malformations of cortical development and low-grade tumors. Additional causes include Sturge-Weber syndrome, epidermal nevus syndrome, hemimegalencephaly, and prenatal or perinatal infarction. Many infants manifest with focal seizures, whereas some patients have infantile spasms in the setting of a focal epileptogenic lesion. Video electroencepholography, magnetic resonance imaging, and positron emission tomography are critical investigations to explore surgical options. In small series, the percentage of infants free of seizures after surgery was in the range of 60%. This is similar to that seen after epilepsy surgery in older children, adolescents, and adults. However, larger series with long-term follow up will be important. Furthermore, the extensive procedures required in infants for removal of the epileptogenic developmental lesions entail some risk, and should not be offered in the absence of severe epilepsy. Most infant candidates for epilepsy surgery have significant developmental delay. Few data are available, but anecdotal experience suggests that surgical relief of catastrophic epilepsy may result in resumption of developmental progression. For each infant, the timing of surgery must be carefully considered based on full assessment of the relative risks and benefits, derived from a detailed presurgical evaluation.

Clinical spectrum of cortical dysplasia in childhood: diagnosis and treatment issues

Disorders of cortical development form a spectrum of lesions produced by insults to the developing neocortex. These conditions typically first manifest in childhood with epilepsy, developmental delay, and focal neurologic signs. Although the clinical and electrophysiologic findings are often nonspecific, high-resolution magnetic resonance imaging facilitates diagnosis during life, and assists in delineating specific clinical syndromes. While many patients are dysmorphic and severely affected by mental retardation and epilepsy, some have normal or near-normal cognitive function and no seizures. Molecular studies of dysplastic cortex are providing new insights into the basic mechanisms of brain function and development, while pathologic analysis of tissue removed at surgery is helping to define epileptic circuitry. Treatment of the epilepsy associated with cortical dysplasia is often frustrating, but surgical approaches based on accurately defining epileptogenic regions are proving increasingly successful. Genetic diagnosis is important for accurate counseling of families.

Evaluation of gross and fine motor functions in children with hemidecortication: predictors of outcomes and timing of surgery

The purpose of this study is three-fold: First, to determine the levels of gross and fine motor functions in children before and after hemidecortication, using standardized measurement tools; second, to investigate if predictors of these outcomes can be characterized; and third, to explore if both clinical measures and functional magnetic resonance imaging (MRI) potentially can identify optimal timing of surgery. The Gross Motor Function Measure and the Quality of Upper Extremity Skills Test are shown to be comprehensive, standardized outcome measures of movement performance in affected children. Age at surgery and interval between age at seizure onset and age at surgery could be the most reliable predictors of clinical outcomes. Functional MRI studies are valuable in exploring the potential of the cortical reorganization that sustains residual sensorimotor function. The combination of clinical measures with functional MRI is a promising method of inquiry into developmental and plasticity processes.

Electroclinical characteristics of hemimegalencephaly

Presented here are two long-term follow-up patients with hemimegalencephaly. Patient 1 had Ohtahara's syndrome, which evolved into West's syndrome. Patient 2 had localization-related epilepsy, which demonstrated epilepsia partialis continua throughout the clinical course. The patients' interictal electroencephalograms revealed asymmetric suppression-burst patterns sometime during the clinical course: only during early infancy in patient 1 and until the last follow-up (at 30 years of age) in patient 2. Both patients had moderate mental and motor disturbances with persistence of seizures. Hemiplegia was progressive during early childhood. Aggravation of hemiplegia might be related to frequent seizures and persistent electroencephalographic abnormalities during early childhood. Although asymmetric suppression-burst patterns are considered characteristic electroencephalographic findings in these cases, the duration of their appearance did not have definite prognostic significance.

Linear epidermal nevus and nevus sebaceus syndromes: a clinicopathologic study of 3 patients

BACKGROUND

Linear epidermal nevus syndrome and linear sebaceus nevus syndrome are rare neurocutaneous syndromes characterized by epidermal nevi, epilepsy, and mental retardation. Pathologic descriptions of the central nervous system findings in such patients are rare.

DESIGN

We examined the clinicopathologic features of 2 patients with linear epidermal nevus syndrome and 1 with nevus sebaceus syndrome who underwent surgical resections for chronic epilepsy in a tertiary referral center with a high volume of epilepsy surgery.

RESULTS

Patients included 3 females, aged 11 months (patient 1), 8 years (patient 2), and 2 1/2 years (patient 3) at the time of surgery. The duration of seizures prior to surgery was 11 months, 6 years, and 28 months, respectively. Two patients had epidermal nevi involving the head region (patients 1 and 3), and 1 had a nevus sebaceus of Jadassohn (patient 2); patient 2 had a choristoma, and patient 3 had a dermoid cyst in the eye region. Patient 1 demonstrated hemimegalencephaly radiographically. Histologic examination of resected cortical tissue in patients 1 and 2 demonstrated severe diffuse cortical dysplasia characterized by a disorganized cortical architectural pattern, a haphazard orientation of cortical neurons, and increased molecular layer neurons. Gyral fusion was seen in patient 1. Pial glioneuronal hamartomas were observed in patient 1. Prominent cortical astrocytosis was seen in patients 1 and 2, and foci of microcalcification were evident in patient 1. Cortical dysplasia was milder in patient 3 and consisted of an increased number of molecular layer neurons. Neuronal heterotopia was observed in all 3 patients.

CONCLUSION

The spectrum of neuronal migration abnormalities in the setting of these syndromes may be variable in terms of its histologic phenotypic manifestations.

Surgical treatment of epilepsy in children

In carefully selected children, as well as adults, intractable seizures may be eliminated or greatly reduced by cortical resection or hemispherectomy. Critical features of surgical candidacy include intractable disabling epilepsy, a localized epileptogenic zone, and a low risk of new postoperative deficits; however, the analysis may be complicated in children. Compared with adults, pediatric patients are especially likely to present with poorly localizing electroencephalographic features because of their high incidence of extratemporal localization and developmental pathology. Maturation factors may result in unusual epilepsy manifestations, for example, infantile spasms and hypsarrhythmia caused by a focal cortical lesion. The cognitive and psychosocial costs of continued frequent seizures during infancy and childhood must be assessed differently from those in adults and may include stagnation of developmental progression. The risk for new postoperative deficits may be modified if surgery is performed during stages of active brain maturation with developmental plasticity. For each individual child, the potential risk/benefit ratio for surgery must be carefully weighed on the basis of results of an extensive preoperative evaluation. Results from pediatric epilepsy surgery series are encouraging, with percentages of seizure-free patients similar to those in adult series. In some series, delaying surgery for childhood-onset epilepsy into adulthood was associated with greater permanent psychosocial, behavioral, and educational problems. The available data suggest that children should be considered for surgical evaluation at whatever age they present with severe intractable localization-related epilepsy. Complicated cases warrant referral to specialized centers with extensive pediatric epilepsy surgery experience.

The linear naevus sebaceus syndrome

The linear naevus sebaceus syndrome (LNSS) is a phakomatosis, characterized in general by a triad consisting of naevus sebaceus of Jadassohn, seizures, and mental retardation. In addition, a broad spectrum of neurological, ophthalmological, skeletal, urogenital and cardiovascular symptoms may be encountered. According to our literature review, seizures and mental retardation were reported in 67 and 61% of cases, respectively. Because ophthalmological abnormalities (59%) and involvement of other organ systems (61%) occur frequently, we advise avoidance of adhering to the classical triad for recognizing or describing LNSS. Gross structural abnormality of the cerebrum or cranium was frequently observed (72%), consisting mainly of enlargement of one lateral ventricle, hemimegalencephaly and hemimegacranium. We report a case of a male patient with the clinical features of LNSS, but without cerebral developmental abnormalities at autopsy examination.

Study on surgical treatment of intractable childhood epilepsy

We studied the clinical details of 14 children with intractable epilepsies, all of whom underwent epilepsy surgery before age 18 years. All 14 suffered catastrophic seizures, which were resistant to the full range of available medical treatments. The ages at operation ranged from 4 years 7 months to 17 years 2 months, with a mean of 9 years 11 months. In nine patients, the age at onset of epilepsy was less than 2 years. The seizure disorders were classified as temporal lobe epilepsy in two patients, extratemporal lobe epilepsy in 10, and symptomatic generalized epilepsy in two. Eight patients had a hemicorporeal deficit (hemiparesis or hemiplegia) preoperatively. All 14 patients showed localized magnetic resonance imaging (MRI), single photon emission computer tomography (SPECT) and/or positron emission tomography (PET) abnormalities, providing crucial information regarding the epileptic focus. As to the surgical outcomes, four patients became seizure-free and the other 10 showed significant improvement during a mean follow-up period of 2 years 5 months. As to etiology, cortical dysplasia was identified in seven patients. Epilepsy surgery should be considered for intractable childhood epilepsy based on individual clinical characteristics, including seizure status, cognitive development, and evidence indicating location of the seizure focus, rather than age.