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Biomedical subjects

François Chalard

Publications and source records attributed to François Chalard.

5 recordsLinked to original sources
PubMed2006

Microstructural development of human brain assessed in utero by diffusion tensor imaging.

BACKGROUND: Diffusion-weighted MR imaging (DWI) has been shown to be a great tool to assess white matter development in normal infants. Comparison of cerebral diffusion properties between preterm infants and fetuses of corresponding ages should assist in determining the impact of premature ex utero life on brain maturation. OBJECTIVE: To assess in utero maturation-dependent microstructural changes of fetal cerebral white matter using diffusion tensor MR imaging. MATERIALS AND METHODS: An echoplanar sequence with diffusion gradient (b=700 s/mm(2)) applied in six non-colinear directions was performed between 31 and 37(+3) weeks of gestation in 24 fetuses without cerebral abnormality on T1- and T2-weighted images. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured in the white matter. RESULTS: Mean ADC values were 1.8 microm(2)/ms in the centrum semiovale, 1.2 microm(2)/ms in the splenium of the corpus callosum and 1.1 microm(2)/ms in the pyramidal tract. The paired Wilcoxon rank test showed significant differences in ADC between these three white matter regions. Mean FA values were 1.1%, 3.8% and 4.7%, respectively, in the centrum semiovale, corpus callosum and pyramidal tract. A significant age-related decrease in ADC and an increase in FA towards term were demonstrated in the pyramidal tract and corpus callosum. CONCLUSION: Diffusion tensor imaging in utero can provide a quantitative assessment of the microstructural development of fetal white matter. Anisotropic parameters of the diffusion tensor should improve with technical advances.

Anisotropy↗
PubMed2006

A locus for sacral/anorectal malformations maps to 6q25.3 in a 0.3 Mb interval region.

Partial absence of the sacrum is a rare congenital defect that also occurs as an autosomal-dominant trait, whereas imperforate/ectopic anus is a relatively common malformation, usually observed in multiple congenital anomalies syndromes. We report on a girl born to healthy consanguineous parents (first cousins once removed) with anal imperforation and associated rectovaginal fistula and partial sacral agenesis. Facial dysmorphism included a high forehead, epicanthic folds, downslanting palpebral fissures, hypertelorism and a depressed nasal root. Brain MRI showed a bilateral opercular dysplasia with a unilateral (right) pachygyria; MRI and X-ray imaging of the spine disclosed a tethered cord associated with partial sacral agenesis. She showed a moderate developmental delay. Ophthalmologic examination evidenced bilateral microphthalmos and relative microcornea. Cytogenetic studies in our patient disclosed a pure de novo 6q25.3 --> qter deletion. By genotype analysis, we detected in our patient a maternal allele loss encompassing D6S363 and D6S446. Pure distal 6q deletion is a rare anomaly, reported in association with sacral/anorectal malformations (sacral agenesis, anal imperforation/ectopia) and never with cortical dysplasia. Pooling deletion mapping information in patients with pure terminal and interstitial 6q deletion allowed us to define a critical region spanning 0.3 Mb between the markers D6S959 and D6S437 for sacral/anal malformations. We hypothesize that haploinsufficiency for a gene within the deleted region may impair normal development of caudal structures, possibly acting on the notochordal development. European Journal of Human Genetics (2006) 14, 971-974. doi:10.1038/sj.ejhg.5201635; published online 17 May 2006.

Abnormalities, Multiple↗
PubMed2005

An atypical case of segmental spinal dysgenesis.

Spinal segmental dysgenesis is a complex closed dysraphism. The diagnostic criteria are: lumbar or thoracolumbar vertebral dysgenesis causing kyphosis, focal spinal cord narrowing without exiting roots, deformity of the lower limbs and paraplegia or paraparesis. We present a newborn who showed atypical features of bifocal spinal cord narrowing, without any vertebral abnormality at the proximal level. This seems to be a variant of this rare entity, whose early diagnosis is important, as surgical stabilisation of the spine is required.

Diagnostic Imaging↗
PubMed2004

Aortic dilatation in Turner syndrome: the role of MRI in early recognition.

BACKGROUND: Aortic dilatation and dissection are rare but important complications of Turner syndrome that increase the risk of sudden death in young patients. OBJECTIVE: To assess the value of aortic MRI in patients with Turner syndrome; in particular to demonstrate early aortic dilatation. MATERIALS AND METHODS: A total of 21 patients with Turner syndrome underwent MRI of the thoracic aorta with measurement of vessel diameter at four levels. RESULTS: Measurements were normal for age in 15 cases, two patients presented with values at the upper limit of normal and four had obvious dilatation of the ascending aorta. All were symptom free. CONCLUSIONS: MRI allows the non-invasive demonstration of early aortic dilatation, which may lead to earlier surgery in asymptomatic individuals.

Adolescent↗