Abstract
PurposeA retrospective study was performed to study the effect of fetal surgery on brain development measured by MRI in fetuses with myelomeningocele (MMC).MethodsMRI scans of 12 MMC fetuses before and after surgery were compared to 24 age-matched controls without central nervous system abnormalities. An automated super-resolution reconstruction technique generated isotropic brain volumes to mitigate 2D MRI fetal motion artefact. Unmyelinated white matter, cerebellum and ventricles were automatically segmented, and cerebral volume, shape and cortical folding were thereafter quantified. Biometric measures were calculated for cerebellar herniation level (CHL), clivus-supraocciput angle (CSO), transverse cerebellar diameter (TCD) and ventricular width (VW). Shape index (SI), a mathematical marker of gyrification, was derived. We compared cerebral volume, surface area and SI before and after MMC fetal surgery versus controls. We additionally identified any relationship between these outcomes and biometric measurements.ResultsMMC ventricular volume/week (mm3/week) increased after fetal surgery (median: 3699, interquartile range (IQR): 1651–5395) compared to controls (median: 648, IQR: 371–896); P = 0.015. The MMC SI is higher pre-operatively in all cerebral lobes in comparison to that in controls. Change in SI/week in MMC fetuses was higher in the left temporal lobe (median: 0.039, IQR: 0.021–0.054), left parietal lobe (median: 0.032, IQR: 0.023–0.039) and right occipital lobe (median: 0.027, IQR: 0.019–0.040) versus controls (P = 0.002 to 0.005). Ventricular volume (mm3) and VW (mm) (r = 0.64), cerebellar volume and TCD (r = 0.56) were moderately correlated.ConclusionsFollowing fetal myelomeningocele repair, brain volume, shape and SI were significantly different from normal in most cerebral layers. Morphological brain changes after fetal surgery are not limited to hindbrain herniation reversal. These findings may have neurocognitive outcome implications and require further evaluation.
Highlights
Myelomeningocele (MMC) is the most frequent form of open neural tube defect and results in abnormal development of the terminal spinal cord and associated meninges entailing an extrusion of the spinal cord into a cerebro-spinal fluid (CSF)–filled sac [1, 2]
Hydrocephalus requires treatment with ventriculoperitoneal shunts in up to 80% of cases and causes mechanical stretching of brain parenchyma leading to abnormal unmyelinated white matter development which can be illustrated in diffusion tensor imaging (DTI) studies [8,9,10,11,12,13,14,15]
We found that after accounting for differences in GA at time of magnetic resonance imaging (MRI) through calculating the paired change of volume and shape parameter/week, there were no significant differences when compared to GA-matched control fetuses without central nervous system (CNS) abnormalities
Summary
Myelomeningocele (MMC) is the most frequent form of open neural tube defect and results in abnormal development of the terminal spinal cord and associated meninges entailing an extrusion of the spinal cord into a cerebro-spinal fluid (CSF)–filled sac [1, 2]. Hydrocephalus requires treatment with ventriculoperitoneal shunts in up to 80% of cases and causes mechanical stretching of brain parenchyma leading to abnormal unmyelinated white matter development which can be illustrated in diffusion tensor imaging (DTI) studies [8,9,10,11,12,13,14,15] This neural tract damage can predispose to supratentorial anomalies such as altered gyrification patterns (e.g., polymicrogyria) and periventricular nodular heterotopia [8,9,10,11,12,13,14,15]. Mechanical compression of the cerebellum may lead to ischaemic changes compounding these deficiencies [8,9,10, 14]
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