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Articles » Central nervous system » Holoprosencephaly » Alobar
2008-04-08-09 Alobar holoprosencephaly with proboscis © Werner
Alobar holoprosencephaly with proboscis 


Heron Werner, MD.

Clínica de Diagnóstico por Imagem – CDPI, Rio de Janeiro - Brazil.


Holoprosencephaly is a complex abnormality of the forebrain resulted from a failure of cleavage of the prosencephalon. Alobar holoprosencephaly is the most severe form characterized by the fused cerebral hemispheres, single primitive ventricle, fused thalami. The third ventricle, neurohypophysis, and olfactory bulbs are absent. The head is generally small.

Case report

We present a case of alobar holoprosencephaly with proboscis and cyclopia observed at 27 weeks of gestational age.

Figures 1, 2: Figure 1 shows axial ultrasound view of the fetal head with monoventricle and fused thalami. Figure 2 shows the same view obtained by MRI (T2-weighted). Note the proboscis in both figures (arrows).


Figure 3: Sagittal ultrasound view of the fetal head showing flat midface with absence of normal nose and prominent proboscis (arrow).

Figures 4, 5: 3D views of the fetal face showing the proboscis and cyclopia.


Figures 6, 7: Figure 6 shows sagittal T2-weighted view of the fetal head with monoventricle, proboscis (arrow) and hypoplastic cerebellum. Figure 7 shows the same MRI T1-weighted view.


Figure 8: Coronal T2-weighted view of the fetal head shows a monoventricle with a very thin mantle of brain and thalamic fusion.


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