Selective Cerebral Volume Reduction in Rett Syndrome: A Multiple-Approach MR Imaging Study

J.C. Carter; D.C. Lanham; D. Pham; G. Bibat; S. Naidu; W.E. Kaufmann

doi:10.3174/ajnr.A0857

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Fig 1.
Concordance of Talairach and voxel-based findings in the posterior dorsal parietal lobe in RTT versus control subjects. Talairach-derived data (top row) show preferential bilateral reduction of GM in the posterior dorsal parietal lobe (outlined; only left side shown), corresponding with Brodmann areas 5 and 7. Similarly, VBM-derived data (bottom row) show bilateral GM volume reduction in the posterior dorsal parietal region (outlined), roughly corresponding with Brodmann area 7 (left hemisphere differences are depicted here).
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Fig 2.
Concordance of Talairach and voxel-based findings in the prefrontal GM in more severe versus less severe RTT subjects. Girls with less severe clinical presentation, according to gait abnormality criterion, showed relative preservation of prefrontal GM volumes, corresponding roughly with Brodmann areas 10/46. A, Top left depicts Talairach-derived data, whereas bottom left shows VBM-derived data. B, Boxplots (percentiles) of Talairach-based prefrontal GM volumes illustrate that girls with less severe clinical presentation show volumes intermediate between control subjects and those with more severe phenotype.
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Fig 3.
Cerebral lobar GM volumes in monozygotic twins discordant for the RTT phenotype. Note that the unaffected twin showed frontal, parietal, and temporal GM volumes within the normal control range (depicted as mean +1 SD), whereas the affected twin had smaller volumes in these regions, with the exception of the occipital GM volume, which was at nearly identical levels in both twins and only slightly below the normal control range.

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Table 1:

Demographic and clinical characteristics of the study cohort

Variable	n	Age, Mean ± SD, y	Head Circumference, Mean ± SD, cm	Clinical Severity Scores, Mean ± SD
Variable	n	Age, Mean ± SD, y	Head Circumference, Mean ± SD, cm	Total	Head Growth	Seizures	Respiratory Irregularities	Scoliosis	Gait Abnormalities
All RTT subjects	22	8.6 ± 1.8	49.5 ± 2.1	7.8 ± 2.4	2.5 ± 0.8	1.2 ± 1.0	1.7 ± 0.8	0.7 ± 1.0	1.6 ± 1.0
Affected MZ twin		8.4	50.5	8	3	1	2	0	2
More severe (gait criterion)	12	8.8 ± 1.6	49.3 ± 2.4	9.6 ± 1.3^*	2.6 ± 0.7	1.4 ± 1.0	1.8 ± 0.8	1.7 ± 1.2^*	2.4 ± 0.7^*
Less severe (gait criterion)	10	8.3 ± 2.1	49.4 ± 1.8	5.9 ± 1.5	2.5 ± 1.0	1.0 ± 1.1	1.6 ± 0.8	0.1 ± 0.3	0.7 ± 0.7
Control subjects	25	8.9 ± 1.9

Note:—RTT indicates Rett syndrome; MZ, monozygotic. Age represents age at time of MR imaging scan. The maximum total clinical severity score is 15. The “more severe” group included the following mutations: R106W (n = 1), T158M (n = 3), R255X (n = 1), R270X (n = 2), R294X (n = 2), and C-terminal deletions (n = 3). The “less severe” group included the following mutations: R133C (n = 1), R168X (n = 1), R255X (n = 1), R294X (n = 4), R306C (n = 2), and G451T/D151Y (n = 1 each).
* P < .05 when comparing more severe versus less severe gait.