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PubMed2002

Neuroimaging characteristics of pseudosubcortical laminar heterotopia.

Subcortical laminar heterotopia (SLH) is a subtype of malformation of cortical development characterized by laminar gray matter between the cortex and ventricles, which can vary in thickness and may be continuous or discontinuous. The objective of this study is to describe a normal finding of high-resolution magnetic resonance imaging that may simulate an SLH. SLH is isointense to cortex on both T1- and T2-weighted/FLAIR images, usually both anteriorly and posteriorly in location. Conversely, pseudo-SLH is a normal variant present only at the posterior aspect of the brain, and with dark signal on both T1- and T2-weighted/FLAIR images.

Brain Diseases↗
PubMed1999

Surgical treatment of epilepsy--clinical, radiological and histopathological findings in 139 children and adults.

The present study relates clinical and radiological data to histopathological diagnoses in the first 139 patients (children and adults) in the Göteborg Epilepsy Surgery series. Temporal lobe resections were most common (54.0%) followed by frontal lobe (18.0%) and multilobar resections (11.5%). All histopathological specimens were re-evaluated in connection with this study. Parenchymal malformations and atrophic-gliotic lesions were the most common histopathological findings. Microdysgenesis was more common than major malformations (24.5% versus 11.5%). When the MRI scans were blindly re-evaluated the MRI findings correlated with histopathological diagnosis in all of the vascular malformations, in 77.8% of the tumours, in 76.5% of the cases with hippocampal sclerosis but only in 28.6% of the major cortical development malformations. Hemispherectomies carried the best seizure outcome prognosis followed by temporal lobe resections (75.0% versus 57.3% seizure free 2 years after surgery). Vascular malformations carried the best, and microdysgenesis the worst prognosis (76.9% versus 39.4% seizure free).

Adolescent↗
PubMed2005

Parenchymal lesions in pharmacoresistant temporal lobe epilepsy: dual and multiple pathology.

OBJECTIVES: Dual pathology is reported in 5-30% of temporal lobe resections performed in pharmacoresistant epilepsy. Dual pathology may be of importance for surgical planning and also for the understanding of the pathogenesis of epilepsy. We describe the frequency of dual or multiple pathology, i.e. more than one histopathological diagnosis, in adults with temporal lobe resections. MATERIAL AND METHODS: Surgical specimens from 33 consecutive patients with resections including mesial as well as neocortical temporal structures were reviewed. All histopathological findings were recorded. Post-mortem specimens from 11 control subjects were also reviewed. RESULTS: Dual or multiple pathology was found in almost half of the epilepsy patients (48%). Hippocampal sclerosis was found in 25 patients (76%), malformations of cortical development in 15 (46%), of which 12 (36%) were microdysgenesis, and low-grade tumours in seven (21%). Apart from mild gliosis, there were no histopathological changes in the control specimens. CONCLUSION: Dual or multiple pathology was a common finding in this group of adults with temporal lobe resections. In order to increase our understanding of how aetiological factors may combine in the development of seizures, we consider it relevant and important to report all histopathological findings in epilepsy surgery series.

Adult↗
PubMed2006

Focal cortical dysplasia: prevalence, clinical presentation and epilepsy in children and adults.

Focal cortical dysplasias (FCD) are defined as circumscribed malformations of cortical development. They result from an impairment of neuronal proliferation, migration and differentiation. In the diagnosis of focal epilepsy FCD prevalence ranges between 5% and 25%, depending on patient collective and imaging techniques. Several 'cryptogenic' epilepsies may be caused by FCD but have not been diagnosed because of the lack of high-quality magnetic resonance imaging assessment. Retrospective analysis of patients who have undergone epilepsy surgery can be biased because of the fact that they represent a mere subset of potential FCD diagnoses. Epilepsy typically manifests within the first years of life, but has been documented up to the age of 60 years. Cognitive impairment commonly accompanies early onset. Epilepsy is often refractory to antiepileptic drug (AED) treatment. Clinical observations and pathophysiological findings illustrate intrinsic epileptogenicity. Upregulation of drug transporter proteins has been found in FCD tissue. There is no specific drug treatment in FCD, as any AED used in focal epilepsy could prove effective. A sequential AED therapy should be designed individually and take side effects as well as developmental progresses into consideration. Fifty to sixty-five percent of FCD patients are rendered seizure-free after surgery. Presurgical evaluation should be initiated after two unsuccessful AED trials. Both risks and potential benefits regarding seizure control and developmental impairment need to be considered on an individual basis when deciding between surgical intervention and conservative treatment. Current knowledge on epilepsy course and psychomotor development in FCD is limited in the absence of qualified long-term studies combining imaging with cognitive evaluation.

Adult↗
PubMed2006

Ultraviolet radiation-B-induced cataract in albino rats: maximum tolerable dose and ascorbate consumption.

PURPOSE: To investigate the maximum tolerable dose (MTD) for cataract induced by ultraviolet radiation-B (UVB) in 7-week-old albino rats and to study the effect of UVB eye exposure on lens ascorbate content. METHODS: Fifty 7-week-old albino Sprague Dawley rats were unilaterally exposed in vivo to 300-nm UVB under anaesthesia, receiving 0, 0.25, 3.5, 4.3 and 4.9 kJ/m(2). The MTD was estimated based on lens forward light scattering measurements. Lens ascorbate content was determined in the processed lens using high performance liquid chromatography with UVR detection. RESULTS: Animals exposed to UVB doses >or=3.5 kJ/m(2) developed cortical cataracts. The MTD for avoidance of UVB-induced cataract was estimated to 3.01 kJ/m(2). UVB exposure decreased lens ascorbate concentration in the exposed lens in line with UVB dose, H(e), according to the models: C = C(NonCo) + C(Co)e(-kH(e) ) for exposed lenses; C = C(NonCo) + C(Co) for non-exposed lenses, and C(d) = C(Co)(e(-kH(e) ) - 1). Parameters for consumable and non-consumable ascorbate were estimated to C(NonCo) = 0.04 and C(Co) = 0.11 micromol/g wet weight of lens. For lens ascorbate difference, tau = 1/k = 0.86 kJ/m(2). A total of 63% of UVB consumable ascorbate has been consumed after only tau = 0.86 kJ/m(2), while MTD(2.3 : 16) = 3.01 kJ/m(2), indicating that ascorbate decrease is in the order of 3.5 times more sensitive to detecting UVR damage in the lens than forward light scattering. CONCLUSIONS: The MTD for avoidance of UVB-induced cataract in the 7-week-old albino Sprague Dawley rat was estimated to be 3.01 kJ/m(2). In vivo UVB exposure of the rat eye decreases lens ascorbate content following an exponential decline, and suprathreshold doses cause greater effect than subthreshold doses.

Animals↗
PubMed1991

Molecular mechanisms of glial-guided neuronal migration.

The migration of young neurons from their site of origin in proliferative zones out into neuronal layers is a hallmark of cortical development. Neuroanatomic studies show that astroglial fibers provide the primary substrate for neuronal migration. In vitro studies on living cells provide evidence that migrating neurons express distinguishing cytologic features including the formation of a specialized junction at the site of neuron-glia contact and the extension of an active leading process in the direction of migration. Our in vitro functional assays point to a critical role for astrotactin in neuron-glia binding during the developmental periods of glial-guided cell migration and assembly in brain. Other receptor systems, including neural cell adhesion systems, cadherins, and integrins are expressed by granule cells but do not appear to contribute to neuron-glia binding or to glial-guided neuronal migration. A role for astrotactin in glial-guided migration and assembly is supported by our observation that astrotactin is expressed by neurons and not glial cells and by restricted spatiotemporal expression of astrotactin in vivo, wherein astrotactin is expressed by migrating neurons and by neurons during periods of assembly into neuronal layers in developing brain. Understanding the regulation of astrotactin expression and its role in migration will provide fundamental insights into the role of glial-guided migration in the histogenesis of the brain.

Animals↗
PubMed1999

Co-localization of TSC1 and TSC2 gene products in tubers of patients with tuberous sclerosis.

Two genes, mutations in which result in the phenotype of tuberous sclerosis (TSC), have recently been cloned. TSC2 on chromosome 16p13.3 encodes the protein tuberin, which appears to have growth regulating properties. TSC1 on chromosome 9q34 encodes hamartin which, as yet, has no specified cellular functions. Polyclonal antibodies were raised to synthetic peptides representing portions of tuberin and hamartin and used in immunoblots and immunohistochemical studies to localize the proteins in surgically resected neocortical tubers from four TSC patients. On Western blots of autopsy brain specimens, K-562 cell, and NT2 lysates, each antibody labelled a single band at the expected molecular weight. In immunohistochemical protocols on paraffin embedded tissue, antibodies to both tuberin and hamartin prominently labelled atypical and dysmorphic neuroglial cells that are a defining feature of TSC tubers. Some abnormal cells within cortical tuber sections were labelled with both tuberin and hamartin antisera. Our results suggest that tuberin and hamartin are both robustly expressed in similar populations of neuroglial cells of TSC tubers, even in the presence of TSC1 or TSC2 germline mutations. The roles of these gene products in normal and abnormal cortical development, tuber pathogenesis and the generation of seizures remain to be defined.

Adolescent↗
PubMed1979

In vitro production of steroid cataract in bovine lens. Part II: measurement of sodium-potassium adenosine triphosphatase activity.

Fresh calf lesnses incubated in nutritive media containing dexamethasone phosphate or ouabain in concentrations ranging from 1 X 10(-4) M to 1 X 10(-8) M developed cortical opacification and showed significant inhibition of Na(+)-K(+) ATP'ase activity. Over a 3-day incubation period the decrease in Na+-K+ ATP'ase activity correlated well with the observed decrease in light transmission. The degree of enzyme inhibition and decrease in light transmission varied directly with the concentration of dexamethasone phosphate and ouabain, with significant changes observed at 'physiologic' and 'pharmacologic' concentrations of these agents. Lenses incubated for 4 days in dexamethasone phosphate or ouabain showed substantial increases in water content as well as an increase in Na+ and a decrease in K+ concentration. These data suggest that inhibition of the cation pump may play a significant role in the formation of steroid cataract in vitro.

Animals↗
PubMed2004

Foxg1 suppresses early cortical cell fate.

During mammalian cerebral corticogenesis, progenitor cells become progressively restricted in the types of neurons they can produce. The molecular mechanism that determines earlier versus later born neuron fate is unknown. We demonstrate here that the generation of the earliest born neurons, the Cajal-Retzius cells, is suppressed by the telencephalic transcription factor Foxg1. In Foxg1 null mutants, we observed an excess of Cajal-Retzius neuron production in the cortex. By conditionally inactivating Foxg1 in cortical progenitors that normally produce deep-layer cortical neurons, we demonstrate that Foxg1 is constitutively required to suppress Cajal-Retzius cell fate. Hence, the competence to generate the earliest born neurons during later cortical development is actively suppressed but not lost.

Animals↗
PubMed1973

Kitten visual cortex: short-term, stimulus-induced changes in connectivity.

Single neurons in the kitten visual cortex can be induced to increase their responsiveness to a repeated stimulus applied while the neurons are under observation. These short-term changes are in the same direction as the permanent modifications produced in whole populations of neurons following environmental manipulations during the "critical period" of cortical development, but are less pronounced and probably transient.

Age Factors↗
PubMed1977

Lens cataract formation and reversible alteration in crystallin synthesis in cultured lenses.

Embryonic chick lenses developed cortical cataracts and altered their pattern of delta-crystallin synthesis within 3 hours, if cultured without their vitreous body or traumatized with their vitreous body attached. delta-Crystallin reverted to the normal pattern by 24 hours in the cataractous lenses. Thus, biochemical differences that are only observable during the initial stages of cataractogenesis can exist between opaque and normal lenses.

Animals↗
PubMed2004

Ophthalmic impairment at 7 years of age in children born very preterm.

AIMS: To determine the prevalence of ophthalmic impairments in very preterm compared with term infants, the relation between impairments and cerebral ultrasound appearances and retinopathy, and the correlation with visual perception and motor and cognitive measures. SUBJECTS: 279 children at 7 years of age born before 32 weeks gestation within Liverpool during 1991-92 and attending mainstream schools, and 210 term controls. METHODS: Visual acuity was assessed by Snellen chart, and strabismus by the cover test. Stereopsis was determined using the TNO random dot test, and contrast sensitivity using the Cambridge low contrast gratings. Visual and motor abilities were assessed using the Developmental test of motor integration (VMI) and the Movement ABC. Intelligence was measured with the Wechsler intelligence scale for children UK. Perinatal cranial ultrasound and retinopathy data were extracted from clinical records. RESULTS: Children born preterm were significantly more likely to wear glasses, to have poor visual acuity, reduced stereopsis, and strabismus than term controls, but they showed no significant decrease in contrast sensitivity. Ophthalmic impairments were significantly related to poorer scores on the VMI, Movement ABC, and Wechsler IQ tests, but were not significantly related to neonatal cranial ultrasound appearances. Stage 3 retinopathy was related to poorer subsequent acuity. CONCLUSIONS: Children born very preterm and without major neurodevelopmental sequelae have an increased prevalence of ophthalmic impairments at primary school age which are associated with visual perceptional, motor, and cognitive defects. The cause may be a generalised abnormality of cortical development rather than perinatally acquired focal lesions of the brain.

Case-Control Studies↗
PubMed1997

Dominant X linked subcortical laminar heterotopia and lissencephaly syndrome (XSCLH/LIS): evidence for the occurrence of mutation in males and mapping of a potential locus in Xq22.

X linked subcortical laminar heterotopia and lissencephaly syndrome (XSCLH/ LIS) is an intriguing disorder of cortical development, which causes classical lissencephaly with severe mental retardation and epilepsy in hemizygous males, and subcortical laminar heterotopia (SCLH) associated with milder mental retardation and epilepsy in heterozygous females. Here we report an exclusion mapping study carried out in three unrelated previously described families in which males are affected with lissencephaly and females with SCLH, using 38 microsatellite markers evenly distributed on the X chromosome. Most of the X chromosome was excluded and potential intervals of assignment in Xq22.3-q23 or in Xq27 are reported. Although the number of informative meioses did not allow a decision between these two loci, it is worth noting that the former interval is compatible with the mapping of a breakpoint involved in a de novo X;autosomal balanced translocation 46,XX,t(X;2)(q22;p25) previously described in a female with classical lissencephaly. In addition, haplotype inheritance in two families showed a grandpaternal origin of the mutation and suggested in one family the presence of mosaicism in germline cells of normal transmitting males.

Adult↗
PubMed1998

Isolation of BAC clones spanning the Xq22.3 translocation breakpoint in a lissencephaly patient with a de novo X;2 translocation.

X linked lissencephaly and subcortical band heterotopia (XLIS/SBH) is a disorder of cortical development, which causes classical lissencephaly with severe mental retardation and epilepsy in hemizygous males and SBH associated with milder mental retardation and epilepsy in heterozygous females. Here we report the fine mapping of a breakpoint involved in a de novo X;autosomal balanced translocation (46,XX,t(X;2) (q22.3;p25.1)) previously described in a female with classical lissencephaly. We constructed a complete 490 kb BAC contig around the Xq22.3 breakpoint with 11 novel STSs and isolated three BAC clones spanning the breakpoint. This mapping information and BAC contig will be useful in the detailed characterisation of the XLIS gene and other contiguous genes which may also be involved in brain development or function.

Brain↗
PubMed2005

Vagus nerve stimulation: predictors of seizure freedom.

OBJECTIVES: To identify predictive factors for the seizure-free outcome of vagus nerve stimulation (VNS). METHODS: All 47 patients who had undergone VNS implantation at one centre and had at least one year of follow up were studied. They underwent complete presurgical evaluation including detailed clinical history, magnetic resonance imaging, and long term video-EEG with ictal and interictal recordings. After implantation, adjustment of stimulation parameters and concomitant antiepileptic drugs were at the discretion of the treating physician. RESULTS: Mean (SD) age of the patients was 22.7 (11.6) years (range 7 to 53). Six patients (13%) became seizure-free after the VNS implantation. Only two variables showed a significant association with the seizure-free outcome: absence of bilateral interictal epileptiform discharges (IED) and presence of malformation of cortical development (MCD). Epilepsy duration showed a non-significant trend towards a negative association with outcome. By logistic regression analysis, only absence of bilateral IED correlated independently with successful VNS treatment (p<0.01, odds ratio = 29.2 (95% confidence interval, 2.4 to 353)). Bilateral IED (independent or bilateral synchronous) was found in one of six seizure-free patients and in 33 of 41 non-seizure-free patients. When bilateral IED were absent, the sensitivity for seizure-free outcome was 0.83 (0.44 to 0.97), and the specificity was 0.80 (0.66 to 0.90). CONCLUSIONS: Bilateral IED was independently associated with the outcome of VNS. These results are preliminary because they were based on a small patient population. They may facilitate prospective VNS studies enrolling larger numbers of patients to confirm the results.

Adolescent↗
PubMed1975

Hemianopic colour blindness.

A man developed cortical blindness after cerebral infarction in the distribution of both posterior cerebral arteries. When he recovered from this condition, he was found to be colour blind in the left visual field, but not in the right. This unusual situation resulted in apparently contradictory performances on hemifield and free-field tasks of colour discrimination, naming, and recognition. The contradictions may be explained by interhemispheric competition between a hemisphere which could discriminate colours and a hemisphere which was colour blind.

Agnosia↗
PubMed1983

Unilateral occipital infarction: evaluation of the risks of developing bilateral loss of vision.

Fifty-eight patients with a unilateral infarction in the superficial area supplied by a posterior cerebral artery were followed (mean: 39.6 months). Thirteen (22.4%) developed cortical blindness associated with a delayed contralateral occipital infarction. Advanced age, general vascular risk, a history of strokes, Sylvian border-zone extension of the initial infarct, and an absence of improvement of initial visual field defects were strongly associated with spread to the other side. The lack of visual field improvement most accurately predicted a high risk of cortical blindness. A careful follow-up and controlled medical therapy is particularly indicated in these patients.

Adult↗
PubMed1999

Microdysgenesis in surgical specimens from patients with epilepsy: occurrence and clinical correlations.

Malformations of cortical development are commonly associated with epilepsy. In the first 139 consecutive patients in the Göteborg epilepsy surgery series, parenchymal malformations were found in 56. 1% of the children and in 23.1% of the adults. Microdysgenesis (MDG), which was the most common parenchymal malformation, was found in 35. 1% of the children and in 16.7% of the adults. The aim of this study was to identify clinical characteristics of patients with MDG. Mental retardation was found to be significantly more common in patients with major parenchymal malformations and in patients with MDG compared with patients without parenchymal malformations. Patients with major parenchymal malformations as well as patients with MDG also had a significantly earlier onset of seizures than patients without parenchymal malformations, also when adjusting for mental retardation. Patients with MDG were in these clinical aspects shown to closely resemble patients with major malformations. These findings suggest that MDG is a pathoanatomical entity of clinical relevance, with implications both in mental retardation and in epileptogenesis.

Adolescent↗