Brain Injury in Fetuses with Vein of Galen Malformation and Nongalenic Arteriovenous Fistulas: Static Snapshot or a Portent of More?

Abstract

Background and purpose: Brain injury in fetuses with vein of Galen malformations and nongalenic AVFs is a rare complication whose appearance, course, and prognosis are poorly studied. We sought to characterize the MR imaging features and examine associations with postnatal outcome.

Materials and methods: This was a retrospective analysis of fetal MRIs of subjects with vein of Galen malformation and nongalenic arteriovenous fistulas. Two pediatric neuroradiologists independently reviewed examinations to determine the presence of abnormalities on structural imaging (T1 volumetric interpolated breath-hold examination and T2-HASTE), DWI, and T2*-weighted images; discrepancies were adjudicated by a third reviewer. Radiologic progression of injury was determined by additional fetal or neonatal MRIs. A simple composite score evaluating poor neonatal clinical outcome as either intubation or death by postnatal day 2 was also queried. A body fetal imager evaluated the presence of systemic findings of right heart strain.

Results: Forty-nine fetal MR imaging examinations corresponding to 31 subjects (27 vein of Galen malformations and 4 nongalenic AVF cases) were analyzed. Injury was observed in 8 subjects (26%) with 14 fetal examinations; the mean gestational age at identification of injury was 32.2 (SD 4.9) weeks. Structural abnormalities were present in all subjects with injury; restricted diffusion, in 5/7 subjects with available data; and T2* abnormalities, in all subjects with available data (n = 7). Radiologic progression was documented in all cases with follow-up imaging (n = 7). All subjects with fetal brain injury had a poor neonatal clinical outcome.

Conclusions: Brain injury in fetuses with vein of Galen malformation and nongalenic AVFs shows a combination of structural abnormalities, restricted diffusion, and blooming on T2* images. Injury appears to portend a poor prognosis, with relentless progression and a likely association with adverse neonatal outcomes.

FIG 1.

Structural abnormalities in fetuses with brain injury on T2- and T1-weighted images. A, Coronal T2 HASTE in a 35.3-week fetus (subject 5, scan 1) shows localized T2 prolongation (arrow), volume loss, and ventriculomegaly. B, Coronal T2 HASTE in a 21.9-week fetus (subject 3, scan 2) shows T2 hypointensity in the periventricular region (arrow). C, Coronal T2 HASTE shows periventricular cystic change (arrow) in a 29.4-week fetus (subject 2, scan 2). Coronal T2 HASTE (D) and coronal T1 VIBE (E) in a 33-week fetus (subject 6, scan 3) show generalized T2 prolongation and cerebral edema (asterisk), periventricular T2 hypointensity (arrow in D), and corresponding T1 hyperintensity (arrow in E).

FIG 2.

Abnormalities on T2*-weighted echo-planar sequences in fetuses with brain injury. A, Axial image in a 28.6-week fetus (subject 2, scan 1) shows blooming in the periventricular regions (arrows). B, Axial image in a 21.9-week fetus (subject 3, scan 2) shows blooming in the periventricular regions following the expected distribution of the proliferative compartments (germinal matrix [arrows]). C, Axial image in a 35.3-week fetus (subject 5, scan 1) shows generalized signal drop throughout the parenchyma.

FIG 3.

Diffusion abnormalities in fetuses with brain injury. ADC (A) and diffusion trace (B) in a 35.3-week fetus (subject 5, scan 1) show localized restricted diffusion in the left frontal lobe (arrows). ADC (C) and diffusion trace (D) in a 33-week fetus (subject 6, scan 3) show generalized restricted diffusion throughout the parenchyma (manual ROI measurements revealed ADC in C < 700 mm²/s in the deep gray nuclei and white matter).

FIG 4.

Progression of brain injury in 3 patients who underwent serial fetal MRIs. A and B, Subject 3, scan 1 and 2, at 20.4 weeks and then at 21.9 weeks when there is evidence of increased periventricular T2 hypointensity. C and D, Subject 2, scan 1 and 2, at 28.6 weeks and then at 29.4 weeks when there is evidence of a cystic change in the periventricular white matter and worsening of the T2 signal abnormality. E and F, Subject 6, scan 2 and 3, at 31.7 weeks and then at 33 weeks when there is generalized brain swelling and effacement of the extra-axial CSF in a pattern consistent with diffuse injury.