In the past decades, multiple studies have been interested in developmental patterns of the visual system in healthy infants. During the first year of life, differential maturational changes have been observed between the Magnocellular (P) and the Parvocellular (P) visual pathways. However, few studies investigated P and M system development in infants born prematurely. The aim of the present study was to characterize P and M system maturational differences between healthy preterm and fullterm infants through a critical period of visual maturation: the first year of life. Using a cross-sectional design, high-density electroencephalogram (EEG) was recorded in 31 healthy preterms and 41 fullterm infants of 3, 6, or 12 months (corrected age for premature babies). Three visual stimulations varying in contrast and spatial frequency were presented to stimulate preferentially the M pathway, the P pathway, or both systems simultaneously during EEG recordings. Results from early visual evoked potentials in response to the stimulation that activates simultaneously both systems revealed longer N1 latencies and smaller P1 amplitudes in preterm infants compared to fullterms. Moreover, preterms showed longer N1 and P1 latencies in response to stimuli assessing the M pathway at 3 months. No differences between preterms and fullterms were found when using the preferential P system stimulation. In order to identify the cerebral generator of each visual response, distributed source analyses were computed in 12-month-old infants using LORETA. Source analysis demonstrated an activation of the parietal dorsal region in fullterm infants, in response to the preferential M pathway, which was not seen in the preterms. Overall, these findings suggest that the Magnocellular pathway development is affected in premature infants. Although our VEP results suggest that premature children overcome, at least partially, the visual developmental delay with time, source analyses reveal abnormal brain activation of the Magnocellular pathway at 12 months of age.
Objective: To determine by radiology the different etiologies of psychomotor delays (PMD) in Lomé (Togo). Material and Method: Retrospective study of 12 months in the radiology department of CAMPUS Teaching Hospital, concerned images of CT and MRI scans of children 0-16 years of age with PMD. Results: The mean age was 4.4 years +/-4.35. The result was pathological in 69.63% of the cases.Cerebral atrophy was the most frequent lesion (40.50%), followed by hydrocephalus (23.14%). The congenital stenosis of the Sylvius aqueduct was the most frequent malformation (37.93%). Triventricular hydrocephalus accounted for 45.61% of hydrocephalus. The most common tumor lesions were choroid plexus carcinoma and craniopharyngioma (28.57% each). Meningo-encephalitis accounted for half of infectious cases. Conclusion: PMD is most often the consequence of several cerebral pathologies. The most frequent of which is cerebral atrophy. L'âge moyen était de 4,4 ans +/-4,35. Le résultat était pathologique dans 69,63% des cas. L'atrophie cérébrale était la lésion la plus fréquente (40,50%), suivi des hydrocéphalies (23,14%). La sténose congénitale de l'aqueduc de Sylvius était la malformation la plus fréquente (37,93%). L'hydrocéphalie tri ventriculaire représentait 45,61 % des hydrocéphalies. Les lésions tumorales les plus retrouvées étaient le carcinome du plexus choroïde et le craniopharyngiome soit 28,57% chacun. Les méningo-encéphalites représentaient la moitié des atteintes infectieuses. Conclusion : Les RPM sont le plus souvent la conséquence de plusieurs pathologies cérébrales dont la plus fréquente l'imagerie est l'atrophie cérébrale.
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