The neurologist at the University of Marseille followed the obvious course of action. His 44 year old patient had complained of a weakness in his left leg so he sent him for a brain scan. When the doctor saw the magnetic resonance image of the man’s brain, he was stunned. In fact there was not much of a brain to be seen. Most of the skull cavity was taken up by fluid, with a smattering of brain tissue lining the inside of the skull. The man should have been severely resulted, and yet he was not mentally disabled, holding down a job as a civil servant. Subsequent tests showed his IQ to be below normal which had not impaired his ability to carry out tasks at the local tax office where he was employed. As can be expected, the story generated a great deal of press coverage with headline writers vying to outdo each other with their cleverness. “Tiny brain no problem for French tax official” and “man lives normal life with abnormal brain” were typical examples. The man’s head was filled with cerebrospinal fluid which normally bathes the brain and spinal cord and accumulates in cavities in the brain called ventricles. In a condition known as hydrocephalus, so much fluid accumulates that the ventricles greatly expand and squish the brain aside. Commonly known as “water on the brain,” hydrocephalus is a birth defect that usually causes mental impairment and results in an abnormally large skull due to the extra internal pressure applied to the skull as it forms. The French patient had been born with hydrocephalus and was surgically treated as an infant by implanting a shunt into the brain to drain away excess fluid into the blood. He had developed essentially normally oblivious of the fact that his head was essentially filled with fluid until the problem with his leg cropped up. A neurosurgeon now inserted another shunt and within weeks the man’s neurological problems disappeared and he was back at work in the tax office.
The story is remarkable but not unique. Back in 1980, an article appeared in Science, one of the world’s top journals, describing the work of John Lorber, a professor of pediatrics at University of Sheffield in England who had conducted a number of studies on individuals who were afflicted with hydrocephalus and came up with some remarkable findings. Lorber had subjected his patients to CAT scans and found that while most of them were mentally impaired, some, even when their brain filled no more than 5% of the cranial cavity led normal lives. In one documented case, a colleague referred a young man to Lorber because of his unusually large head which apparently was not causing him any difficulty. A CAT scan revealed a skull lined with about a millimeter thick layer of brain tissue and filled with cerebrospinal fluid. Of course the brain stem which sits at the bottom of the brain and connects to the spine was normal. Since it controls vital functions such as breathing, swallowing, digestion, eye movement and heartbeat, there can be no life without it. But the rest of the brain is obviously capable of some remarkable feats, with one part able to compensate for deficiencies in another. In the case of the young man who Lorber investigated, the thin layer of brain cells was certainly up to the task of providing the necessary brain power. The student had a high IQ of 126 and had a first class honours degree in mathematics. It seems you don’t need much of a brain to do mathematics.