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American Journal of Neuroradiology
DOI 10.3174/ajnr.A1792
PEDIATRICS
White Matter Impairment in Rett Syndrome: Diffusion Tensor Imaging Study with Clinical Correlations
From the Department of Internal Medicine (A.M.), University of Texas Medical Branch, Galveston, Texas; Department of Neurogenetics (G.B., S.N.), Hugo Moser Research Institute, Kennedy Krieger Institute, Johns Hopkins University, Baltimore, Maryland; F.M. Kirby Research Center (S.M.), Kennedy Krieger Institute, Johns Hopkins University, Baltimore, Maryland; Russell H. Morgan Department of Radiology and Radiological Science (I.I., L.F., A.H., S.M.), Johns Hopkins University, Baltimore, Maryland; Medical School (L.F.), Brasilia University, Brasilia, DF, Brazil; and Department of Radiology (A.-L.Z.), Zhangzhou Hospital of Fujian Medical University, Zhangzhou, Fujian Province, China.
Please address correspondence to Sakkubai Naidu, MD, 707 North Broadway, Baltimore, MD 21205; e-mail: naidu{at}kennedykrieger.org
BACKGROUND AND PURPOSE: RTT, caused by mutations in the methyl CPG binding protein 2 (MeCP2) gene, is a disorder of neuronal maturation and connections. Our aim was to prospectively examine FA by DTI and correlate this with certain clinical features in patients with RTT.
MATERIALS AND METHODS: Thirty-two patients with RTT underwent neurologic assessments and DTI. Thirty-seven age-matched healthy female control subjects were studied for comparison. With use of a 1.5T MR imaging unit, DTI data were acquired, and FA was evaluated to investigate multiple regional tract–specific abnormalities in patients with RTT.
RESULTS: In RTT, significant reductions in FA were noted in the genu and splenium of the corpus callosum and external capsule, with regions of significant reductions in the cingulate, internal capsule, posterior thalamic radiation, and frontal white matter. In contrast, FA of visual pathways was similar to control subjects. FA in the superior longitudinal fasciculus, which is associated with speech, was equal to control subjects in patients with preserved speech (phrases and sentences) (P = .542), whereas FA was reduced in those patients who were nonverbal or speaking only single words (P < .001). No correlations between FA values for tracts and clinical features such as seizures, gross or fine motor skills, and head circumference were identified.
CONCLUSIONS: DTI, a noninvasive technique to assess white matter tract pathologic features, may add specificity to the assessment of RTT clinical severity that is presently based on the classification of MeCP2 gene mutation and X-inactivation.
Abbreviations: SS, sagittal stratum