Clinical features and long term outcome of epilepsy in periventricular nodular heterotopia. Simple compared with plus forms

OBJECTIVES: Little is known about the long term outcome of patients with periventricular nodular heterotopia (PNH) and epilepsy, particularly the course of seizures. This study investigated the electroclinical and prognostic features of 16 patients with PNH. METHODS: Of 120 patients with epilepsy and malformations of cortical development, 16 had PNH. Of these, eight patients had periventricular nodules only (simple PNH) and eight also presented with other cortical or cerebral malformations (subcortical heterotopia; polymicrogyria; focal dysplasia; schizencephaly; cortical infolding; agenesis of the corpus callosum; mega cisterna magna and cerebellar atrophy) (PNH plus). All patients underwent clinical, neurophysiological, and MRI investigation. The mean follow up was 17.3 years (2-40 years). RESULTS: Two electroclinical patterns emerged: (1) The first pattern, associated with simple PNH, was characterised by normal intelligence and seizures, usually partial, which began during the second decade of life. The seizures never became frequent and tended to disappear or become very rare. The EEG showed focal abnormalities. (2) The second pattern, associated with PNH plus, was characterised by mental retardation and seizures that began during the first decade of life. The seizures were very frequent in most cases and sudden drops were observed in six patients. Seizures were medically refractory in four patients. The EEG showed focal and bisynchronous abnormalities. CONCLUSIONS: Two groups of PNH patients with different electroclinical and neuroradiological features can be identified after a long term follow up. The presence of other types of cortical or cerebral malformations, in addition to periventricular nodules, determines a poor prognosis.     

Unlayered polymicrogyria and agenesis of the corpus callosum: a relevant association?

Summary Three anatomical cases of unlayered polymicrogyria associated with agenesis of the corpus callosum and heterotopias are presented. The cortical dysplasia includes: (1) thin unlayered cortical mantle with radial disposition but no horizontal organisation of the neurons; (2) microgyria with fused molecular layers; and (3) persisting transitory cells in the molecular layer (Cajal-Retzius cells, subpial granular layer). A Golgi study of the cortex in one case shows abnormal orientation of the neuronal dendritic tree in the superficial area along the fused molecular layers. Heterotopias are of two types: scattered neurons in the subcortical region and in layer I; and nodular heterotopias in the paraventricular region and in centrum semi ovale. This type of cortical dysplasia differs from the classical four-layered microgyria and is similar to the cortical anomalies described in Aicardi syndrome. One case presented here has Aicardi syndrome, while the two others, one girl and one boy, do not meet the criteria for Aicardi syndrome; in particular, they do not display chorioretinal lacunae. Nevertheless, this neuropathological association is responsible for severe mental retardation and epilepsy, and incites the search for a genetic origin like that in Aicardi syndrome.     

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.     

Microcephaly associated with abnormal gyral pattern

Primary microcephaly is a heterogeneous group of cerebral malformations either with a relatively well-preserved or an abnormal gyral pattern. We describe the MRI findings and clinical features of 14 children with the combination of microcephaly and an abnormal gyral pattern. All children except one were Arabs and nine out of the 14 patients were born to consanguineous parents. Seven patients showed features of a simplified gyral pattern with relatively preserved posterior fossa structures. Two boys had a cortical malformation in the agyria-pachygyria spectrum; one of these two patients showed agenesis of the corpus callosum and severe cerebellar hypoplasia as well. The microcephaly was associated with polymicrogyria and leukoencephalopathy in two patients, with cortical dysplasia and hypogenesis of the corpus callosum in one patient, with agyria-pachygyria with callosal and pontocerebellar dysplasia in one patient, and a simplified gyral pattern with severe cerebellar hypoplasia in one case. One patient died in the neonatal period and three in infancy. All patients, who survived the neonatal period, had developmental delay, intellectual disability, and neurological deficits, and nine suffered from epilepsy.     

Oculocerebrocutaneous (Delleman) syndrome: report of two cases

We describe two cases of oculocerebrocutaneous syndrome (OCCS) or Delleman syndrome, characterized by congenital anomalies that involve the skin, orbit, and central nervous system (CNS). Complete MRI studies of the orbit, CNS and the entire spinal region must be performed in these cases. New MRI techniques can show cortical malformations, such as polymicrogyria, lissencephaly, or abnormal disposition of cortical sulci and gyri. Lesions can be bilateral or unilateral, as occurred in our patients. In one case, the ocular, skin, cerebral, and cerebellar lesions involved mainly the same side, whereas in the second case, all anomalies were generalized and the patient also showed skin hypopigmented lesions distributed bilaterally. Both patients show severe encephalopathy and Dandy-Walker malformation. One case is blind and shows generalized hydrocephalus, and the other one has vision through an eye, and has complete agenesis of the corpus callosum and severe disorder of neuronal migration and cortical organization with polymicrogyria and abnormal cortical sulci and gyri in a cerebral hemisphere. Our second case shows arachnoid cysts in both temporal, retrocerebellar, and spinal (D(8)-D(11)) regions, and lipoma in the pontomedullary and spinal (D(4)-D(7)) regions. The latter features correspond more to ECCL than to OCCS. The overlap between the two syndromes is unquestionable and it is possible that they constitute different manifestations of the same disorder.     

Magnetic resonance imaging and histological studies of corpus callosal and hippocampal abnormalities linked to doublecortin deficiency

Mutated doublecortin (DCX) gives rise to severe abnormalities in human cortical development. Adult Dcx knockout mice show no major neocortical defects but do have a disorganized hippocampus. We report here the developmental basis of these hippocampal abnormalities. A heterotopic band of neurons was identified starting at E17.5 in the CA3 region and progressing throughout the CA1 region by E18.5. At neonatal stages, the CA1 heterotopic band was reduced, but the CA3 band remained unchanged, continuing into adulthood. Thus, in mouse, migration of CA3 neurons is arrested during development, whereas CA1 cell migration is retarded. On the Sv129Pas background, magnetic resonance imaging (MRI) also suggested abnormal dorsal hippocampal morphology, displaced laterally and sometimes rostrally and associated with medial brain structure abnormalities. MRI and cryosectioning showed agenesis of the corpus callosum in Dcx knockout mice on this background and an intermediate, partial agenesis in heterozygote mice. Wild-type littermates showed no callosal abnormalities. Hippocampal and corpus callosal abnormalities were also characterized in DCX-mutated human patients. Severe hippocampal hypoplasia was identified along with variable corpus callosal defects ranging from total agenesis to an abnormally thick or thin callosum. Our data in the mouse, identifying roles for Dcx in hippocampal and corpus callosal development, might suggest intrinsic roles for human DCX in the development of these structures.     

Selective reduction of Von Economo neuron number in agenesis of the corpus callosum

Von Economo neurons (VENs) are large spindle-shaped neurons localized to anterior cingulate cortex (ACC) and fronto-insular cortex (FI). VENs appear late in development in humans, are a recent phylogenetic specialization, and are selectively destroyed in frontotemporal dementia, a disease which profoundly disrupts social functioning and self-awareness. Agenesis of the corpus callosum (AgCC) is a congenital disorder that can have significant effects on social and emotional behaviors, including alexithymia, difficulty intuiting the emotional states of others, and deficits in self- and social-awareness that can impair humor, comprehension of non-literal or affective language, and social judgment. To test the hypothesis that VEN number is selectively reduced in AgCC, we used stereology to obtain unbiased estimates of total neuron number and VEN number in postmortem brain specimens of four normal adult controls, two adults with isolated callosal dysgenesis, and one adult whose corpus callosum and ACC were severely atrophied due to a non-fatal cerebral arterial infarction. The partial agenesis case had approximately half as many VENs as did the four normal controls, both in ACC and FI. In the complete agenesis case the VENs were almost entirely absent. The percentage of neurons in FI that are VENs was reduced in callosal agenesis, but was actually slightly above normal in the stroke patient. These results indicate that the VEN population is selectively reduced in AgCC, but that the VENs do not depend on having an intact corpus callosum. We conclude that in agenesis of the corpus callosum the reduction in the number of VENs is not the direct result of the failure of this structure to develop, but may instead be another consequence of the genetic disruption that caused the agenesis. The reduction of the VEN population could help to explain some of the social and emotional deficits that are seen in this disorder.     

MR imaging in congenital disorders of the brain

MR imaging is an excellent tool for use in diagnosing congenital malformations of the brain. Such malformations cannot be reliably recognized or classified without an insight into the basic processes of the fetal development of the brain. Cortical malformations are classically divided into (1) malformations of neuronal proliferation, i.e. of stem cell proliferation in the periventricular germinal matrix zone, (2) disorders of neuronal migration, i.e. of the radial migration of the neurons from the periventricular germinal matrix zone to the cortical surface, and (3) disorders of cortical organization. Other cerebral malformations are agenesis or dysgenesis of the corpus callosum, encephaloceles, and various kinds of holoprosencephaly. Chiari malformation ans disorders on the Dandy-Walker spectrum are relatively common, primarily infratentorial disorders. Rarer infratentorial disorders are Joubert syndrome, rhombencephalosynapsis and Lhermitte Duclos syndrome.     

Epileptogenic brain malformations: radiological and clinical presentation and indications for genetic testing

Malformations of cortical development (MCD) represent a major cause of developmental disabilities and severe epilepsy. Advances in imaging and genetics have improved the diagnosis and classification of these conditions. Up to now, eight genes have been involved in different types of MCD. Lissencephaly-pachygyria and subcortical band heterotopia (SBH) represent a malformative spectrum resulting from mutations of either LIS1 or DCX genes. LIS1 mutations cause a more severe malformation in the posterior brain regions. DCX mutations usually cause anteriorly predominant lissencephaly in males and SBH in female patients. Additional forms are X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia associated with mutations of the ARX gene. Lissencephaly with cerebellar hypoplasia (LCH) encompass heterogeneous disorders named LCH type a to d. LCHa are related with mutation in LIS1 or DCX, LCHb with mutation of RELN gene, and LCHd could be related with TUBA1A gene. Polymicrogyria encompass a wide range of clinical, aetiological and histological findings. Among several syndromes, recessive bilateral fronto-parietal polymicrogyria has been associated with mutations of the GPR56 gene. Bilateral perisylvian polymicrogyria showed a linkage to chromosome Xq28 in some pedigrees, and mutations in SRPX2 gene in others conditions. X-linked bilateral periventricular nodular heterotopia (BPNH) consists of BPNH with focal epilepsy in females and prenatal lethality in males. Filamin A (FLNA) mutations have been reported in some families and in sporadic patients. It is possible to infer the most likely causative gene by brain imaging studies and other clinical findings. Based on this experience, a detailed phenotype analysis is needed to develop the most efficient research on MCD in the future.     

Expression of erythropoietin and its receptor in the brain of late-gestation fetal sheep, and responses to asphyxia caused by umbilical cord occlusion

Asphyxia and hypoxia are common threats faced by the fetus in utero. In late-gestation fetal sheep, asphyxia produced by umbilical cord occlusion (UCO) results in widespread lipid peroxidation and apoptosis. Adaptive mechanisms that might limit fetal brain damage include induction of the hemopoietic cytokine, erythropoietin (EPO). In unanesthetized fetal sheep, we investigated if 1 or 2 bouts of brief asphyxia (UCO for 10 min) induced EPO and EPO type I receptor (EPO-R) expressions, with the second UCO repeated 48 h after the first. Fetal brains were recovered 48 h after either sham, 1 x or 2 x UCO at 129-133 (term approximately 147) days of gestation and prepared for immunocytochemistry. In age-matched control brain, low levels of EPO and EPO-R proteins were present in oligodendrocytes (OLs), periventricular and cortical white matter (WM), with no EPO and very low EPO-R expression in neurons. After 1 x UCO, EPO and EPO-R expressions were increased in astrocytes (periventricular and cortical WM, striatum, corpus callosum), choroid plexus epithelial cells, scattered neurons in cortical layers IV-VI, hippocampal CA1 neurons, and in the molecular and granule layers of the cerebellum. After 2 x UCO, higher levels of EPO and EPO-R occurred in the periventricular and cortical WM, corpus callosum, hippocampal CA1, and in neurons of all cortical layers. Paradoxically, EPO and EPO-R were now lower in hippocampal CA1 neurons and cerebellar molecular and granule cell layers. Few OLs expressed EPO or EPO-R after 1 x or 2 x UCO. Thus, brief asphyxia induces EPO and EPO-R in fetal astrocytes, but only after repeated asphyxial insult in neurons. Whether this is a response to increased injury, or represents an adaptive response that limits further cell death and brain damage awaits further investigation.     

The value of somesthetic homolateral evoked potentials in agenesis of the corpus callosum (author's transl)

The authors describe the homolateral somesthetic evoked responses in 8 cases of agenesis of the corpus callosum. They stress the differences compared to normals in the same way that contralateral somesthetic evoked responses differ. The authors consider the possibility of an independent cortical generator responsible for this response and suggest that systematic recording of somesthetic homolateral evoked potentials might be of considerable value in early diagnosis of agenesis of the corpus callosum.     

Spectrum of corpus callosum agenesis

Magnetic resonance imaging and clinical features of 16 children with agenesis of the corpus callosum are reviewed. The patients were classified in three groups. Eight children had agenesis of the corpus callosum without substantial involvement of other brain areas. This group included patients with interhemispheric cyst, lipoma, or partial agenesis (hypogenesis) of the corpus callosum. Four patients in the second group manifested severe telencephalic dysgenesis in addition to agenesis of the corpus callosum. In the third group, agenesis of the corpus callosum was a component of a syndrome in four children. The outcome was not favorable for the majority of patients, even in the first group without significant involvement of other systems. Severe handicaps with developmental delay, intellectual disability, and neurologic deficit were observed in patients with additional telencephalic dysgenesis or syndromic form of corpus callosum agenesis.     

Magnetic resonance imaging in agenesis of the corpus callosum

The recent use of computed tomography (CT) scan is providing an easy diagnoses of agenesis of corpus callosum which had been difficult to diagnose only by clinical signs and symptoms. Since, more neuropsychological studies on agenesis of corpus callosum are being done, clinical details of agenesis of corpus callosum are being clarified. We examined magnetic resonance imaging (MRI) on 3 patients who were suspected to have agenesis of corpus callosum by CT scan. And we studied the usefulness of MRI in agenesis of corpus callosum. Case 1. We studied a thirty-two-year-old right-handed man with a one-year history of amyotrophic lateral sclerosis. He had no callosal disconnection syndrome. CT scan on horizontal view showed dilated third ventricle, the dilatation of the occipital horns and wide separation of the lateral ventricles. On coronal view, CT scan showed the absence of the corpus callosum, the concave mesial borders of the lateral ventricle, the dilatation of the third ventricle and its abnormal dorsal extent(bat-wing appearance). On sagittal MRI (the inversion recovery technique), the corpus callosum was absent and the convolutions and sulci were arranged radically centering the third ventricle (radial distribution). But the anterior commissure was preserved. Case 2. We studied a fourty-one-year-old right-handed man with a seven-year history of hyper ventilation syndrome. He had no callosal disconnection syndrome. CT scan showed the similar findings as those of case 1. On sagittal MRI (the inversion recovery technique), the corpus callosum was absent, and the convolutions and sulci showed radial distribution. But the anterior commissure was preserved.(ABSTRACT TRUNCATED AT 250 WORDS)     

A novel mutation in the β-tubulin gene TUBB2B associated with complex malformation of cortical development and deficits in axonal guidance

Neurological disorders characterized by abnormal neuronal migration, organization, axon guidance, and maintenance have recently been associated with missense and splice-site mutations in the genes encoding α- and β-tubulin isotypes TUBA1A, TUBB2B, TUBB3, and TUBA8. We found a novel heterozygous mutation c.419G > C in exon 4 of the gene encoding TUBB2B in a female with microcephaly, agenesis of the corpus callosum, open-lip schizencephaly of the left parietal lobe, extensive polymicrogyria, basal ganglia and thalami dysmorphisms, and vermis and right third nerve hypoplasia. The missense change results in a glycine to alanine substitution; the mutated residue falls within an invariant glycine-rich region and therefore is likely to result in impaired protein function and possibly microtubule formation. This study expands the spectrum of brain malformations associated with mutations in the β-tubulin gene TUBB2B, supporting its critical role in migration/organization and axon guidance processes. In addition, it suggests a possible genetic aetiology of schizencephaly, thus strengthening the hypothesis that there is a common pathophysiological base in polymicrogyria and schizencephaly.     

Impairment of binocular vision in the adult cat induces plastic changes in the callosal cortical map

In the primary visual cortex of normally reared adult cat, neurons activated through the corpus callosum are almost entirely located at the 17/18 border. They display small receptive fields distributed along the central vertical meridian of the visual field and are orientation selective. Here we demonstrate that a few weeks of monocular deprivation or unilateral convergent strabismus produced in adulthood does not modify the cortical distribution of these neurons, but leads to an increase of their receptive field size mainly toward the ipsilateral hemifield and to a loss of their orientation selectivity. We conclude that manipulation of binocular vision in the adult modifies neither the location of the primary callosal cortical map nor its retinotopy. In contrast, it induces functional plastic changes in this map which lead to a significant widening of the area of visual space signalled through the corpus callosum. These plastic changes are interpreted as the result of the strengthening of normally hidden subthreshold synaptic inputs.     

Pattern of childhood epilepsies with neuronal migrational disorders in Oman

Neuronal migrational disorders form a significant cause of psychomotor delay and intractable epilepsy in children. Pediatric neurology services are available at Sultan Qaboos University Hospital, Muscat, Oman, which is a tertiary care hospital for the whole country. The children undergoing evaluation for developmental delay and epilepsy formed the subjects of the study. Data were analyzed from children found to have neuronal migrational disorders on imaging (computed tomography [CT] or magnetic resonance imaging [MRI]). There were 40 cases of neuronal migrational disorders. Corpus callosum agenesis and lissencephaly or pachygyria formed the major group. There were 22 cases of corpus callosum agenesis, 12 of lissencephaly or pachygyria, 2 of schizencephaly, and 1 each of polymicrogyria, holoprosencephaly, hydranecephaly, and hemimegalencephaly. Nineteen of these 40 (47.5%) cases of neuronal migrational disorders had epilepsy. The break-down was 8 of 22 cases of corpus callosum agenesis (36%), 7 of 12 (58.3%) cases of lissencephaly or pachygyria, and 1 each of polymicrogyria, hydranencephaly, and hemimegalencephaly. The family history of developmental delay, similar to the index case, was present in two children with lissencephaly. However, the brain imaging did not reveal the abnormality. The types of seizures were infantile spasms in five, tonic-clonic in nine, myoclonic in two, partial in one, and mixed in five. Nineteen of 40 cases of neuronal migrational disorders had epilepsy. Only 2 of 19 (10.5%) with epilepsy had good seizure control. This raises the possibility of more and more surgical intervention in the management of such cases. Neuronal migrational disorders are related to exogenous and genetic factors from the 6th to 26th weeks of gestation. Molecular and genetic research is defining the mechanism of these disorders. This could help in early diagnosis, prevention, and eventual gene therapy in such conditions.     

TUBA1A mutation-associated lissencephaly: case report and review of the literature

Lissencephaly is a disorder of neuronal migration resulting in abnormal cerebral cortical sulcation and gyration. Affected children present with microcephaly, developmental delay, and early-onset epileptic seizures. Recently, de novo missense mutations in the tubulin α-1A (TUBA1A) gene were identified as causing a distinctive radiologic phenotype comprising of posteriorly predominant lissencephaly with dysgenetic corpus callosum, cerebellar and brainstem hypoplasia, and more recently, polymicrogyria. We describe a 14-month-old girl with TUBA1A mutation-associated lissencephaly, and summarize the clinical and neuroradiologic findings of 19 cases in the literature.     

A rare case of Aicardi syndrome with severe brain malformation and hepatoblastoma

A 2-month-old Japanese girl exhibited tonic seizure, agenesis of the corpus callosum, lacunar chorioretinopathy, vertebral anomalies, electroencephalographic abnormalities and a malignant tumor. Autopsy revealed a hepatoblastoma and severe brain malformations consisting of callosal agenesis, arhinencephaly, marked polymicrogyria and optic nerve anomalies. It was thought that the pathogenic factor in this case may exert its effect during the fourth or fifth week of intrauterine life, and then may continue until the beginning of neuronal migration (about 3 months). This is the first reported case of Aicardi syndrome associated with hepatoblastoma, and may provide a link between teratogenicity and oncogenicity.