RESUMO
Electric conductors with dimensions reduced to the nanometer scale are the prerequisite of the quantum devices upon which the future advanced electronics is expected to be based. In the past, the fabrication of one-dimensional (1D) wires has been a particular challenge because they have to be defect-free over their whole length, which can be several tens µm. Excellent 1D wires have been produced by cleaving semiconductors (GaAs, AlGaAs) in ultra high vacuum and overgrowing the pristine edge surface by molecular beam epitaxy (MBE)1,2. Unfortunately, this cleaved edge overgrowth (CEO) technique did not find wide-spread use because it requires a series of elaborate steps that are difficult to accomplish. In this Letter, we present a greatly simplified variation of this technique where the cleaving takes place in ambient air and the MBE overgrowth is replaced by a standard deposition process. Wires produced by this cleaved edge deposition (CED) technique have properties that are as least as good as the traditional CEO ones. Due to its simplicity, the CED technique offers a generally accessible way to produce 1D devices.
RESUMO
Neural networks for processing language often are reorganized in patients with epilepsy. However, the extent and location of within and between hemisphere re-organization are not established. We studied 45 patients, all with a left hemisphere seizure focus (mean age 22.8, seizure onset 13.3), and 19 normal controls (mean age 24.8) with an fMRI word definition language paradigm to assess the location of language processing regions. Individual patient SPM maps were compared to the normal group in a voxel-wise comparison; a voxel was considered to be significant if its z-value exceeded mid R:2mid R:. Subsequently, we used principal component analysis with hierarchical clustering of variance patterns from individual difference maps to identify four patient sub-groups. One did not differ from normal controls; one had increased left temporal activation on the margin of regions activated in controls; two others had recruitment in right inferior frontal gyrus, middle frontal gyrus and temporal cortex. Right hemisphere activation in these two groups occurred in homologues of left hemisphere regions that sustained task activation. Our study used novel data driven methods to find evidence for constraints on inter-hemispheric reorganization of language in recruitment of right homologues, and, in a subpopulation of patients, evidence for intra-hemispheric reorganization of language limited to the margins of typical left temporal regional activation. These methods may be applied to investigate both normal and pathological variance in other developmental disorders and cognitive domains.
Assuntos
Epilepsia/fisiopatologia , Processamento de Imagem Assistida por Computador , Idioma , Rede Nervosa/fisiopatologia , Adolescente , Adulto , Mapeamento Encefálico , Estudos de Casos e Controles , Criança , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Plasticidade Neuronal , Testes Neuropsicológicos , Análise de Componente Principal , Adulto JovemRESUMO
Von Hippel-Lindau (VHL) disease is a rare autosomal dominant genetic disorder with retinal and nervous system haemangioblastomas, phaeochromocytomia, kidney, pancreas and endolymphatic tumors. The management of childbirth, including epidural anaesthesia is controversial. The possible presence of vascular malformations (retinal and central nervous system and spinal haemangioblastomas) increases the risk of disrupting central nervous system haemangioblastoma during delivery and when epidural anaesthesia is initiated. We report 3 cases of patient with VHL disease with successful epidural anaesthesia 2 for delivery and 1 for Caesarean section.
Assuntos
Anestesia Epidural , Anestesia Obstétrica , Doença de von Hippel-Lindau/complicações , Adulto , Cesárea , Feminino , Humanos , Recém-Nascido , Gravidez , Resultado da GravidezRESUMO
Single ventricle is a relatively rare abnormality found only in 0.5-1.5% of patients with congenital heart disease. Pregnancy results in an increased maternal morbidity and mortality in patients with right to left shunting, especially in cases associated with pulmonary hypertension and polycythemia and decreased arterial oxygen saturation. Most complications arise from decreases in systemic vascular resistance, causing an increase in right to left shunting and further hypoxemia and acidosis. For this reason, the major regional anaesthetic techniques are often avoided in these patients. The authors reported two successful management of regional anaesthesia for both caesarean and vaginal delivery.
Assuntos
Anestesia Obstétrica , Cardiopatias Congênitas/complicações , Adulto , Anestesia por Condução , Cesárea , Parto Obstétrico , Eletrocardiografia , Feminino , Ventrículos do Coração/anormalidades , Humanos , Monitorização Intraoperatória , GravidezRESUMO
BACKGROUND: Atypical language dominance is common in patients with temporal lobe epilepsy. We examined the association of left temporal hypometabolism with laterality of fMRI activation in a language task in a cross-sectional study. METHODS: Thirty patients with temporal lobe epilepsy (mean age 32.4 ± 11.0 years [range 18-55]; epilepsy onset 15.3 ± 11.3 years [range 0.8-40]; 22 left focus, 8 right focus) had (18)fluoro-deoxyglucose (FDG)-PET using noninvasive cardiac input function. After MRI-based partial volume correction, regional glucose metabolism (CMRglc) was measured and asymmetry index, AI = 2(l - R)/(L + R), calculated. fMRI language dominance was assessed with an auditory definition decision paradigm at 3 T. fMRI data were analyzed in SPM2 using regions of interest from Wake Forest PickAtlas (Wernicke area [WA], inferior frontal gyrus [IFG], middle frontal gyrus [MFG]) and bootstrap laterality index, LI = (l - R/L + R). RESULTS: Nineteen patients had ipsilateral temporal hypometabolism; 3 of 4 patients with atypical language had abnormal FDG-PET. Increasing left midtemporal hypometabolism correlated with decreased MFG LI (r = -0.41, p < 0.05) and showed trends with WA LI (r = -0.37, p = 0.055) and IFG LI (r = -0.31, p = 0.099); these relationships became more significant after controlling for age at onset. Increasing hypometabolism was associated with fewer activated voxels in WA ipsilateral to the focus and more activated voxels contralaterally, but overall, activation amount in left WA was similar to subjects without left temporal hypometabolism (t = -1.39, p > 0.10). CONCLUSIONS: We did not find evidence of impaired blood oxygenation level-dependent response in hypometabolic cortex. Regional hypometabolism appears to be a marker for the temporal lobe dysfunction that leads to displacement of language function.
Assuntos
Dominância Cerebral , Epilepsia do Lobo Temporal/psicologia , Fluordesoxiglucose F18/farmacocinética , Idioma , Imageamento por Ressonância Magnética , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos/farmacologia , Lobo Temporal/metabolismo , Adolescente , Estudos Transversais , Epilepsia do Lobo Temporal/diagnóstico , Epilepsia do Lobo Temporal/metabolismo , Epilepsia do Lobo Temporal/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Lobo Temporal/diagnóstico por imagem , Lobo Temporal/fisiopatologiaRESUMO
OBJECTIVE: To characterize children with new-onset seizures presenting as status epilepticus at a tertiary care children's hospital. METHODS: Prospectively collected data were reviewed from a database derived from a mandated critical care pathway. A total of 1,382 patients presented with new-onset seizures between 2001 and 2007. RESULTS: A total of 144 patients presented in status epilepticus. The average age was 3.4 years. The majority of seizures (72%) lasted between 21 and 60 minutes. The majority of patients had no significant past medical history; one-fourth had a family history of epilepsy. Five (4%) patients with EEGs had electrographic seizures during the study, captured only with prolonged monitoring. The most common etiology was febrile convulsion, followed by cryptogenic. The most common acute symptomatic cause was CNS infection; the most common remote symptomatic cause was cerebral dysgenesis. Combined CT and MRI provided a diagnosis in 30%. CT was helpful in identifying acute vascular lesions and acute edema, whereas MRI was superior in identifying subtle abnormalities and remote symptomatic etiologies such as dysplasia and mesial temporal sclerosis. CONCLUSIONS: Children who present in status epilepticus that is not a prolonged febrile convulsion should undergo neuroimaging in the initial evaluation. For any child who presents in status epilepticus and has not yet returned to baseline, the possibility of nonconvulsive status epilepticus should be considered. Although CT is often more widely accepted, especially in the urgent setting, strong consideration for MRI should be given when available, due to the superior yield.
Assuntos
Encéfalo/fisiopatologia , Convulsões Febris/diagnóstico , Estado Epiléptico/diagnóstico , Adolescente , Distribuição por Idade , Distribuição de Qui-Quadrado , Criança , Pré-Escolar , Eletroencefalografia , Feminino , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Estudos Prospectivos , Convulsões Febris/fisiopatologia , Estado Epiléptico/fisiopatologia , Fatores de TempoRESUMO
OBJECTIVE: To investigate the presenting characteristics of new-onset afebrile seizures in infants (age 1-24 months) and the yield of neuroimaging. METHODS: Prospective data were obtained from a standardized evaluation and management plan mandated by a critical care pathway. A total of 317 infants presented with new-onset afebrile seizures between 2001 and 2007. EEG was performed on 90.3%, head CT was obtained on 94%, and MRI was obtained on 57.4%. RESULTS: We found half of the infants had partial features to their seizures, yet evidence for primary generalized seizures was rare. The majority had more than 1 seizure upon presentation. Seizures in this age group tended to be brief, with 44% lasting less than 1 minute. EEG abnormalities were found in half. One-third of CTs were abnormal, with 9% of all CTs requiring acute medical management. Over half of MRIs were abnormal, with cerebral dysgenesis being the most common abnormality (p < 0.05). One-third of normal CTs had a subsequent abnormal MRI-only 1 resulted in altered medical management. CONCLUSIONS: Infantile seizures are usually brief, but commonly recurrent, and strong consideration should be made for inpatient observation. Acute imaging with CT can alter management in a small but important number of infants. Due to the superior yield, strong consideration for MRI should be given for all infants, as primary generalized seizures are rare, and there is a high rate of cerebral dysgenesis.
Assuntos
Envelhecimento/fisiologia , Encéfalo/patologia , Encéfalo/fisiopatologia , Diagnóstico por Imagem/métodos , Diagnóstico por Imagem/tendências , Convulsões/diagnóstico , Convulsões/fisiopatologia , Fatores Etários , Encéfalo/anormalidades , Mapeamento Encefálico , Córtex Cerebral/anormalidades , Córtex Cerebral/patologia , Córtex Cerebral/fisiopatologia , Pré-Escolar , Eletroencefalografia/métodos , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Lactente , Recém-Nascido , Masculino , Malformações do Sistema Nervoso/complicações , Malformações do Sistema Nervoso/diagnóstico , Malformações do Sistema Nervoso/fisiopatologia , Valor Preditivo dos Testes , Estudos Prospectivos , Processamento de Sinais Assistido por Computador , Tomografia Computadorizada por Raios X/métodosRESUMO
OBJECTIVE: To investigate interhemispheric and intrahemispheric reorganization in patients with localization-related epilepsy. METHOD: We studied 50 patients with a left hemispheric focus and 20 normal right-handed controls with a 3T echoplanar imaging blood oxygen level dependent functional MRI auditory-based word definition decision task. Data were analyzed using SPM 2. Using region of interest for Broca and Wernicke areas and an asymmetry index (AI), patients were categorized as left language (LL; AI > or = 0.20) or atypical language (AL; AI <0.20) for region. The point maxima activation for normal controls (p <0.05 corrected FDR) was identified in Broca and midtemporal regions and then used as a point of reference for individual point maxima identified at p < 0.001, uncorrected. RESULTS: Patient groups showed increased frequency of having activation in right homologues. Activation in AL groups occurred in homologous right regions; distances for point maxima activation in homologous regions were the same as point maxima distances in normal control activation in left regions. Distances for LL patient in left regions showed a trend for differences for midtemporal gyrus (6 mm posterior, 3 mm superior) but variability around mean difference distance was significant. There was no effect of age at epilepsy onset, duration, or pathology on activation maxima. CONCLUSIONS: Right hemisphere language regions in patients with left hemispheric focus are homologues of left hemisphere Broca and broadly defined Wernicke areas. We found little evidence for intrahemispheric reorganization in patients with left hemisphere epilepsy who remain left language dominant by these methods.
Assuntos
Epilepsia Parcial Complexa/fisiopatologia , Lobo Frontal/fisiopatologia , Lateralidade Funcional , Idioma , Lobo Temporal/fisiopatologia , Adolescente , Adulto , Idade de Início , Mapeamento Encefálico , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Testes de Linguagem , Imageamento por Ressonância Magnética , Masculino , Plasticidade Neuronal , Adulto JovemRESUMO
BACKGROUND: Autosomal dominant partial epilepsy with auditory features (ADPEAF) is an idiopathic focal epilepsy syndrome with auditory symptoms or receptive aphasia as major ictal manifestations, frequently associated with mutations in the leucine-rich, glioma inactivated 1 (LGI1) gene. Although affected subjects do not have structural abnormalities detected on routine MRI, a lateral temporal malformation was identified through high resolution MRI in one family. We attempted to replicate this finding and to assess auditory and language processing in ADPEAF using fMRI and magnetoencephalography (MEG). METHODS: We studied 17 subjects (10 affected mutation carriers, 3 unaffected carriers, 4 noncarriers) in 7 ADPEAF families, each of which had a different LGI1 mutation. Subjects underwent high-resolution structural MRI, fMRI with an auditory description decision task (ADDT) and a tone discrimination task, and MEG. A control group comprising 26 volunteers was also included. RESULTS: We found no evidence of structural abnormalities in any of the 17 subjects. On fMRI with ADDT, subjects with epilepsy had significantly less activation than controls. On MEG with auditory stimuli, peak 2 auditory evoked field latency was significantly delayed in affected individuals compared to controls. CONCLUSIONS: These findings do not support the previous report of a lateral temporal malformation in autosomal dominant partial epilepsy with auditory features (ADPEAF). However, our fMRI and magnetoencephalography data suggest that individuals with ADPEAF have functional impairment in language processing.
Assuntos
Córtex Auditivo/fisiopatologia , Percepção Auditiva/genética , Epilepsias Parciais/complicações , Transtornos da Linguagem/fisiopatologia , Percepção da Fala/genética , Estimulação Acústica , Adulto , Córtex Auditivo/patologia , Mapeamento Encefálico , Transtornos Cromossômicos/complicações , Transtornos Cromossômicos/genética , Epilepsias Parciais/genética , Feminino , Lateralidade Funcional/genética , Genes Dominantes/genética , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Transtornos da Linguagem/genética , Transtornos da Linguagem/patologia , Testes de Linguagem , Imageamento por Ressonância Magnética , Magnetoencefalografia , Masculino , Mutação/genética , Proteínas/genética , Tempo de Reação/genéticaRESUMO
OBJECTIVE: We investigated the relationship between partial epilepsy, MRI findings, and atypical language representation. METHODS: A total of 102 patients (4 to 55 years) with left hemisphere epileptogenic zones were evaluated using three fMRI language tasks obtained at 1.5 or 3T with EPI BOLD techniques: verbal fluency, reading comprehension, and auditory comprehension. fMRI maps were visually interpreted at a standard threshold and rated as left or atypical language. RESULTS: Atypical language dominance occurred in 30 patients (29%) and varied with MRI type (p < 0.01). Atypical language representation occurred in 36% (13/36) with normal MRI, 21% (6/29) with mesial temporal sclerosis, 14% (4/28) with focal cortical lesions (dysplasia, tumor, vascular malformation), and all (6/6) with a history of stroke. Multivariate logistic regression analysis found handedness, seizure onset, and MRI type accounted for much of the variance in language activation patterns (chi(2) = 24.09, p < 0.01). Atypical language was more prevalent in patients with early seizure onset (43.2%, p < 0.05) and atypical handedness (60%, p < 0.01). None of the three clinical factors were correlated with each other (p > 0.40). Patients with atypical language had lower verbal abilities (F = 6.96, p = 0.01) and a trend toward lower nonverbal abilities (F = 3.58, p = 0.06). There were no differences in rates of atypical language across time, age groups, or MRI scanner. CONCLUSION: Early seizure onset and atypical handedness, as well as the location and nature of pathologic substrate, are important factors in language reorganization.
Assuntos
Epilepsia Parcial Complexa , Transtornos da Linguagem , Comportamento Verbal/fisiologia , Adolescente , Adulto , Idade de Início , Criança , Pré-Escolar , Epilepsia Parcial Complexa/complicações , Epilepsia Parcial Complexa/fisiopatologia , Feminino , Lateralidade Funcional , Humanos , Lactente , Testes de Inteligência , Transtornos da Linguagem/etiologia , Transtornos da Linguagem/fisiopatologia , Testes de Linguagem , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Estudos Retrospectivos , SemânticaRESUMO
OBJECTIVE: To investigate the degree of language dominance in patients with left and right hemisphere seizure foci compared to normal volunteers using a fMRI reading comprehension task. METHODS: Fifty patients with complex partial epilepsy, aged 8 to 56 years and 33 normal volunteers, aged 7 to 34 had fMRI (1.5 T) and neuropsychological testing. Participants silently named an object described by a sentence compared to a visual control. Data were analyzed with region of interest (ROI) analysis based on t maps for inferior frontal gyrus (IFG), midfrontal gyrus (MFG), and Wernicke area (WA). Regional asymmetry indices (AIs) were calculated [(L - R)/(L + R)]; AI > 0.20 was deemed left dominant and AI < 0.20 as atypical language. RESULTS: Left hemisphere focus patients had a higher likelihood of atypical language than right hemisphere focus patients (21% vs 0%, chi2 < 0.002). Left hemisphere focus patients, excluding those with atypical language, had lower regional AI in IFG, MFG, and WA than controls. Right hemisphere focus patients were all left language dominant and had a lower AI than controls in WA and MFG, but not for IFG. AI in MFG and WA were similar between left hemisphere focus/left language patients and right hemisphere focus patients. Patients activated more voxels than healthy volunteers. Lower AIs were attributable to greater activation in right homologous regions. Less activation in the right-side WA correlated with better verbal memory performance in right focus/left hemisphere-dominant patients, whereas less strongly lateralized activation in IFG correlated better with Verbal IQ in left focus/left hemisphere-dominant patients. CONCLUSIONS: Patients had lower asymmetry indices than healthy controls, reflecting increased recruitment of homologous right hemisphere areas for language processing. Greater right hemisphere activation may reflect greater cognitive effort in patient populations, the effect of epilepsy, or its treatment. Regional activation patterns reflect adaptive efforts at recruiting more widespread language processing networks that are differentially affected based on hemisphere of seizure focus.