Diffuse cortical dysplasia, or the 'double cortex' syndrome: the clinical and epileptic spectrum in 10 patients

Frontal and central lobe focal dysplasia: clinical, EEG and imaging features

The authors studied 11 patients with developmental malformations and seizures originating from the frontal and central regions. Patients with centrally located seizures had primary involvement of the face or mouth; clonic activity involving the limb was also seen. Seizures among those with frontal lesions were primarily unilateral or bilateral tonic motor. Secondary generalized tonic-clonic seizures preceded by focal manifestations occurred infrequently in those with central localization, but were not rare in the frontal group. MRI revealed abnormalities in 10 patients, nine of whom underwent surgical resection with good results. Focal cortical dysplasia may be the underlying epileptogenic abnormality in young patients with clinical features suggestive of central or frontal cortical involvement.

Magnetic resonance imaging and epilepsy: neurosurgical decision making

Advances in magnetic resonance imaging (MRI) techniques have had an important impact on the decision-making process leading to surgical resection for chronic seizures. The MRI is now obtained relatively early in the work-up, and, when it shows abnormality, it assumes a crucial role in the detection of specific surgically remediable syndromes. These syndromes, when diagnosed by MR and other confirmatory studies such as electroencephalography (EEG), positron emission tomography (PET), magnetoencephalography (MEG), and neuropsychological testing, define the essential part of the surgical plan; that is, removal of the disease substrate. The availability of a host of MR techniques enable us to investigate epilepsy not only as a structural pathology but as physiological pathology reflected in abnormal blood flow, metabolism, and synaptic transmission. The mainstay of surgical treatment is the removal of the anatomic pathology, but other MR techniques may be helpful in the delineation of dual pathology in lesional cases, in appreciation of the full extent of microscopic pathology in developmental lesions, and in the imposition of restrictions on the resection based upon functional mapping. Finally, functional and anatomic maps obtained preoperatively can be related directly to the spatial coordinates of the exposed brain in the operating room using MRI-based frameless stereotactic methods. The final outcome, then, is the removal of the disease substrate without injury to adjacent, functionally salient cortical regions.

Posterior agyria-pachygyria with polymicrogyria: evidence for an inherited neuronal migration disorder

We describe two brothers with mental retardation and refractory epilepsy. MRI revealed symmetrical agyria-pachygyria of the temporo-occipito-parietal regions, areas of deeply infolded polymicrogyric parietal cortex, and dilated occipital horns (colpocephaly). The stereotyped clinical, EEG, and MRI findings suggest that this may be a distinct inherited condition and imply that agyria-pachygyria with polymicrogyria is not always sporadic.

MRI in cerebral developmental malformations and epilepsy

Cerebral developmental malformations are increasingly recognized as a major cause of developmental delay and epilepsy. The incidence of these developmental malformations in patients with epilepsy is not known, but epilepsy surgery data suggest that this pathology is commonly seen in children who undergo epilepsy surgery for intractable epilepsy. These malformations can be diagnosed by a combination of clinical, neurophysiological, and imaging techniques. However, imaging techniques such as MRI have been able to provide in vivo recognition of many of these malformations and have contributed to the recognition of specific syndromes. These malformations can be classified on an anatomical basis either into diffuse, unilateral, or generalized. However, a combination of imaging data in conjunction with genetics and embryology may be more appropriate in the future. Further technical developments promise to increase the sensitivity of MRI in detecting these malformations and may help to delineate the possible biology of these disorders.

The relative contributions of MRI, SPECT, and PET imaging in epilepsy

Functional and structural neuroimaging techniques are increasingly indispensable in the evaluation of epileptic patients for localization of the epileptic area as well as for understanding pathophysiology, propagation, and neurochemical correlates of chronic epilepsy. Although interictal single photon emission computed tomography (SPECT) imaging of cerebral blood flow is only moderately sensitive, ictal SPECT markedly improves yield. Positron emission tomography (PET) imaging of interictal cerebral metabolism is more sensitive than measurement of blood flow in temporal lobe epilepsy. Furthermore, PET has greater spatial resolution and versatility in that multiple tracers can image various aspects of cerebral function. Interpretation of all types of functional imaging studies is difficult and requires knowledge of time of most recent seizure activity and structural correlates. Only magnetic resonance imaging (MRI) can image the structural changes associated with the underlying epileptic process, and quantitative evidence of hippocampal volume loss has been highly correlated with seizure onset in medial temporal structures. Improved resolution and interpretation have made quantitative MRI more sensitive in temporal lobe epilepsy, as judged by pathology. When judged by electroencephalography (EEG), ictal SPECT and interictal PET have the highest sensitivity and specificity for temporal lobe epilepsy; these neuroimaging techniques have lower sensitivity and higher specificity for extratemporal EEG abnormalities. Regardless of the presence of structural abnormalities, functional imaging by PET or SPECT provides complementary information. Ideally these techniques should be used and interpreted together to improve the localization and understanding of epileptic brain.

Operative strategies for patients with cortical dysplastic lesions and intractable epilepsy

Cortical dysplastic lesions (CDLs) are usually identified by magnetic resonance imaging (MRI). Clinical, electrographic and histologic findings suggest that focal CDLs (FCDLs) are highly epileptogenic, often involve the rolandic cortex, and can present variable degrees of histopathologic abnormalities. An ictal or "ictal-like" bursting pattern of electrographic activity was recorded over dysplastic cortex in 65% of our patients. Resective surgery can eliminate or significantly reduce seizure frequency in many medically intractable patients, depending on lesion location, degree, and extent of histopathologic abnormalities. Best results are achieved when complete or major excision of both the MRI-visible lesion and the cortical areas displaying ictal electrographic activity can be performed. This is more likely when the degree of histopathologic abnormality is mild to moderate or when the lesion is in a temporal lobe. More severe histopathologic abnormalities and central insular or multilobar lesions usually lead to less favorable results: either major excision of the visualized lesion is impractical or the lesion is microscopically more extensive than shown by MRI. Multilobar resection or hemispherectomy for patients with infantile spasms associated with CDLs and for patients with hemimegalencephaly are often associated with dramatic improvement in seizure control. Callosotomy can be performed in selected patients with diffuse CDLs who have intractable drop attacks.

Magnetic resonance imaging in developmental disorders of the cerebral cortex

Developmental disorders of the neocortex are commonly associated with epilepsy. The development of magnetic resonance imaging (MRI) has advanced our understanding of these disorders by permitting accurate recognition and clinical correlation during life. These disorders have multiple etiologies and are dependent on the time of injury to the developing nervous system. MRI has permitted the classification of these malformations in three major groups: generalized disorders, unilateral hemispheric, and focal disorders. Generalized disorders include lissencephaly, pachygyria, band heterotopia, and subependymal heterotopias. Hemimegalencephaly comprised the unilateral disorder. Focal lesions include focal cortical dysplasia, polymicrogyria, schizencephaly, and focal subcortical heterotopias. The information provided by MRI, in conjunction with the clinicoelectrographic features, is extremely important in the recognition of these syndromes and for the appropriate medical and surgical management of those patients with epilepsy.

Brain glucose utilization in band heterotopia: synaptic activity of "double cortex"

Regional brain glucose utilization was investigated with positron emission tomography and fluorodeoxyglucose in 2 patients with a seizure disorder associated with diffuse band heterotopia, a condition known as "double cortex." Although 1 patient was examined shortly after the onset of the first seizures, the other had a long history of intractable epilepsy before examination. Magnetic resonance imaging revealed a symmetric and generalized band of ectopic gray matter and an overlying normal-looking cortex, without focal abnormality. Metabolic studies yielded comparable results in both patients, with similar and even higher glucose uptake in the layer of gray matter heterotopia compared to the normal cortex. These data suggest the persistence of some synaptic activity in the heterotopic neurons, which seems unaffected by age or by the time-course of epilepsy.

The association of cortical dysplasia and anterior horn arthrogryposis: a case report

We describe a 21-year-old woman with neurogenic congenital contractures (arthrogryposis) of the lower limbs, normal intelligence, hyper-reflexia and partial epilepsy. MRI revealed bilateral opercular (perisylvian) cortical dysplasia with infolding of cerebral cortex, a focal neuroblast migrational disorder. This type of migrational disorder is known to have a prenatal onset after the 20th fetal week, whereas the anterior horn cell degeneration responsible of neurogenic arthrogryposis originates at 12-14 weeks of gestation. A prenatal viral infection along the neural axis during both these gestational periods or a genetic defect could be responsible for both lesions in this case.

Band heterotopia: correlation of outcome with magnetic resonance imaging parameters

The "band heterotopia" or "double cortex" is a brain anomaly that is presumed to result from a premature arrest of neuronal migration. Patients with this anomaly are reported to have a variable clinical course that has been, heretofore, unpredictable. The clinical records and magnetic resonance (MR) imaging studies of 27 patients with band heterotopia were retrospectively reviewed in an attempt to determine whether imaging findings are useful in predicting clinical outcome of affected patients. Statistical analyses revealed the following correlations: (1) severity of T2 prolongation in the brain with motor delay (p = 0.03); (2) degree of ventricular enlargement with the age of seizure onset (p = 0.04), and with development and intelligence (p = 0.04); (3) severity of pachygyria with the age of seizure onset (p = 0.01), seizure type (p = 0.03), and an abnormal neurologic examination (p = 0.002); (4) parietal involvement with delayed speech development (p = 0.05); (5) occipital involvement with age of seizure onset (p = 0.006); (6) age of seizure onset with development and intelligence (p = 0.03) and with an abnormal neurologic examination (p = 0.04); and (7) severity of the pachygyria and thickness of band with development of symptomatic generalized epilepsy (p = 0.002 and p = 0.02, respectively) and Lennox-Gastaut syndrome (p = 0.002 and p = 0.01, respectively).

Epileptic seizures, arthrogryposis, and migrational brain disorders: a syndrome?

INTRODUCTION

Arthrogryposis multiplex congenita (AMC) may be associated with multiple developmental defects. In some severely affected newborns with AMC, autopsy studies have suggested a common mechanism of malmigration at the spinal and cerebral levels. To our knowledge, a constellation of arthrogryposis, epileptic seizures, and brain migrational anomalies in adult patients has not previously been described in a clinical material.

MATERIAL AND METHODS

Six consecutive adult patients with arthrogryposis multiplex congenita and epileptic seizures form the basis of the present study. Five patients had joint contractures and reduced muscle volume restricted to the lower extremities, whereas one patient had predominantly upper extremity affection. They were studied with magnetic resonance imaging (MRI), EEG, EMG, a neuropsychological test battery, and chromosome analysis.

RESULTS

Four of them had clear evidence of migrational brain disorders, demonstrated by MRI, in three of them roughly corresponding to the focal epileptiform EEG activity. Five of the patients had partial seizures, whereas one only had generalized tonic-clonic seizures. The MRI findings included polymicrogyria, pachygyria, and fused schizencephaly. Four had neurogenic EMG changes, one had myopathic EMG features, and one had an unremarkable EMG pattern in affected muscles. All patients with demonstrable migrational disorders showed abnormal neuropsychological features. Three patients were mentally retarded. A chromosome abnormality in the form of a ring chromosome 18 was present in one patient.

CONCLUSION

We suggest that AMC, epileptic seizures, and migrational brain disorders may form the integral parts of a hitherto undescribed syndrome in adults. A wide-spread defect in neuronal migration along the entire neural axis may be the underlying mechanism of the cerebral and the peripheral symptoms.

Subependymal heterotopia: a distinct neuronal migration disorder associated with epilepsy

Subependymal heterotopia has recently been recognised as a cause of epilepsy, but the clinical and investigational features have not been fully described. The clinical, psychometric, imaging, and electroencephalographic features of 13 adult patients with subependymal heterotopia and epilepsy have been reviewed. Age at seizure onset ranged from 18 months to 20 years (median 13 years). There were significantly more female (12) than male (1) patients (p < 0.01). Diagnosis of subependymal heterotopia was made by MRI in 11 patients and CT in two. The heterotopic grey matter was nodular in 11 patients and diffuse in two; bilateral in eight and unilateral in five. There were significantly more patients with predominant right than left cerebral hemisphere involvement (p < 0.01). The most commonly involved site was the occipital horn of the lateral ventricles (10 of 13 patients). Eleven patients presented with partial epilepsy, 10 of whom also had secondarily generalised seizures. The clinical description of the seizures often suggested either an occipital (four patients) or temporal (five patients) onset. Two patients presented with absence attacks without clear focal features. Patients demonstrated normal early milestones (12 of 13 patients), including normal motor development (all patients) and average or above average intelligence (10 of 13 patients). An EEG examination showed normal background activity in all but two patients, one of whom had large intracranial haematomas. Epileptiform activity was usually widespread (10 of 13 patients) and in three patients, there was generalised 3-Hz spike and wave activity that had previously led to an erroneous diagnosis of concomitant primary generalised epilepsy. Onset of epilepsy in the second decade of life, normal developmental milestones and intelligence, and the finding of an overwhelming female preponderance differentiates subependymal heterotopia from other cortical dysgeneses. The female preponderance supports the importance of the X chromosome and sex steroids in the maturation and development of the cerebral cortex.

Prenatal events and genetic factors in epileptic patients with neuronal migration disorders

Because disorders of neuronal migration to cerebral cortex in humans are believed to occur in the first half of gestation, prenatal events or genetic factors are suspected to have a pathogenetic role. We evaluated this by comparing the frequency of potentially harmful prenatal events and of genetic factors in a series of 40 patients (38 with epilepsy) with neuronal migration disorders (NMD) and in 40 epileptic controls, using a predetermined standardized questionnaire to minimize interviewer bias. Potentially harmful prenatal events (significant maternal physical trauma, ingestion of medications, exposure to roentgenograms, infections, uterine or metabolic abnormalities) were reported in the pregnancy histories of 58% of patients with NMD but in only 15% of epileptic controls (p = 0.0002). In contrast, peri- and postnatal potentially relevant etiologic factors were reported in the histories of only 22% of patients with NMD but in 50% of the epileptic controls (p = 0.01). Genetic factors (a family history of epilepsy, mental retardation, or congenital malformations of the CNS) were noted in 13 and 20% of the families, respectively. Stillbirths occurred only in the group with NMD, accounting for 3.06% of sibling pregnancies. The findings suggest that prenatal potentially harmful environmental events play a central role in the pathogenesis of NMD in humans.

X-linked pachygyria and agenesis of the corpus callosum: evidence for an X chromosome lissencephaly locus

A family of 5 affected male infants in 2 generations with an X-linked pattern of inheritance is described. All affected infants manifested intractable seizures, severe psychomotor retardation, growth failure, microphallus, and death during infancy. Three of the affected patients had radiological studies that demonstrated findings consistent with pachygyria-agyria and agenesis of the corpus callosum. We believe that this family represents a form of X-linked pachygyria-agyria (lissencephaly) that has not been described previously and suggests a locus for lissencephaly on the X chromosome.

Subcortical laminar heterotopia and lissencephaly in two families: a single X linked dominant gene

Neuronal migration disorders can now be recognised by MRI. This paper reports two families in which the mothers had subcortical laminar heterotopia and four of their children had either similar heterotopia (two girls) or severe pachygyria or lissencephaly (two boys). Laminar heterotopia was more evident on MRI T2 weighted images. The patients had mild to severe epilepsy and mental retardation depending on the extent of cortical abnormalities. In these families, subcortical laminar heterotopia, pachygyria, and lissencephaly seem to share the same X linked or autosomal dominant gene. No chromosomal abnormalities, especially of chromosome 17, could be identified. For appropriate genetic counselling of the family of a child with lissencephaly or subcortical laminar heterotopia, MRI should be performed in parents or siblings with mental retardation or epilepsy.

The place of neuronal migration abnormalities in child neurology

With the development of modern imaging techniques, disturbances of neuronal migration appear to be a major cause of epilepsy, mental retardation and chronic neurological disability in childhood. Sixty-nine cases are presented, including 46 of diffuse migration abnormalities and 23 of localized dysplasia. Patients with diffuse migration disorders presented with mental retardation, gross motor impairment and severe seizure disorders whereas in those with focal anomalies, epilepsy was the chief complaint. Magnetic resonance imaging, although usually diagnostic of migration disorders often does not allow definition of the pathologic type. Some EEG patterns, such as high amplitude fast rhythms or the theta-delta pattern are highly suggestive. Most cases of abnormal migration are sporadic and probably acquired. Some are due to chromosomal anomalies, especially of chromosome 17p where a gene for lissencephaly has been mapped. Familial cases occur with both recessive and possibly dominant inheritance. Epilepsy due to migration abnormalities is often intractable. Resection of dysplastic cortex may be effective for localized disease and callosotomy has been proposed for diffuse anomalies.

Interictal EEG findings in two cases with 'double cortex' syndrome

'Double cortex' is a neuroblast migrational disorder characterized by a diffuse band of heterotopic grey matter between the lateral ventricles and cerebral cortex which may be normal or macrogyric. The authors report two girls with 'double cortex' syndrome presenting intractable partial epilepsy and severe mental retardation. EEG data are analysed in detail because such patients presented a particular interictal EEG background activity, not only with very stable features during the different stages of vigilance, but also uninfluenced by seizure frequency or duration. The authors raise the possibility that a further in vivo diagnostic parameter for this syndrome has been identified.

Neuronal migration disorders: positron emission tomography correlations

We analyzed the interictal [18F]fluoro-2-deoxy-D-glucose positron emission tomography (PET) findings of 17 epileptic patients with neuronal migration disorders (NMDs). Fifteen patients had abnormal PET findings, i.e., focal hypometabolism in 9 patients and displaced metabolic activity of normal gray matter in 6. All 15 patients had magnetic resonance imaging (MRI) abnormalities; however, PET abnormality assisted in the identification of NMDs on MRI in 3 patients. Two patients with negative MRI also had negative PET studies. PET hypometabolism appeared to correlate with severity of neuronal dysgenesis or temporal lobe involvement, or both. Displaced metabolic activity of gray matter is regarded as a unique interictal [18F]fluoro-2-deoxy-D-glucose-PET finding in NMD. This study demonstrates variable metabolic patterns in NMD and that PET may be a useful complement to MRI in the evaluation of NMD.

Double cortex syndrome: electroclinical study of three cases

We describe three female patients (aged 10, 11 and 21 years) with a Magnetic Resonance appearance of band heterotopia, a diffuse neuronal migration disorder, also known as double cortex syndrome. The clinical picture was characterized by the association of epilepsy and mental retardation in all three cases, as has been previously described in patients with double cortex syndrome. The epileptic syndrome (Lennox-Gastaut syndrome in one case, and symptomatic partial epilepsy in the other two), the response to medical treatment, and the severity of mental retardation were markedly different in the three patients. No clear-cut relationship was found between the clinical picture and the severity of the neuronal migration disorder, as revealed by magnetic resonance imaging. In the three cases, EEG shares some common features: multifocal epileptic activity with frequent bilateral diffusion, and high-amplitude anterior fast activity, intermingled in two patients with bursts of repetitive spikes.

Ictal single-photon emission computed tomography demonstrates localized epileptogenesis in cortical dysplasia

We investigated the use of ictal single-photon emission computed tomography (SPECT) in 2 children with intractable epilepsy. Ictal scalp electroencephalographic studies failed to localize the epileptic focus and interictal data demonstrated widespread lateralized abnormalities. Ictal SPECT studies with technetium 99m-hexamethylpropyleneamineoxime demonstrated focal areas of hyperperfusion in the frontal lobes. Resection of the abnormal areas shown by SPECT was carried out despite evidence of large areas of epileptogenesis demonstrated by scalp and subdural electroencephalographic studies. Pathological material revealed cortical dysplasia. Ictal SPECT provides functional evidence for localized epileptogenesis in focal cortical dysplasia.

Hereditary nodular heterotopia accompanied by mega cisterna magna

This is the first report of hereditary nodular heterotopia accompanied by mega cisterna magna. Magnetic resonance imaging documented multiple bilateral subependymal nodules, which were isointense to gray matter. This disease entity is considered a dominant trait, since the mother and two daughters, half-sisters, were affected.

Magnetic resonance imaging and positron emission tomography of band heterotopia

A case of band heterotopia was reported with findings of positron emission tomography (PET). The patient was an 8-year-old girl who had mild mental retardation and intractable partial epilepsy. Her MRI showed another diffuse layer of gray matter underlying the normal-looking cortex and separated from it by an apparently normal layer of white matter. PET scan with [18F]fluorodeoxyglucose revealed that band heterotopia had the same degree of glucose metabolism as that of the overlying cortex.

Familial periventricular nodular heterotopia

We describe herein a 13-year-old girl, her 34-year-old mother and her 60-year-old grandmother who have periventricular heterotopic nodules. The mother has suffered from epileptic seizures since she was 15 years old, but the daughter and grandmother have had no epilepsy. They showed multiple uncalcified nodules on the lateral ventricular walls on CT. On MRI the intensity of the nodules was the same as that of the cerebral gray matter, suggesting heterotopia, and no other cerebral abnormalities were observed. Despite extensive examinations, neither have exhibited evidence of tuberous sclerosis. The periventricular nodular heterotopia observed in this family are a unique form of migration disorders, which may be caused by a dominant mutation.

Neuronal migrational disorders: diffuse cortical dysplasia or the "double cortex" syndrome

We report a 10-year-old girl who presented with a single episode of partial complex seizure. Neurological examination and psychological evaluation were normal. Electroencephalogram showed abnormalities in the left temporo-occipital region. Magnetic resonance imaging revealed a bilateral layer of tissue iso-intense with gray matter, between the wall of the lateral ventricle and the cortex, extending from the frontal to the occipital region, and enlarged left lateral ventricle. The images indicated diffuse cortical dysplasia, also known as band heterotopia or "double cortex", and left cortical hemiatrophy.

Stages and patterns of centrifugal arrest of diffuse neuronal migration disorders

Centrifugal migration of newly generated neuroblasts toward the cortical surface can be arrested at different levels, resulting in anatomically different disorders. This is illustrated by three patients with diffuse or generalized neuronal migration disorders (NMDs): pachygyria, subcortical laminar heterotopia ('double-cortex' syndrome), and periventricular laminar heterotopia. All had medically intractable partial and generalized epileptic seizures, but there was no close correlation between the type of dysplasia and intelligence or clinical pattern. The low intelligence found in these patients may relate to the epileptic syndrome, rather than to the NMDs alone. MRI suggested that in this spectrum of disorders the migration process was arrested at different stages, depending on the extent, timing and site of damage to radial glial fibres.

Surgical treatment of children with medically intractable frontal or temporal lobe epilepsy: results and highlights of 40 years' experience

Etiologic, pathologic, and clinical features of possible prognostic significance were studied in 118 children who underwent frontal or temporal lobe epilepsy surgery at the Montreal Neurological Institute (MNI) between 1940 and 1980 (excluding tumor cases). Mean age of seizure onset was 5.1 years (range 0-12 years), mean age at operation was 11.7 years (range 0.6-15 years), and median duration of follow-up was 15 years (range 2-31 years). Thirteen of 45 frontal surgery patients and 43 of 73 temporal surgery patients had an excellent outcome. In the frontal surgery group, this was restricted almost entirely to patients with an established etiology, particularly if this included a circumscribed resectable structural abnormality. In the temporal surgery group, a history of early, prolonged febrile seizures was usually associated with good outcome, unless there was additional evidence of extratemporal epilepsy. In the entire series, the presence of a nonresectable structural lesion or secondarily generalized seizures was associated with a poor outcome.

The 'double cortex' syndrome on MRI

We report a 6-year-old girl with diffuse subcortical heterotopia (band heterotopia), an unusual type of ectopic gray matter on magnetic resonance imaging (MRI). Her cerebral parenchyma had four layers consisting of cortex, thin outer white matter, diffuse subcortical heterotopia, and inner white matter around the lateral ventricles, giving the appearance of a 'double cortex'. The overlying cortex had midly broad gyri, especially in the frontal lobes. MRI showed the appearance of laminar heterotopia, a classical pathological entity. The double cortex syndrome is presumably a radiological delineation of laminar heterotopia. Her development was slightly delayed and she was clumsy and easily upset, with poor impulse control. However, her daily life was largely unaffected in spite of the severe abnormalities on MRI. She had abnormal movements during sleep, and sleeping EEG showed high voltage spindles in the bilateral frontal areas but no epileptic discharges. It could not be determined whether or not these movements were epileptic. The double cortex syndrome, an anomaly of the central nervous system associated with mental retardation, epilepsy, behavioral problems, and exclusive occurrence in girls, will be established as a clinico-radiological entity.

Neuronal migration disorders: a contribution of modern neuroimaging to the etiologic diagnosis of epilepsy

Computed tomography and magnetic resonance imaging enable the identification of neuronal migration disorders during life. Several specific syndromes have been identified and early diagnosis of previously unrecognized entities is now possible. We report 51 patients with imaging. Thirty-two had a single widespread cortical dysplastic lesion. Twenty-eight had focal corticectomies. From a pathological standpoint, these encompassed focal cortical dysplasia (14 cases) and forme fruste of tuberous sclerosis (10 cases). These two groups of patients were indistinguishable from the clinical and radiological standpoint. In only two was the MRI examination normal. In addition, there were 10 with bilateral perisylvian dysplasia, four with diffuse cortical dysplasia or the "double cortex" syndrome, three with hemimegalencephaly, one with megalencephaly, and one with nodular neuronal heterotopia. The electroclinical and imaging findings led to the development of specific surgical strategies for the alleviation of the intractable seizures in each of these radiologically-defined syndromes.