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Biomedical subjects

A Leviton

Publications and source records attributed to A Leviton.

At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

Definitive classes of childhood supratentorial neuroglial tumors. The Childhood Brain Tumor Consortium.

Our objective in this study was to identify histologically homogenous classes of childhood supratentorial neuroglial tumors. Previously, we identified five quantitative histologic factors (differing linear combinations of 17 reliably recognized histologic features in neuroglial tumors). They account for much of the histologic variance in the 703 supratentorial tumors in the Childhood Brain Tumor Consortium (CBTC) database. In this study, we used the scores on the factors in cluster analyses and identified eight classes of neuroglial tumors. Each of these classes had significant differences in histology, allowing the separation of many of the conventional types of neuroglial tumors into two or more classes. For instance, fibrillary astrocytoma, pilocytic astrocytoma, subependymal giant cell astrocytoma, anaplastic astrocytoma, oligodendroglioma, and ependymoma were represented in two or more classes. Often these classes had statistically significant differences in survival distributions. For instance, the two classes of "anaplastic astrocytomas" have widely discrepant 5-year survival probabilities of 0.7 and 0.2. Use of the classes identified in this study ensures relatively homogeneous histologic subsets of tumors. We suggest that these classes will be useful for the selection of children for therapeutic clinical trials.

Astrocytoma↗
PubMedDate not supplied

Very low birthweight placenta: clustering of morphologic characteristics.

Our objective was to use factor analysis as a data reduction tool to organize a large number of placental pathologic features into useful aggregates. We examined 1146 placentas of live-born infants with a birth weight of 500-1500 g. We then conducted analyses of pairs of characteristics and multiple characteristics to identify "associated groups" and "factors," respectively. We found an associated group and factor that had placental features associated with acute inflammation and another associated group and factor that had features associated with vasculopathy. Acute umbilical vasculitis had the strongest correlation with other features of the acute inflammation associated group and factor. Gross evidence of acute inflammation (opacification and green appearance of membrane) was eliminated in the reduction from associated group to factor. Infarcts and syncytial knots were strongly dissociated with features of acute inflammation. The multiple pathologic features of the very low birthweight placenta can be aggregated into two associated groups or two factors. Lack of membrane opacification cannot be used as a criterion for declining microscopic examination. The absence of infarcts and syncytial knots should prompt a search for features of acute inflammation. If a placenta has two or more findings from the acute inflammation factor or the vasculopathy factor, it is unlikely to demonstrate features from the other factor.

Acute Disease↗
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Perinatal asphyxia.

Explore the source record for details and available documents.

Asphyxia Neonatorum↗
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Etiologic heterogeneity of intracranial hemorrhages in preterm newborns.

Hemorrhages in brain parenchyma and ventricles in preterm infants tend to be grouped as one entity. To help determine whether these hemorrhages should be viewed as one or more entities, we compared the risk profiles of 3 groups of hemorrhages defined by location and time of occurrence: early germinal matrix hemorrhage (GMH), late GMH, and late peri/intraventricular hemorrhage excluding GMH. These 3 groups were determined to have sufficient differences in various risk factors to warrant separate epidemiologic study.

Anesthesia, Spinal↗
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Problems with definitions and classifications of newborn encephalopathy.

Encephalopathy in the newborn has been classified in a manner suggesting that the etiology is known, such as hypoxic-ischemic and post-asphyxial encephalopathy. In the absence of evidence that most cases of newborn encephalopathy reflect these phenomena, we prefer the simple, descriptive terms, neonatal or newborn encephalopathy. Qualitative and quantitative grading schemes are described in this review and some of their potentially correctable limitations are discussed. The ideal grading scheme continues to be an unattained goal.

Asphyxia Neonatorum↗
PubMedDate not supplied

Low-level lead exposure, social class, and infant development.

A prospective cohort study was conducted to assess the association between early development and low-level prenatal and postnatal lead exposure. Infants' performance between 6 and 24 months on the Mental Development Index of the Bayley Scales of Infant Development declined with increasing concentration of lead in blood, but the decline varied with children's age at exposure, level of exposure, and socioeconomic status. Within the second year of life, the performance of children in lower socioeconomic strata was adversely affected at lower levels of prenatal exposure (blood lead levels of 6 to 7 micrograms/dl) than was the performance of children in higher socioeconomic strata. However, even the performance of these advantaged infants was lower when cord blood lead level exceeded 10 micrograms/dl, well below the figure currently regarded as the maximum permissable level for young children. Exploratory analyses suggested that early postnatal blood lead levels between 10 and 25 micrograms/dl were also associated with lower Mental Development Index scores, but only among children in lower socioeconomic strata.

Aging↗
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Sonographically detected subarachnoid hemorrhage: an independent predictor of neonatal posthemorrhagic hydrocephalus?

Blood from an intraventricular hemorrhage (IVH) can collect in the basilar cisterns and cause ventriculomegaly and eventual need for ventriculoperitoneal (VP) shunt. We looked for sonographic evidence of subarachnoid hemorrhage (SAH) in three basal cisterns and in the Sylvian fissure of 82 infants with IVH, 30 of whom had ventriculomegaly. We found that ultrasonographically diagnosed SAH and measurement of ventricular blood volume predict ventriculomegaly and need for VP shunt.

Cerebral Ventricles↗
PubMedDate not supplied

Variability of blood lead concentrations during infancy.

As part of a study of early childhood development, more than 200 children had their blood lead concentrations (PbB) determined semiannually during the first 2 yr of life. These children were selected from 11,837 consecutive births surveyed for umbilical cord PbB at Boston Lying-In Hospital. Candidate subjects were drawn from the highest, lowest, and middle deciles of PbB. The mean PbB was 7.2 +/- 5.3 (standard deviation) micrograms/dl at birth and did not change appreciably with age. However, the average change in an individual's PbB every 6 months was 4 micrograms/dl, which was several fold in excess of the analytical reproducibility. Only 25% of the children in the highest category at birth were in the highest category at 2 yr of age. Approximately 40% of the children remained in their immediately previous PbB tertile category. A stochastic description of these patterns of change fits the data. Our results should caution investigators who might wish to rely on a single determination to categorize children with PbB.

Fetal Blood↗
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Lead in milk and infant blood: a dose-response model.

As part of a longitudinal study of the sources and developmental effects of current urban lead exposure, lead was measured in tap water from the homes of 249 infants, in 100 breast milk samples, and in 73 samples of the infant formula used by non-nursing mothers. Also, the blood lead levels of the infants who received these fluids were determined at birth and at 6 months of age. Among the infants who were breast fed, the lead content of their milks correlated very well with their 6-month blood lead levels (r = .42, P = .0003). The mean lead content of infant formulas and breast milk were not significantly different, nor was the blood lead of children fed one or the other. Lead levels in maternal milk correlated poorly with umbilical cord blood lead (r = .18, P = .10). Tap water and infant blood lead levels correlated minimally (r = .11, P = .10). Since milk represents much of the diet of young infants and because breast milk lead levels are stable, it is possible to relate blood lead and daily dosage in this population.

Female↗
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Perinatal factors and seizure disorders: an epidemiologic review.

In this review, we assess the following six aspects of the epidemiological literature addressing the association between perinatal factors and seizure disorders (mainly of the grand mal type): (1) study design; (2) selection of cases; (3) selection of controls; (4) definition and ascertainment method of seizures; (5) definition and ascertainment method of perinatal factors; (6) sample size and power. Needed are studies of perinatal factors in a homogeneous group of seizure patients, such as those with grand mal seizures. Because of the rarity of the seizure disorder, most follow-up studies of this subject suffer from inadequate sample size. Improvements are suggested for case-control studies, which appear, by necessity, to be the more appropriate design.

Epidemiologic Methods↗
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Interobserver variability in the ILAE classification of seizures in childhood.

Observer variability in interpreting medical tests and in making diagnoses influences both clinical practice and research. Uniform classification of epileptic seizures is especially difficult. Although the ILAE classification scheme for seizures has been available for many years, the reliability of this system has not been previously assessed. Verbatim descriptions of seizure manifestations were transcribed from medical records as part of a large, population-based prevalence study of childhood epilepsy conducted in two countries in central Oklahoma. One senior neurologist and three neurology residents reviewed these descriptions independently and classified them by seizure type based on the ILAE system. Unweighted and weighted kappa statistics were used to assess the level of agreement between the study neurologist and each resident. The overall agreement between observer pairs in classifying seizure types based on all available descriptions was relatively poor (kappa = 0.24-0.38). Some improvement was evident when unclassified seizures were excluded, and comparisons were restricted to those based on descriptions with some degree of detail (kappa = 0.34-0.51). When specific types of seizures were classified, agreement was fair to excellent for most types (kappa = 0.45-0.90), with the exceptions of atypical absence (kappa = 0.11-0.28), partial seizures with secondary generalization (kappa = 0.26-0.40), and generalized motor seizures (kappa = 0.29-0.32). Sources of observer variability in addition to the classification scheme are considered. Use of specific criteria for the categorization of symptoms might improve the reliability of seizure classification.

Adolescent↗
PubMedDate not supplied

Prevalence of the epilepsies in children and adolescents.

The prevalence of epilepsy in children and adolescents from birth through age 19 years was determined for residents of two counties in central Oklahoma. Cases, identified from hospitals, clinics, private physicians' offices, and EEG laboratory and emergency room records, numbered 1,159, yielding a prevalence rate of 4.71 per 1,000. The prevalence was highest in children aged 1-4 years. Overall, males had a slightly higher prevalence rate than females (M:F = 1.1). However, the male/female ratio varied by age, with the group aged less than 1 year having the highest ratio (M:F = 1.5), and by type of epilepsy, with males having higher rates of simple partial epilepsy (M:F = 1.8) and infantile spasms (M:F = 1.5). The prevalence of epilepsy was higher in blacks than in whites. Differences in prevalence by race were confined primarily to generalized epilepsies (B:W = 1.8). The most common types of epilepsy were tonic, clonic, and tonic-clonic (1.14 per 1,000), complex partial (0.39 per 1,000), and partial seizures secondarily generalized (0.33 per 1,000). Approximately 70% of cases were considered idiopathic. Among the presumed causes were perinatal factors (7%), trauma (4%), central nervous system (CNS) infection (3%), and congenital/developmental factors (3). Sixty-five percent of cases had at least one additional medical problem. The most common types of comorbidity were motor handicap (13%) and developmental delay (24%).

Adolescent↗
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Antecedents and correlates of hypoplastic enamel defects of primary incisors.

Four hundred and fifty-five exfoliated primary incisors were obtained from children whose mothers provided information about a wide range of pre-, peri-, and postnatal characteristics of both the mother and child. These teeth then were examined for the presence of hypoplastic enamel defects (HED). The basic form of the null hypothesis tested was that children who had HED of a primary incisor did not differ from those who did not have such a defect. Of the primary incisors examined, 18.5% had HED (25.0% maxillary and 10.1% mandibular). The following items were found to be associated most strongly (P less than 0.003) with an increase in a child's risk of developing HED; 1) maternal antenatal history of smoking, higher prepregnancy weight, and failure to obtain prenatal care during the first trimester; 2) prematurity, low birth-weight and their associated correlates; and 3) postnatal measles infection. Left-handedness, maternal tea and Tylenol (McNeil Consumer Products Co., Fort Washington, PA) consumption, and failure to screen for undue lead burden were associated less prominently (P less than 0.05) with HED prevalence. Season of birth and serum and dentin lead levels were not related to the prevalence of HED. Many of these risk factors are also covariates of low socioeconomic status such as suboptimal nutrition and increased risk of infection. Additional investigation is needed to delineate the associations between specific pre- and perinatal nutritional and infectious factors, socioeconomic status, and HED development.

Child, Preschool↗
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Macroscopic enamel defects of primary anterior teeth--types, prevalence, and distribution.

A total of 40.7% of 509 exfoliated primary anterior teeth from children who were healthy products of uneventful pregnancies exhibited at least one macroscopic enamel defect. Twenty percent of the teeth exhibited hypoplastic defects (HD), 12.4% exhibited white-cream opacities (WCO), and 9.8% exhibited yellow-brown opacities (YBO). Slightly more than a third (33.6%) of the teeth had defects we considered to be developmental enamel defects (DED). The occurrence of DED did not vary with gender, side of mouth, individual tooth types, or racial background. DED occurred with increased frequency on maxillary teeth, facial surfaces, and the middle third of affected surfaces. These locations have thicker enamel than other sites and may be more susceptible to insult if vulnerability is a function of metabolic demand of the rapidly secreting ameloblasts. Twenty-five per cent of the maxillary incisors and 10.1% of the mandibular incisors exhibited HD whose locations coincided with enamel forming at birth. A third (33.3%) of the canines exhibited HD, which occurred most commonly in the middle third of the facial surfaces. These defects are believed to occur approximately six months postnatally and may be primarily due to mechanical trauma. YBO most commonly occurred on the middle third of the facial surfaces, while WCO on the gingival third. Neither YBO nor WCO followed a chronologic pattern.

Child↗
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Low-level lead exposure and infant development in the first year.

The developmental impact of prenatal and early postnatal low-level lead exposure was assessed in a prospective study of 249 middle and upper-middle class infants with umbilical cord blood lead levels in the range currently considered "normal." Infants were classified into three exposure groups: "low" (less than 3 micrograms/dl), "mid" (6 to 7 micrograms/dl), and "high" (greater than or equal to 10 micrograms/dl). At 6 and 12 months, the lead concentration of capillary blood was measured, and the Bayley Scales of Infant Development administered. At both ages, Mental Development Index scores, adjusted for confounding, were inversely related to infants' umbilical cord blood lead levels. The difference between the mean adjusted scores of the infants in the low and high cord blood lead groups was 5.8 points at 6 months and 7.3 points at 12 months. At neither age were scores significantly related to postnatal blood lead levels. Prenatal exposure to lead levels relatively common among urban populations appear to be associated with less favorable development through the first year of life.

Age Factors↗
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Early sensory-motor development and prenatal exposure to lead.

As part of a longitudinal study of the early developmental effects of exposure to lead, we administered the Bayley Scales of Infant Development at age 6 months to infants classified into three groups based on their umbilical cord blood lead levels ("low": mean = 1.8 micrograms/dl; "mid": mean = 6.5 micrograms/dl; "high": mean = 14.6 micrograms/dl). No infant had a cord blood lead level greater than 30 micrograms/dl, the level currently regarded as the upper limit of "normal" for young children. Multiple regression analyses indicated that high cord blood levels were associated with lower covariance-adjusted scores on the Mental Development Index. Scores on the Psychomotor Development Index were not significantly related to cord blood lead level. The level of lead in blood at 6 months of age was not associated with scores on either the Mental or Psychomotor Development Index. These data are compatible with the hypothesis that low levels of lead delivered transplacentally are toxic to infants.

Child Development↗