Les dysplasies cérébelleuses : corrélations anatomo-fonctionnelles

Abstract : Cerebellar dysplasia is a developmental anomaly involving mainly the cerebellum, resulting in a focal or diffuse macroscopic and microscopic disruption of the tissue architecture. Previous studies have well documented the magnetic resonance imaging (MRI) features of this malformation. However, the impact of cerebellar dysplasia, which may be associated with other developmental anomalies of the central nervous system (CNS), on the cognitive development and function, is ill known and poorly documented. We aimed to study the structural functional correlations in this cerebellar malformation, by investigating the neuropsychological, genetic and, functional disturbances associated as well as the neuroanatomical approach. Our work was conducted in 4 directions including 3 different populations. First, we assessed the neuropsychological profile and the follow-up of children with isolated cerebellar dysplasia (ICD). We observed I this population a wide range of neuropsychological expression of ICD, from normal efficiency to severe mental retardation, without no correlation with the degree of dysplasia. Moreover, during the follow-up of these children, we noticed the unpredictable heterogeneity of the cognitive evolution with the emergence in some cases of certain function such as language. Secondly, we investigated the CNS function using fluorodeoxyglucose positron emission tomography (FDG-PET) in six children with ICD. The results showed within the cerebellum a normal aspect in patients with minor dysplasia (restricted to the vermis), a hypometabolism in dysplastic zones (correlating with the anatomical extent), and a metabolism similar to that of the cortex in heterotopias. Nevertheless, these functional disturbances were not correlated with neuropsychological impairement. Thirdly, we attempted to investigate the genetic abnormalities leading to the embryology physiopathology basis of cerebellar dysplasias associated (CDA) with Lissencephalies (smooth brain). The quite well characterized genetics of human brain lissencephalies have allowed us to identify some genes involved in the neuronal and axonal migration process (RELN and VLDLR) to be significantly associated with cerebellar dysplasia, not including CDA in muscular dystrophy syndromes related to O-glycosylation defects. Fourthly, we aimed to find in normal volunteers the neuroanatomical potential markers of cognitive disturbances associated with cerebellar dysplasia, on the hypothesis that an isolated cerebellar malformation could induce some anomalies on the pathways of cerebello-cortical projections, detectable by diffusion tensor imaging (DTI). These pathways are presumably involved in the cerebellar implication in higher functions. This work has allowed us to visualize and quantify selectively the cerebello-cortical projections to the prefrontal and parietal cortices in the normal human brain. Thus, our overall results have permitted: (i) to clearly assess the neuropsychological disturbances associated with ICD and their heterogeneity, both at the time of diagnosis and at the follow-up, (ii) to correlate the cerebellar dysplasia to brain glucose uptake differences and subsequently to brain dysfunction, (iii) to suggest some precise genetic analyses in neuronal and axonal migration pathways, and eventually, (iv) to obtain some anatomical markers which we can apply to dysplastic patients in order to assess the putative disruption of cerebello-cortical projections. Thereby, our results have opened numerous perspectives in applying advanced anatomical and functional neuroimaging techniques to the cerebellar dysplastic patients.
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Life Sciences [q-bio]. Université du Droit et de la Santé - Lille II, 2011. French. <NNT : 2011LIL2S006>


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Patrice Jissendi Tchofo. Les dysplasies cérébelleuses : corrélations anatomo-fonctionnelles. Life Sciences [q-bio]. Université du Droit et de la Santé - Lille II, 2011. French. <NNT : 2011LIL2S006>. <tel-00635755>

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