A man with an unusually tiny brain manages to live an entirely normal life despite his condition, which was caused by a fluid build-up in his skull.

Scans of the 44-year-old man's brain showed that a huge fluid-filled chamber called a ventricle took up most of the room in his skull, leaving little more than a thin sheet of actual brain tissue (see image, right).

"It is hard for me [to say] exactly the percentage of reduction of the brain, since we did not use software to measure its volume. But visually, it is more than a 50% to 75% reduction," says Lionel Feuillet, a neurologist at the Mediterranean University in Marseille, France.

Feuillet and his colleagues describe the case of this patient in The Lancet. He is a married father of two children, and works as a civil servant.