Agenesis of the corpus callosum: an MR imaging analysis of associated abnormalities in the fetus

Abstract

Background and purpose: Anomalies associated with callosal agenesis (ACC) found postnatally have been well documented. However, to our knowledge, no detailed MR imaging analysis of associated anomalies has been reported in a large cohort of fetuses with ACC. This study will assess those anomalies and compare them with postnatal cohorts of ACC, to identify associated fetal brain abnormalities that may give insight into etiology and outcome.

Materials and methods: All cases of ACC diagnosed on fetal MR imaging during an 11-year period were retrospectively reviewed, including fetal MR imaging, postnatal MR imaging, and autopsy findings. Neurodevelopmental outcome was classified as poor in children with seizures and/or severe neurodevelopmental impairment or in cases of neonatal death.

Results: Twenty-nine cases of ACC were identified. Median gestational age was 26.14 weeks (range, 19.71-36.43 weeks). Twenty-three fetuses had delayed sulcation and/or too-numerous cortical infoldings (abnormal morphology). Fifteen fetuses had cerebellar and/or brain stem abnormalities. Fetal MR imaging findings suggested a genetic syndrome in 5 fetuses and an acquired etiology or genetic/metabolic disorder in 2 fetuses. Findings were confirmed in 8 cases with postnatal MR imaging, except for delayed sulcation and small vermis, and in 4 cases with autopsy, except for periventricular nodular heterotopia and abnormalities in areas not examined by autopsy. Neurodevelopmental outcome was good in 7 and poor in 9 children. Abnormal sulcal morphology and/or infratentorial abnormalities were present in those with poor outcome and absent in those with good outcome.

Conclusions: ACC is infrequently isolated in fetuses. Abnormal sulcation is common and suggests more diffuse white matter dysgenesis in these fetuses.

Figures

Fig 1.

Patient 20: 28.86-gestational-week fetus. A, Axial image demonstrates numerous abnormal cortical infoldings (black arrows) in the right hemisphere with a shallow left Sylvian fissure (arrowhead). B, Coronal image demonstrates an area of hypointensity (arrow) underlying the abnormal cortical infoldings.

Fig 2.

Patient 7: 22-gestational-week fetus. A, Sagittal image demonstrates multiple abnormal infoldings of the cortex (black arrows). The lateral ventricle is dysplastic with multiple undulations along its margin. Periventricular nodular heterotopia are seen (white arrows). The multilayered pattern of the supratentorial parenchyma is absent. B, Coronal image demonstrates abnormal infoldings of both frontal lobes with the left frontal lobe extending across the midline and dilated dysplastic frontal horns bilaterally. A diagnosis of Aicardi syndrome was confirmed postnatally.

Fig 3.

Patient 3: 21-gestational-week fetus. Axial image demonstrates areas of hypointensity and hyperintensity involving the deep gray nuclei bilaterally (arrowheads), consistent with areas of hemorrhage and necrosis. There is bilateral ventriculomegaly with diffuse thinning of the parenchyma, with areas of hypointensity in the occipital and parietal lobes (arrows).

Fig 4.

Patient 10: 23-gestational-week fetus. Axial image demonstrates small abnormally shaped deep gray nuclei (arrows). The Sylvian fissures are absent, and there is diffuse thinning and hypointensity of the parenchyma. A diagnosis of Walker-Warburg syndrome was confirmed by autopsy.

Fig 5.

Patient 29: 36.43-gestational-week fetus. Axial image demonstrates bilateral periventricular nodular heterotopia (black arrows) and mild ventriculomegaly.

Fig 6.

Patient 28: 36-gestational-week fetus. A, Coronal image demonstrates a small left cerebellar hemisphere (arrow). The sulcation pattern is also diffusely abnormal with too-numerous infoldings of the cortex bilaterally. B, Sagittal image demonstrates a small pons (white arrow) and a small vermis (black arrow) as well as ACC.

Fig 7.

Patient 16: 26.43-gestational-week fetus. A, Axial image demonstrates absence of the central sulci, which should be present at this gestational age. B, Coronal image demonstrates ACC as well as prominence of the temporal horns (the atria were mildly dilated as well) and absence of the collateral sulci, which should normally be present at this gestational age. C, Axial image from follow-up fetal MR imaging performed at 32.43 gestational weeks demonstrates a normal appearance of the sulci for gestational age, including formation of the central sulci bilaterally (white arrows), precentral sulci bilaterally (black arrows), and postcentral sulci bilaterally (arrowheads). D, Coronal image at 32.43 gestational weeks demonstrates interval development of the collateral sulci bilaterally (black arrows), superior temporal sulci bilaterally (arrowheads), and inferior temporal sulcus on the left (white arrow).