1052: Brain composition differences in fetuses after laser surgery for twin-twin transfusion syndrome (TTTS)

Abstract

We describe the maturational pattern differences of various brain tissues between donor versus recipient twins treated with in utero laser surgery for TTTS using 3D MRI reconstruction. This was a prospective study of 20 patients with TTTS and dual survivors 4 weeks postoperatively. Fetal MRI scans were performed with a 1.5-T scanner. Multiple stacks of singleshot fast spin-echo T2-weighted slices of the fetal brain were obtained in the axial, sagittal, and coronal planes for each fetus. The images were reconstructed into 3D MRI volumes after motion correction. Total brain volume (TBV), cortical plate region (CR), developing white matter region (WMR), cerebellum, and ventricles were delineated using a semi-automated, atlas based segmentation method (Figure 1(a)). CR, WMR, cerebellum, and ventricular volumes were normalized by TBV for each subject. The CR and WMR were additionally normalized to the supratentorial structures only, called total parenchymal volume (TPV). Relationship between gestational age (GA), twin status (donor/recipient) and normalized tissue volumes were modeled using robust, multiple linear regression and tested for significance (defined as p<0.05). Eighteen of 20 twin pairs had sufficient image quality for analysis. The median gestational age (GA) at laser surgery was 19.8 (16.4-26.4) weeks, and 25.1 (22.1-30.7) weeks at MRI examination. Figure 1 (b-f) shows the comparative relationship between normalized tissue volumes and gestational age between the donor and recipient twin pairs. TBV was significantly lower in the donor twins (Figure 1b), although TPV were not different between the twin pairs (Figure 1c). Recipients showed significantly lower proportions of CR and cerebellar volumes normalized to TBV compared to donors (Figure 1d,e). Ventricular volumes normalized to TBV were significantly higher in the donor twins (Figure 1f). No significant differences were detected in WMR volumes between the two groups. Recipients showed significantly lower proportions of CR normalized to TPV compared to donors. Although the total brain volume of the donor twin was smaller than that of the recipient twin, the proportional brain tissue volumes of the donor were preserved. Rather, it was the recipient twin that had relatively reduced proportions of cortical plate region and cerebellar volumes.