Elizabeth B. Isaacs

Hippocampal Volume and Everyday Memory in Children of Very Low Birth Weight

Children born preterm and of very low birth weight have an increased incidence of learning difficulties, but little is known about the specific nature of their cognitive deficits and the underlying neuropathology. We hypothesized that their vulnerability to hypoxic, metabolic, and nutritional insults would lead to reduced hippocampal volumes and to deficits in memory because of the role of the hippocampus in this domain of cognition. Neuropsychological and magnetic resonance imaging methods were used to investigate this hypothesis in adolescents born preterm (≤30 wk gestation, n = 11) or full-term (n = 8). The preterm group had significantly smaller hippocampal volumes bilaterally, despite equivalent head size, and showed specific deficits in certain aspects of everyday memory, both on objective testing and as indicated by parental questionnaires. The preterm group also had a specific deficit in numeracy. The reduced hippocampal volumes and deficits in everyday memory have previously been unrecognized, but their prevalence in a group of neurologically normal children is striking.

Outcome after ischaemic stroke in childhood.

A parental questionnaire was used to investigate the outcome for children who had had ischaemic stroke, who were seen at Great Ormond Street Hospital, London between 1990 and 1996. The results of functional assessments carried out by a physiotherapist and an occupational therapist, and of quantitative evaluations carried out by a neuropsychologist were used for validation where possible. The relationship between clinical and radiological factors and outcome were examined. The children were aged between 3 months and 15 years at the time of stroke (median age 5 years) and the period of follow‐up ranged from 3 months to 13 years (median duration 3 years). Of the 90 children for whom data were obtained, 13 (14%) had no residual impairments. Outcome was good in 37 children (40%) and poor in 53 (60%) (defined according to whether impairments interfered with daily life). Agreement, as measured by Cohens kappa, was good or very good between the parents’responses and the qualitative measures provided by the medical professionals and the therapists, but only fair to moderate for the quantitative measures provided by the neuropsychologists. This may reflect different parental perceptions of the physical and cognitive aspects of outcome. Younger age at time of the stroke was the only significant predictor of adverse outcome.

The effect of early human diet on caudate volumes and IQ.

Early nutrition in animals affects both behavior and brain structure. In humans, randomized trials show that early nutrition affects later cognition, notably in males. We hypothesized that early nutrition also influences brain structure, measurable using magnetic resonance imaging. Prior research suggested that the caudate nucleus may be especially vulnerable to early environment and that its size relates to IQ. To test the hypothesis that the caudate nucleus could be a neural substrate for cognitive effects of early nutrition, we compared two groups of adolescents, assigned a Standard- or High-nutrient diet in the postnatal weeks after preterm birth. Groups had similar birth status and neonatal course. Scans and IQ data were obtained from 76 adolescents and volumes of several subcortical structures were calculated. The High-nutrient group had significantly larger caudate volumes and higher Verbal IQ (VIQ). Caudate volumes correlated significantly with VIQ in the Standard-nutrient group only. Caudate volume was influenced by early nutrition and related selectively to VIQ in males, but not in females. Our findings may partly explain the effects of early diet on cognition and the predominant effects in males. They are among the first to show that human brain structure can be influenced by early nutrition.

A review of cognitive outcome after unilateral lesions sustained during childhood.

Views on human brain organization early in development have swung back and forth between the extreme notions of complete equipotentiality and adult-like specialization. Recent research on the cognitive effects of early brain damage supports an intermediate position and suggests that many claims on the older literature must be re-examined in the light of new evidence that cognitive impairments are sometimes attributable to previously ignored factors, such as a history of seizures, time since injury, and unsuspected lesions that are now detectable with neuroimaging techniques. (J Child Neurol 1994;9(Suppl):2S67-2S73).

The Development of Intellectual Abilities in Pediatric Temporal Lobe Epilepsy

Summary:  Purpose: The aim of this study was to examine the impact of clinical variables, particularly age at onset of epilepsy, on intellectual function in a group of children with temporal lobe epilepsy (TLE).

Developmental amnesia and its relationship to degree of hippocampal atrophy.

Two groups of adolescents, one born preterm and one with a diagnosis of developmental amnesia, were compared with age-matched normal controls on measures of hippocampal volume and memory function. Relative to control values, the preterm group values showed a mean bilateral reduction in hippocampal volume of 8–9% (ranging to 23%), whereas the developmental amnesic group values showed a reduction of 40% (ranging from 27% to 56%). Despite equivalent IQ and immediate memory scores in the two study groups, there were marked differences between them on a wide variety of verbal and visual delayed memory tasks. Consistent with their diagnosis, the developmental amnesic group was impaired relative to both other groups on nearly all delayed memory measures. The preterm group, by contrast, was significantly impaired relative to the controls on only a few memory measures, i.e., route following and prospective memory. We suggest that early hippocampal pathology leads to the disabling memory impairments associated with developmental amnesia when the volume of this structure is reduced below normal by ≈20–30% on each side. Whether this is a sufficient condition for the disorder or whether abnormality in other brain regions is also necessary remains to be determined.

Lateralization of brain function in childhood revealed by magnetic resonance spectroscopy

We used proton magnetic resonance spectroscopy (sup 1 H MRS) for the assessment of focal brain pathology in 22 right-handed children with a diagnosis of intractable temporal lobe epilepsy, and we related this pathology to cognitive dysfunction. Cognitive assessment was based on measurements of verbal IQ, performance IQ, and the Paired Associate Learning subtest of the Wechsler Memory Scale. Five of the 22 children showed no abnormalities of the temporal lobes on1 H MRS, seven showed unilateral pathology, and 10 showed bilateral abnormalities. We found that left-sided pathology is associated with a loss of verbal cognitive functions, whereas right-sided pathology is associated with a loss of nonverbal functions. These findings are consistent with the pattern of lateralization of brain function that has been observed in adults. NEUROLOGY 1996;46: 974-977.

Early Diet and General Cognitive Outcome at Adolescence in Children Born at or Below 30 Weeks Gestation

OBJECTIVE To test the hypothesis that effects of early diet on cognition observed at age 8 years persist in adolescents born preterm at < or = 30 weeks gestational age. STUDY DESIGN A subgroup from a preterm infant cohort recruited for a randomized trial studying the effects of early dietary intervention was assessed at age 16 years. IQ scores were compared between those assigned a high-nutrient diet (n = 49) or standard-nutrient diet (n = 46) in infancy at both 8 and 16 years. RESULTS At age 8 years, the high-nutrient group had higher mean Verbal IQ (VIQ; P = .03), Performance IQ (P = .01), and Full-Scale IQ (P = .02) scores compared with the standard-nutrient group; the VIQ difference persisted at adolescence (P = .02). This effect was accounted for principally by a significant difference in the mean Verbal Comprehension Index score (P < .008). CONCLUSIONS A brief period of dietary intervention after preterm birth, principally between 26 and 34 weeks of gestation, affected IQ at age 16 years. A standard-nutrient diet was associated with lower VIQ, accounted for mainly by differences in verbal comprehension, which persisted after control of social factors.

Aluminum Exposure From Parenteral Nutrition in Preterm Infants: Bone Health at 15-Year Follow-up

OBJECTIVE: Aluminum has known neurotoxicity and may impair short-term bone health. In a randomized trial, we showed reduced neurodevelopmental scores in preterm infants who were previously exposed to aluminum from parenteral nutrition solutions. Here, in the same cohort, we test the hypothesis that neonatal aluminum exposure also adversely affects long-term bone health, as indicated by reduced bone mass. METHODS: Bone area (BA) and bone mineral content (BMC) of lumbar spine, hip, and whole body were measured with dual radiograph absorptiometry in 13- to 15-year-olds who were born preterm and randomly assigned standard or aluminum-depleted parenteral nutrition solutions during the neonatal period. RESULTS: Fifty-nine children (32% of survivors) were followed. Those who were randomly assigned to standard parenteral nutrition solution had lower lumbar spine BMC, apparently explained by a concomitant decrease in bone size. In nonrandomized analyses, children who were exposed to neonatal aluminum intakes above the median (55 μg/kg) had lower hip BMC (by 7.6% [95% confidence interval 0.21–13.8]; P = 0.02), independent of bone (or body) size. CONCLUSIONS: Neonates who are exposed to parenteral aluminum may have reduced lumbar spine and hip bone mass during adolescence, potential risk factors for later osteoporosis and hip fracture. These findings need confirmation in larger, more detailed studies. Nevertheless, given our previous finding of adverse developmental outcome in these individuals and the sizeable number of contemporary infants who undergo intensive neonatal care and are still exposed to aluminum via parenteral feeding solutions, the potential adverse long-term consequences of early aluminum exposure now deserve renewed attention.

Nutrition and neurodevelopment in children: focus on NUTRIMENTHE project.

There is growing evidence that early nutrition affects later cognitive performance. The idea that the diet of mothers, infants, and children could affect later mental performance has major implications for public health practice and policy development and for our understanding of human biology as well as for food product development, economic progress, and future wealth creation. To date, however, much of the evidence is from animal, retrospective studies and short-term nutritional intervention studies in humans. The positive effect of micronutrients on health, especially of pregnant women eating well to maximise their child’s cognitive and behavioural outcomes, is commonly acknowledged. The current evidence of an association between gestational nutrition and brain development in healthy children is more credible for folate, n-3 fatty acids, and iron. Recent findings highlight the fact that single-nutrient supplementation is less adequate than supplementation with more complex formulae. However, the optimal content of micronutrient supplementation and whether there is a long-term impact on child’s neurodevelopment needs to be investigated further. Moreover, it is also evident that future studies should take into account genetic heterogeneity when evaluating nutritional effects and also nutritional recommendations. The objective of the present review is to provide a background and update on the current knowledge linking nutrition to cognition and behaviour in children, and to show how the large collaborative European Project NUTRIMENTHE is working towards this aim.