Extension to one week of verbal memory consolidation assessment

Objective: In the absence of physical characteristics of Fetal Alcohol Syndrome (FAS), etiologic diagnosis of non-syndromic forms of Fetal Alcohol Spectrum Disorders (NS-FASD) remains probabilistic. Moreover, there are few prognostic markers. Cerebral growth deficiency is the most obvious and constant neuroanatomic abnormality in FASD. In order to identify new neuroanatomic markers useful for diagnosis or prognosis, we assessed whether the distribution of this reduction in total brain volume (TBV) was harmonious or not, at a lobar and cerebellar level, taking into account physiological allometry (variations in proportions and shape related to size variations). Methods: We analyzed 3DT1 MRI from 37 FASD and 36 controls (6–26 years old). We segmented hemispheres, lobes, deep brain and cerebellum with 2 methods (#1: using spatial normalization and atlas, #2: without normalization and with spectral-based parcellation). Relationship between regional volume and TBV was assessed using a simple proportional model (b.TBV) or a scaling model (b.TBVˆa) that is known to better describe allometric phenomena. Comparisons were done with a threshold p-value of 0.005, taking into account multiple testing. Results: TBV, cerebellar and lobar volumes were all smaller in FASD than in controls. With a simple proportional model, there was no regional difference between groups, otherwise inconsistent between segmentations (temporal #1). With a scaling model, scaling exponent was significantly higher in the FASD group for cerebellum (#1 1.14 vs. 0.61; #2 1.18 vs. 0.60 p <0.005) and deep brain. Conversely, scaling exponent was slightly smaller for the FASD hemispheres (complementary volumes). Trends observed for the lobes were not significant or inconsistent between segmentations (occipital #2). Conclusion: Thus, we identified a new neuroanatomic marker related to a spatial heterogeneity of cerebral growth deficiency: typical negative allometry of the cerebellum is disturbed in FASD. Further analysis of the diagnosis and prognosis values of this marker is in progress.

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