What is hydrocephaly?

Hydrocephaly or hydrocephalus - also known as ‘water on the brain’ is a brain disease that affects 1 in every 500 births, making it one of the most common developmental disabilities - more common than Down syndrome or deafness. It was first described by Hippocrates, the ancient Greek physician. It wasn’t until the 20th century that effective treatments were developed for it, and there is still no known cure.

So what is it?

Our brains are suspended in a bath of fluid called cerebrospinal fluid. In hydrocephaly, pockets of this fluid in the brain called ventricles expand like balloons, pushing into the brain tissue. It can cause convulsions, mental retardation and death. In the worst cases 95% of the skull is filled with cerebrospinal fluid and all that is left of the normal 1.5kg brain is a thin layer of 50-100g rind pressed up against the skull.

The British neurologist John Lorber documented over 600 scans of people with hydrocephaly, and he made an extraordinary discovery. Among those in the most severe category of 95% or more fluid, half were severely retarded. But the other half were found to have IQ’s greater than 100. One young man in the category of ‘virtually no brain whatsoever’ was recorded to have an IQ of 126. He got a first class honors degree in mathematics.

Below is an MRI scan of an individual with hydrocephaly. The region labeled LV is just fluid in this brain - normally it is packed with neural tissue. Anyone looking at this image would naturally conclude that the poor man was (a) dead or (b) a vegetable.

Hydrocephaly and brain plasticity

Image: Feuillet et al/The Lancet

But in point of fact this 44 year old French man was living a normal life. “He was a married father of 2 children, and worked as a civil servant,” Dr Lionel Feuillet and colleagues at the Universite de la Mediterranee in Marseille wrote in a letter to the The Lancet medical journal.

What explains hydrocephaly? Brain plasticity?

Brain plasticity is the ability of the brain to reorganize itself – forming new brain cells and connections and new functions for brain cells (neurons). Brain plasticity is adaptive – enhancing function, or compensation for lost function. The jury is now in that the brain is capable of remarkable widespread growth and adaptation throughout the lifespan – not just in childhood.

Brain plasticity comes into play whenever we form a new long-term memory, learn something new or develop a new skill, new neurons and new brain circuitry comes with it. With each new skill grows a new network of brain tissue. Cortical hemispheres change their circuitry with long term meditation practice. Focal points of cortex expand as you learn a new musical instrument.

Many neurologists feel that these extraordinary cases of hydrocephaly are a tribute to the brain's incredible plasticity. Does brain plasticity explain hydrocephaly?

In a sense brain plasticity is obviously at work here. Obviously these people’s brains have reorganized themselves massively – almost beyond recognition. But are the principles of this re-organization understood? The answer is no. While growing extra neural connection strengths or new neurons as a result of learning can be explained in terms of brain plasticity, the kind of colossal transformation we here goes far beyond what fits comfortably into standard scientific theories about brain function.

Patrick Wall, professor of anatomy at University College, London believes that talking as though these cases are explained by the brain’s plasticity “ is a cop-out to get around something you don't understand”. I’m with him.

Hydrocephaly and the power of the human mind.

In my view, hydrocephaly shows us that our MINDS can determine the neurobiology of our brains. By this I mean that these remarkable individuals with almost no brains are best understood by figuring out how mental causes cause and re-organize brain processes – rather than our usual way of thinking about it: that brain processes determine our mental life. The fact that these individuals with only a small fraction of the normal amount of brain tissue have normal or exceptional minds defies conventional neuroscientific explanations of behaviour. Getting an honors degree in mathematics with a 50 gram brain can only be explained if we accept that mental life in some important sense transcends our biological life: there must be emergent properties that are fully MENTAL which end up rewiring the brain in ways that defy our current scientific understanding.

Many of these individuals describe themselves as strong-willed and stubborn. I am going to propose a hypothesis: EVERY SINGLE ONE of these cases we have looked at has a strong mind. They are determined, stubborn, focused. If they took personality tests, these qualities would be revealed. They have minds that defy the odds. With a strong and determined mind, individuals with hydrocephaly prove that you only need a brain the weight of a large coin to get a first class honors degree in mathematics! Imagine what is possible with a strong mind and a 1.5kg brain like most of us have?


Roger Lewin, "Is Your Brain Really Necessary?" Science, 210, December, 1980, page 1232.

DOI: doi:10.1126/science.7434023

Persistent Link: http://dx.doi.org/10.1126/science.7434023

Author's Bio: 

Dr Mark Ashton Smith, is a cognitive neuroscientist, author and entrepreneur. Between 2000 and 2003 he was a Lecturer in the Department of Experimental Psychology at the University of Cambridge. His most recent position has been as Assistant Professor at Bilkent University, Turkey. His current research is in fluid intelligence and cognitive interventions. His business High IQ Pro, can be found here: http://www.highiqpro.com. His blog on fluid intelligence can be found here: http://www.fluidintelligence.org