What is the striking abnormality?
Microcephaly. Only striking when you see it.
On antenatal ultrasound how does one define microcephaly?
One should use head circumference (not bi-parietal distance). The size should be below the 3rd centile, provided the rest of the foetus has normal size for gestation (otherwise you may merely have IUGR / small for dates).
This patient happens to have Rubinstein-Taybi syndrome. For bonus radiology geek points, can you name the features of this rare and obscure syndrome?
Rubinstein-Taybi syndrome is characterized by mental retardation, broad and often angulated thumbs and halluces, and distinctive facial features. Read more about it in the related article.
Non contrast CT of the brain and face demonstrates swelling over the left orbit without fracture. There is marked microcephaly with thickening of the skull. The nose is large, beaked with the a broad base.