So his brain’s just squished (rather than only 10% there): A Bonsai Brain

Estimated read time (minus contemplative pauses): 8 min.

hydrocephalus of the "man with only 10% of brain"
90% gone, or just compressed?

I occasionally run into the story of a French civil servant with non-communicating hydrocephalus whose brain’s been 90% eaten away by cerebrospinal fluid over a period of 30 years. The idea is that, because it happened slowly, his brain’s plasticity allowed for passable cognitive function—he has an IQ of 75—to be taken up by the spared 10%.

After first hearing about this, I assumed all the requisite architecture of a fully functioning, 100%-intact brain must be in place, though uniquely organized. And it seemed neuroscientists and consciousness researchers would be all over this case if the man actually had a radically restructured brain—for example, was missing a hippocampus while still encoding long-term memories. But I’d never encountered mention of it by serious researchers. So why the reports of his brain being 90% gone? Today I decided to dig around a little to answer that question.

I also wanted to learn more about the possibility of what I call “bonsai brain,” in which a brain’s shape is gently massaged, over many years, with some aesthetic or otherwise meaningful end in mind. This could be initiated by parents during infancy, or maybe would be best started as a (self-individuating) teen, after synaptic pruning. Imagine that culture.

One might also think there’s some cognitive, or even emotional, benefit to arranging certain parts of the brain in certain physical relations to one another (which reminds me of one of the reasons Wikipedia cites for the practice of head binding: “pseudoscientific ideas about the brain’s ability to hold certain types of thought depending on its shape”; but my idea’s not so pseudoscientific, right? Right? I mean, you could make yourself into a synesthete if you do it right.)

Back to the 10%-of-his-brain Frenchman.

Relevant first-page Google hits—mingled with articles busting the myth that we humans only use 10% of our brains—seem to say more or less the same stuff: normally functioning man with only 10% of brain stumps scientists. For example, Science Alert‘s 2016 article (by Fiona MacDonald) titled “Meet The Man Who Lives Normally With Damage to 90% of His Brain,” states that the case is “causing scientists to rethink what it is from a biological perspective that makes us conscious.” That article extensively cites a Quartz article (by Olivia Goldhill) that came out 12 days earlier called “A civil servant missing most of his brain challenges our most basic theories of consciousness.”

The Quartz article says that “doctors believe the man’s brain slowly eroded over 30 years due to a build up of fluid in the brain’s ventricles, a condition known as ‘hydrocephalus.'” It quotes cognitive scientist Alex Cleeremans: “Any theory of consciousness has to be able to explain why a person like that, who’s missing 90% of his neurons, still exhibits normal behavior.” I presume Quartz got in touch with Cleeremans to ask about the case, as, from what I could find, it’s not something he’s discussed elsewhere.

Aside from Cleermans, I don’t see any evidence of doctors being flummoxed or otherwise bowled over by this case. And the Science Alert article has a January 2017 note at the end stating that the man’s brain may not be eaten away after all, but rather was compressed by his condition.

Digging a little more, I found a Wired write-up from 2007 (by Brandon Keim) called “Brain Not Necessary for French Civil Service Worker,” which quotes Reuters: “Their shocking discovery: his lateral ventricles—the little chambers of brain-cushioning cerebrospinal fluid—were monstrously oversized. His head was full of water; his brain amounted to, as Reuters described, “little more than a sheet of actual brain tissue.” The cited Reuters article, called “Tiny brain no obstacle to French civil servant,” also refers to the man as having “an unusually tiny brain,” and notes that the researchers who scanned the man’s brain were “astonished.” It also includes a quote about brain plasticity from a doctor they themselves presumably contacted for comment. There’s no mention at Wired or Reuters of the man having only 10% of his brain, though, Wired‘s title does sorta suggest he has no brain, by saying he doesn’t need one.

Where did that 10% number come from? Was it an eyeball estimate some journalist made, looking at the brain scan, somewhere along the line in this journalistic telephone game? And where are the reports from these allegedly “astonished” researchers? Reuters quotes one of the researchers on the project, Dr. Lionel Feuillet, from a letter he wrote to Lancet, the journal that published the original article (more about which below), but that quote just mentions that the man was a married father of two and a civil servant.

I don’t have access to that physical journal, but I might be able to get ahold of it later at a university library. In the meanwhile, the article itself is available online at the Lancet website: Brain of a white-collar worker1. It’s one paragraph long with four photographs (see the top of this post), and, again, makes no mention of the man having only 10% of his brain; nor is there even anything about brain damage. In fact, the authors refer to “normal nuerological development.” Indeed, from what I can gather it’s the lack of brain damage that makes the case interesting. The only thing report says about the man’s brain, pathology-wise, is: “CT showed severe dilatation of the lateral ventricles (figure); MRI revealed massive enlargement of the lateral, third, and fourth ventricles, a very thin cortical mantle and a posterior fossa cyst.” Finally, the tone is as dry as you’d expect, rather than one of astonishment.

So, I dug a little more and found a smart-sounding 2007 article (by Louis Buckley) called “The man with a hole in his brain” at Nature‘s website (dated one day before the Lancet publication date), in which it’s pointed out that “an accumulation of fluid in the ventricles and an enlargement of the skull due to the great volume of fluid pressing against it… had squeezed his brain into a narrow layer around the outside of the fluid, doctors report in the Lancet today.” Nature also quotes Dr. Feuillet:

“We were very surprised when we looked for the first time the CT scan,” says Lionel Feuillet, a neurologist at the Mediterranean University, Marseille. “The brain was very, very much smaller than normal.” … The fact that his medical record shows normal neurological development is remarkable, says Feuillet. “This case is unique to our knowledge. We have never encountered such severe hydrocephalus before.”

Ah. This supports the idea that the researchers were surprised. It would be great to know what’s meant by “smaller”: does a sponge get smaller when you squeeze it? In a certain way it does, but it still has all the same parts it has when squeezed and dried as it does when soggy and bloated.

I could keep digging around, but I think I’ll leave off with a more recent debunking article, this one by Steven Novella at the Neurologica blog. He starts out by referring to the aforementioned Science Alert article as “an excellent example of horrible science news reporting” (I assume it was Novella’s article that prompted the January 2017 disclaimer about the man’s brain perhaps being compressed rather than damaged). Novella goes on to write:

When non-communicating hydrocephalus is acute it is very symptomatic and dangerous. It causes severe headaches and brain damage, and can even be fatal. When it is chronic, however, (and this is critical to understanding this case) it is far less dangerous and symptomatic. If the pressure slowly builds up then the brain will slowly compress under that pressure. The brain is like jelly, and can be impressively compressed while still maintaining its function. …

In this case of hydrocephalus, the patient was treated with the standard intervention, a shunt to remove excess fluid and reduce pressure. At age 14 he presented with poor balance and leg weakness. His shunt was not working properly. It was revised and his symptoms resolved. At the time of the case publication the patient was 44. He was again presenting with leg weakness, and again needed additional shunting which resolved the weakness.

However, the patient was found to have an IQ of 75, which is almost certainly a consequence of his chronic hydrocephalus. The images above are impressive, but perhaps more impressive is that his brain is mostly all still there, just pressed into a thin cortical rim. He did not lose 90% of his brain mass, as the commenter falsely assumed. There has probably been some atrophy over the years due to the chronic pressure, but not much.

Between Novella’s article, the Nature article, and the actual case report, it seems to me that what’s impressive in this case is just how compressed the man’s brain is without incurring significant damage, rather than anything to do with getting along as a relatively normal, walking and talking conscious guy with 90% less brain tissue than he would have had otherwise. That’s not how it’s presented in many of the articles. Notice the difference between “missing 90% of his brain due to damage” and “having a fully functioning brain—with all the requisite architecture for consciousness and working at least in the ballpark of normal cognitive function—despite have only 10% of the brain tissue as found in a typical adult male brain.”

I mean, the man clearly has 100% of his the brain he has. So some more precise explanation is owed by those who say he’s missing 90% of his brain.

It seems a third—less newsworthy though still interesting—option is now on the table: He has roughly the expected amount of tissue (with some deterioration), but it’s all squished up, like when you suck the air out of a clothing storage bag. Or, as in a tumor case Novella describes as the most impressive squished brain case he has personally seen: “Over the next week [after removing the tumor] his brain slowly re-expanded to fill the now vacant skull, and he returned to fairly normal functioning.”

Maybe the same could happen for the French civil servant. And maybe this all spells hope for my bonsai brain. I’d like mine to be Mandelbrot-set–shaped. Or maybe skull-shaped. Or maybe like an octopus in a pretzel pose. That’d be cool.

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Further Reading


  1. Volume 370, No. 9583, p262, 21 July 2007, authors: Dr Lionel Feuillet, MD; Henry Dufour, PhD; Jean Pelletier, PhD

3 Replies to “So his brain’s just squished (rather than only 10% there): A Bonsai Brain”

  1. When I hear “we only use 10% of our brains!”, I think of a tree canopy with leaves that grow only on the branch tips. The canopy looks voluminous, but only the surface layer of each branch is doing real work. The rest of the canopy (the inside) is simply a support system of transmitting cables. In this analogy, most of our brain volume is made of the “cables”, not processors. With this analogy in mind, 10% by volume or mass sounds about right to me—not at all shocking or mysterious.

  2. The more likely scenario here is that he really is missing that much of his brain. Typically you don’t just randomly get non communicating hydrocephalus… rather something happens to cause it. Hydrocephalus, while descriptive, is a symptom rather than an original cause. For instance, in cases where a person has extremely enlarged ventricles, there is usually something blocking the normal flow of cerebral spinal fluid in those ventricles. Having an intraventricular hemorrhage would cause such an issue, as the resultant blood products can block flow. Once that flow is blocked, fluid builds up and causes ‘hydrocephalus’. If/when more fluid builds up the person starts having issues as it presses up against brain matter. At that point the person needs a shunt to help drain fluid. If the fluid isn’t drained it doesn’t simply compress the brain, it actually will expand the skull and/or as it creates more pressure against the brain matter becomes damaged, and in the brain damage begets more damage. I would recommend looking up encephalomalacia. This guy likely has porencephaly (where damaged brain became soft and eroded into a fluid filled cyst – the empty areas you see are fluid), but not because the brain is compressed, because the brain in those areas became soft and essentially dissolved.

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