Dolors Segarra

Hippocampal gray matter reduction associates with memory deficits in adolescents with history of prematurity

Using optimized voxel-based morphometry (VBM), we compared the relationship between hippocampal and thalamic gray matter loss and memory impairment in 22 adolescents with history of prematurity (HP) and 22 normal controls. We observed significant differences between groups in verbal learning and verbal recognition, but not in visual memory. VBM analysis showed significant left hippocampal and bilateral thalamic reductions in HP subjects. Using stereological methods, we also observed a reduction in hippocampal volume, with left posterior predominance. We found correlations between left hippocampal gray matter reductions (assessed by VBM) and verbal memory (learning and percentage of memory loss) in the premature group. The stereological analysis showed a correlation between verbal learning and the left posterior hippocampus. Our results suggest that left hippocampal tissue loss may be responsible for memory impairment and is probably related to the learning disabilities that HP subjects present during schooling.

Corpus Callosum and Prefrontal Functions in Adolescents with History of Very Preterm Birth.

Very preterm (VPT) birth can account for thinning of the corpus callosum and poorer cognitive performance. Research findings about preterm and VPT adolescents usually describe a small posterior corpus callosum, although our research group has also found reductions of the anterior part, specifically the genu. The aim of the present study was to investigate the functional implications of this concrete reduction. Fifty-two VPT adolescents were compared with 52 adolescents born at term; there were no significant differences in age and gender, and socioeconomic status was similar between the groups. All participants underwent a magnetic resonance imaging (MRI) study and assessment of prefrontal functioning and vocabulary. The VPT group showed significant reductions of the genu, isthmus and splenium, as well as a significantly worse performance on category verbal fluency, executive functions, everyday memory and vocabulary. Although several parts of the corpus callosum correlated with some prefrontal functions, the genu was the part which principally explained these correlations. The subtest Vocabulary only correlated with the splenium. The relationship between genu and prefrontal functions and between splenium and vocabulary may be due to the fact that these parts of the corpus callosum connect prefrontal and posterior parietal cortex, respectively. The work presented here provides evidence of specific associations between reductions in the anterior corpus callosum (genu) and lower prefrontal functioning in VPT adolescents.

Gestational Age at Preterm Birth in Relation to Corpus Callosum and General Cognitive Outcome in Adolescents

Prematurity is associated with corpus callosum abnormalities and low general cognitive functioning. The present study explores the specific relationship between gestational age, corpus callosum, and intelligence quotient (IQ) in a sample of preterm-born adolescents. Sixty-four adolescents born at a gestational age of 36 weeks or less were divided into 4 groups attending to their gestational age (GA) (group 1, ≤ 27; group 2, 28-30; group 3, 31-33; group 4, 34-36). These individuals were compared with 53 adolescents born at term and of similar age, gender, and sociocultural status. Individuals born at a gestational age of 27 or less (group 1) presented a generalized corpus callosum reduction in the posterior part (posterior midbody, isthmus, and splenium) as well as in the anterior part (anterior midbody and genu), a reduced total white-matter volume, and a low Full-Scale IQ. Group 2 (GA between 28 and 30) also showed a low IQ, but corpus callosum reduction was only found in the splenium, without total white-matter volume reductions. Group 3 (GA between 31 and 33) did not present differences in corpus callosum size or a reduced total white- matter volume, but they showed a low Full-Scale IQ. Group 4 (GA between 34 and 36) did not show a smaller corpus callosum or a lower general cognitive performance. Specific significant correlations were found between corpus callosum subregions and gestational age. These results suggest the importance of gestational age in prematurity in relation to brain structural and functional outcome. Premature babies born at a gestational age of 27 weeks or less are the target group for long-term corpus callosum and white-matter anomalies and for a low IQ.

Neuropsychologic Impairment in Bilateral Cerebral Palsy

The lower-than-average cognitive performance of individuals with bilateral cerebral palsy found in previous studies does not always refer to an abnormal performance or clinically significant impairment. We aimed to establish the percentage of persons with bilateral cerebral palsy who present neuropsychologic impairment, and its relationship to perinatal data and motor signs. Forty children, adolescents, and adults (age range, 6-38 years; 15 females and 25 males) with bilateral cerebral palsy were neuropsychologically assessed. Vocabulary was impaired in 85% of participants, language comprehension in 13-48%, visuoperceptual abilities in 60%, visuospatial abilities in 90%, short-term memory in 21-58%, declarative memory in 47-67%, and praxis comprehension in 20%, with executive deficits in 58-74%. Perinatal data (intrauterine growth and birth weight) contributed to explaining memory impairment. Among cerebral palsy subtypes (spastic, mixed, and dyskinetic), forms of impairment differed only in short-term verbal memory. No persons with dyskinetic cerebral palsy experienced impairment in immediate memory or working visual memory. We conclude that visuospatial deficit is the most frequent impairment in people with bilateral cerebral palsy. Moreover, short-term memory impairment seems sensitive to perinatal complications, and differs among bilateral cerebral palsy subtypes.

Raven's Coloured Progressive Matrices as a Measure of Cognitive Functioning in Cerebral Palsy.

BACKGROUND Cognitive dysfunction is frequent in Cerebral Palsy (CP). CP motor impairment and associated speech deficits often hinder cognitive assessment, with the result being that not all CP studies consider cognitive dysfunction. Ravens Coloured Progressive Matrices is a simple, rapid test which can be used in persons with severe motor impairment and speech limitations. We studied whether this test can offer a reliable measure of cognitive functioning in CP. METHOD Visuoperceptual, language, memory and frontal lobe functions were evaluated in 30 participants with severe motor impaired CP and a variety of speech difficulties. The relationship between Ravens Coloured Progressive Matrices and a variety of tests was analysed. RESULTS Ravens Coloured Progressive Matrices performance was associated with visuoperceptual, language, visual and verbal memory but not with frontal functions. Receptive vocabulary and visuospatial measures were the best predictors of Ravens Coloured Progressive Matrices raw scores. CONCLUSIONS Ravens Coloured Progressive Matrices is a fast, easy-to-administer test able to obtain a measure related with linguistic, visuoperceptual, and memory cognitive functioning in persons with CP despite their motor and speech disorders.

Cortical Thickness and Behavior Abnormalities in Children Born Preterm

Aim To identify long-term effects of preterm birth and of periventricular leukomalacia (PVL) on cortical thickness (CTh). To study the relationship between CTh and cognitive-behavioral abnormalities. Methods We performed brain magnetic resonance imaging on 22 preterm children with PVL, 14 preterm children with no evidence of PVL and 22 full-term peers. T1-weighted images were analyzed with FreeSurfer software. All participants underwent cognitive and behavioral assessments by means of the Wechsler Intelligence Scales for Children-Fourth Edition (WISC-IV) and the Child Behavior Checklist (CBCL). Results We did not find global CTh differences between the groups. However, a thinner cortex was found in left postcentral, supramarginal, and caudal middle rostral gyri in preterm children with no evidence of PVL than in the full-term controls, while PVL preterm children showed thicker cortex in right pericalcarine and left rostral middle frontal areas than in preterm children with no evidence of PVL. In the PVL group, internalizing and externalizing scores correlated mainly with CTh in frontal areas. Attentional scores were found to be higher in PVL and correlated with CTh increments in right frontal areas. Interpretation The preterm group with no evidence of PVL, when compared with full-term children, showed evidence of a different pattern of regional thinning in the cortical gray matter. In turn, PVL preterm children exhibited atypical increases in CTh that may underlie their prevalent behavioral problems.

Thalamic changes in a preterm sample with periventricular leukomalacia: correlation with white-matter integrity and cognitive outcome at school age

Introduction:Thalamic abnormalities have been well documented in preterms with periventricular leukomalacia (PVL), although their contribution to long-term cognitive dysfunctions has not been thoroughly investigated.Results:Significant differences between groups were observed for global thalamic volume. Neuropsychological assessments showed that preterms with PVL scored within the normal range, although significantly below controls in the full intelligence quotient and the specific cognitive domains of processing speed and working memory. Correlations of several thalamic regions with Working Memory Index and FIQ were found in the PVL group. Moreover, thalamic atrophy correlated with white-matter (WM) damage indexes (fractional anisotropy and radial diffusivity) assessed by diffusion tensor imaging.Discussion:The findings suggest that thalamic damage is a common correlate of WM microstructural alterations and might be involved in the cognitive deficits seen in premature infants with PVL at school age.Methods:We analyzed the impact of PVL-associated thalamic injury on cognitive status at school age and its correlation with WM integrity as measured by magnetic resonance imaging techniques. Thalamic volume and shape of 21 preterm children with PVL were compared with those of 11 preterm children of similar gestational age and birth weight with no evidence of focal WM abnormality.

Gray Matter Volume Decrements in Preterm Children With Periventricular Leukomalacia

Periventricular leukomalacia (PVL) is the prototypic lesion in the encephalopathy of prematurity. Although PVL is identified by targeting cerebral white matter (WM), neuropathological and MRI studies document gray matter (GM) loss in cortical and subcortical structures. This study aimed to investigate the distribution of GM changes in children with a history of premature birth and PVL. Voxel-based morphometry was used to examine regional GM abnormalities in 22 children with a history of preterm birth and PVL. Preterms with PVL were compared with 22 terms and 14 preterms without PVL of similar GA and birth weight. GM and WM global volumetric volumes were found to decrease in comparison with both control groups. Regional GM volume abnormalities were also found: compared with their term peers, preterm children with PVL showed several regions of GM reduction. Moreover, PVL differed from preterms without PVL in the medial temporal lobe bilaterally, thalamus bilaterally, and caudate nuclei bilaterally. In addition, in our preterm sample with PVL, birth weight showed a statistical significant correlation with decreased GM regions. In conclusion, the voxel-based morphometry methodology revealed that PVL per se does involve GM reductions.

Memory Performance in a Sample of Very Low Birth Weight Adolescents

Prematurely born participants with very low birth weight (VLBW) are at high risk of brain injury in the perinatal period and of later cognitive impairment. Studies of long-term memory sequelae in VLBW participants are scarce and focus on verbal and visual memory assessed by standard clinical memory tests. There is even less research into everyday memory, and the results obtained are contradictory. This study explores long-term memory deficits in VLBW adolescents using 2 standard clinical memory tests and 1 everyday memory test. Results show impairment only in everyday memory. These memory deficits are not specific; they are related to an impaired general cognitive performance. Unlike birth weight, gestational age is a good predictor of intelligence.

Medial temporal MR spectroscopy is related to memory performance in normal adolescent subjects

In addition to the study of pathological conditions, magnetic resonance spectroscopy can provide useful information about brain–behavior relationships in normal subjects. Recently, there have been reports of correlations between N-acetylaspartate (NAA) values and cognitive functions in normal adults. We tested the possible specific relationship between the NAA/choline (Cho) ratio in the medial temporal lobe and memory performance in normal adolescents. The medial temporal NAA/Cho ratio was unrelated to age, gender and general intelligence but presented a clear correlation with several memory measures. In the regression analysis two memory variables (RAVLT learning and a face–name recognition task) explained 55.6% of NAA/Cho variance. We conclude that NAA values in the medial temporal lobe are related to memory abilities but not to global intelligence in normal adolescent subjects.