Low birthweight and preterm birth in young people with special educational needs: a magnetic resonance imaging analysis.

BACKGROUND: Although neuroanatomical and cognitive sequelae of low birthweight and preterm birth have been investigated, little is understood as to the likely prevalence of a history of low birthweight or preterm birth, or neuroanatomical correlates of such a history, within the special educational needs population. Our aim was to address these issues in a sample of young people receiving additional learning support. METHODS: One hundred and thirty-seven participants aged 13-22 years, receiving additional learning support, were recruited via their schools or colleges and underwent structural magnetic resonance imaging (MRI). Obstetric records, available in 98 cases, included birthweight and gestational data in 90 and 95 cases, respectively. Both qualitative and quantitative voxel-based analyses of MRI data were conducted. RESULTS: A history of low birthweight and preterm birth was present in 13.3% and 13.7% of cases, respectively. Low birthweight and preterm birth were associated with specific qualitative anomalies, including enlargement of subarachnoid cisterns and thinning of the corpus callosum. Low birthweight was associated with reduced grey matter density (GMD) in the superior temporal gyrus (STG) bilaterally, left inferior temporal gyrus and left insula. Prematurity of birth was associated with reduced GMD in the STG bilaterally, right inferior frontal gyrus and left cerebellar hemisphere. Comparison of subjects with no history of low birthweight or preterm birth with a previously defined control sample of cognitively unimpaired adolescents (n = 72) demonstrated significantly greater scores for several anomalies, including thinning of the corpus callosum, loss of white matter and abnormalities of shape of the lateral ventricles. CONCLUSION: Although a two-fold increased prevalence of a history of low birthweight and preterm birth exists within the special educational needs population, other aetiological factors must be considered for the overwhelming majority of cases. Neuroanatomical findings within this sample include qualitative anomalies of brain structure and grey matter deficits within temporal lobe structures and the cerebellum that persist into adolescence. These findings suggest a neurodevelopmental mechanism for the cognitive difficulties associated with these obstetric risk factors.

Qualitative assessment of brain anomalies in adolescents with mental retardation.

BACKGROUND AND PURPOSE: The neural basis of mental retardation is poorly understood. This study aimed to characterize structural anomalies of the brain in mental retardation and the relationship between them and the degree of mental retardation. METHODS: Eighty adolescents receiving educational support and 40 controls underwent MR brain imaging and intelligence quotient (IQ) assessment. MR images were evaluated according to a checklist of qualitative brain anomalies by a neuroradiologist blind to group membership. All scans were assessed by a second neuroradiologist to measure interobserver agreement. Ten percent of the studies were randomly selected for assessment of intraobserver agreement. RESULTS: Evaluation of MR images by using the checklist generated results with a high degree of interobserver and intraobserver agreement. Intraclass correlations were 0.93 and 0.75 for interobserver agreement on the total abnormality score and the entire checklist, respectively, and 0.97 and 0.85 for intraobserver agreement on the total abnormality score and the entire checklist, respectively. IQ is negatively correlated with the total abnormality score (P < .001). Subjects with an IQ <70 have a significantly greater total score (P = .003) and a significantly greater score for 12 specific anomalies, including thinning of the corpus callosum (P = .001) and abnormalities of the lateral ventricles. CONCLUSION: Mental retardation is associated with demonstrable brain anomalies, particularly thinning of the corpus callosum and ventricular abnormalities, and with a high total abnormality score. Greater levels of brain anomalies are associated with greater levels of mental retardation as evidenced by IQ.