French doctors are puzzling over the case of 44-year-old civil servant who has led a quite normal life -- but with an extraordinarily tiny brain.
In a case history published in next Saturday's Lancet, doctors led by Lionel Feuillet of the Hopital de la Timone in Marseille say the father-of-two was admitted to hospital after suffering mild weakness in his left leg.
Scans by computed tomography (CT) and magnetic resonance imaging (MRI) showed that the man's cerebral cavities, called ventricles, had massively expanded.
"The brain itself, meaning the grey matter and white matter, was completely crushed against the sides of the skull," Feuillet told AFP.
"The images were most unusual... the brain was virtually absent," he said.
The patient's medical history showed that at the age of six months, he suffered hydrocephalus, also called water on the brain, and needed an operation to drain this dangerous buildup of spinal fluid.
Neuropsychological testing revealed the man had an IQ of 75, with a verbal IQ of 84 and performance IQ of 70. The bulk of people in society have a minimum IQ of 85, although the benchmark and the way it is measured are sometimes contested.
Despite this, "the man has been able to lead a life that can be considered normal," said Feuillet. "Even if he has a slight intellectual handicap, this has not hampered his development or building social networks."