Editorial for “3D Volumetric MRI Detects Early Alterations of the Brain Growth in Fetuses with Congenital Heart Disease”

Abstract

Editorial for “3D Volumetric MRI Detects Early Alterations of the Brain Growth in Fetuses with Congenital Heart Disease” Congenital heart disease (CHD), being the most common congenital malformation, causes the risk of neurodevelopmental disability in surviving children and a shift to cognitive impairment or dementia later in adulthood not only as a result of preoperative ischemic brain injury and surgical cardiac procedures’ adverse effects but also—or first of all—as a result of prenatal disturbances in brain development, with or without overt morphological injury. With the increasing number of survivors thanks to improved surgical techniques and intensive care, their neurodevelopmental deficits— considered the most important comorbidity and affecting patients with both simple and complex CHDs—constitute an important factor influencing their quality of life and society’s cumulative costs. Reduced cerebral oxygen and nutrient delivery, particularly inadequate glucose supply in CHD fetuses, are responsible for impaired brain development during fetal life, and even the most contemporary publications stress this in the third trimester of pregnancy, while it has been well established on ultrasound (US) that fetuses with CHD have a smaller head circumference (HC) and biparietal diameter from the second trimester of pregnancy onward and, recently, that those with cyanotic CHD have smaller HC from the first trimester, as early as 11–14 gestational weeks (GW), compared to age-matched controls. Magnetic resonance imaging (MRI), obviously, provides more detailed insight into the brain structure and volume than US; however, it is more affected by fetal motion. MRI allows for fetal brain segmentation and measurement of structures’ volumes, and three-dimensional (3D) volumetry is performed mostly in the third trimester, preferably near the end of pregnancy, when the fetus is least mobile and the segmentation is easiest to carry out. However, there are constant attempts to implement 3D segmentation and volumetry techniques in the earlier period of pregnancy, which have already enabled, for instance, the diagnosis of altered sulcal patterns in the left cerebral hemisphere of CHD fetuses compared with typically developing fetuses from 21 GW. An article by Ren et al in this issue of JMRI is part of this research trend. Their measurements were taken in the second trimester of pregnancy using slice-to-volume 3D reconstruction of single-shot turbo spin echo (SSTSE) imaging stacks and by quantifying cortical gray matter (GMV), subcortical brain tissue (SBV), intracranial cavity (ICV), lateral ventricles (VV), cerebellum, brainstem, and extracerebrospinal fluid (e-CSF) volumes by manual segmentation. Their results show that fetuses with CHD already in the second trimester have a statistically significant decrease in GMV, SBV, cerebellum, and brainstem volumes and statistically significant increase in e-CSF, e-CSF to ICV ratio, and VV when compared with normal fetuses after adjustment for gestational age (GA). Despite young GA, the shorter acquisition time of SSTSE sequence and postacquisition processing allowed for a decrease in the influence of motion artifacts on the final results, making it feasible to perform volumetric segmentation and measurements on MRI from mid-gestation. In recent years, there is an increasing number of papers devoted to the association of cerebellar damage with neurodevelopmental disability, and more and more attention is paid to the role of this damage in the development of autism spectrum disorders in premature children, etc. The findings of Ren et al confirm the previous, very few reports concerning impaired cerebellar growth in CDH fetuses, correlating with several neurodevelopmental deficiencies later in life. Moreover, in the study of Ren et al, five cardiac malformations are represented, namely, tetralogy of Fallot (TOF), transposition of the great arteries, pulmonary stenosis, double outlet right ventricle, and hypoplastic left heart syndrome (HLHS). This heterogeneity of the study group is an advantage rather than a limitation taking into account the fact that previous studies concerned homogeneous groups of fetuses with TOF and HLHS. In one of them, similarly, younger fetuses were examined, and smaller volumes of gray and white matter and larger volumes of cerebrospinal fluid spaces were also shown at the GA of ≤25 weeks, thus indicating an earlier start of changes in TOF patients. The results of Ren et al confirm that all CHDs cause similar inhibition of fetal brain growth. One limitation of the study is the relatively low number of cases being analyzed. Nevertheless, these encouraging results open the avenue to establish fetal MRI as a feasible method to monitor fetal brain growth in fetuses with CHD and other