Dec 23 2016

Man Living with 10% of His Brain?

hydrocephalus2Here is the title of a science new story from July 2016: A man who lives without 90% of his brain is challenging our concept of ‘consciousness’. This is an excellent example of horrible science news reporting. It is a cautionary tale of what can happen when a reporter does not adequately vet their story with actual experts.

These are the images from the original paper, which was published in 2007. They are quite impressive and I can see how a lay person might misinterpret them. I can see how a journalist might make assumptions about what they are seeing, and not even know enough to question those assumptions and therefore never asked the experts they interviewed the right questions.

In fact the journalist, Fiona MacDonald, got off on an irrelevant tangent about consciousness, even though this case reports has not implications for our understanding of the neurological basis of consciousness.

I was recently reminded of this case, and the bad reporting surrounding it, by a comment left on a previous blog of mine in which the commenter notes:

Furthermore the author noted, rightly that if a model of externalized consciousness was to be tested, we would have to look for anomalies, cases where the brain does not explain the mind. There has been a case recently where a man who retained only 10% of his brain by mass was found to function semi normally with an IQ of 75, a job, a wife and two kids.

So he was offering this case report as an anomaly which calls into question our model of consciousness.

What is really going on here is quite different. The subject developed hydrocephalus at age 6 months. The brain normally has fluid-filled cavities within it, called ventricles. They are filled with cerebrospinal fluid (CSF), a clear liquid that is mostly water. CSF is produced by the choroid plexus and the lining of the ventricles, at a rate of about 500ml per day. The CSF flows through the ventricles, then through openings which carry it outside the brain and around the spinal cord. CSF is ultimately absorbed by the arachnoid granulations and perhaps also by lymphatic channels.

There are two types of hydrocephalus, communicating and non-communicating. Communicating hydrocephalus occurs with all the passageways for CSF open, and result from either over production or, more commonly, atrophy (shrinkage) of the brain. This the case of atrophy the CSF is just filling in the available space. Non-communicating hydrocephalus occurs when there is a blockage to the passage of CSF, causing it to backup, increasing pressure within the ventricles.

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.

The most impressive case I have personally seen was a patient who had a benign and slow growing tumor in the front of his skull. This essentially filled the front half of his brain cavity, squishing the brain into the back half. As a result he had frontal lobe dysfunction, which clinically looked like schizophrenia, and amazingly otherwise had very few neurological deficits on exam. In fact he was misdiagnosed with schizophrenia for 20 years (in fairness he was lost to medical follow up for this entire time). When he finally presented for evaluation we found the tumor, which the surgeons removed. Over the next week his brain slowly re-expanded to fill the now vacant skull, and he returned to fairly normal functioning.

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.

To put his function into perspective, and IQ of 75 is considered borderline functional. A person with that IQ can typically go about their normal day-to-day life, even get married, have children, and hold down a job. But they will have profound intellectual limitations. They will likely be untrainable beyond the simplest tasks, may not be able to make change, would be challenged by complex electronics or other appliances, and would have poor problem solving. Obviously one number does not capture all the variability present, but this is a basic picture of typical functioning at that level.

It is important to note that this level of impairment is in proportion to the physical brain damage caused by the chronic hydrocephalus. There is no mystery here, no challenge to the neuroscientific paradigm of cognitive function. This case does not challenge the notion that consciousness is a brain function.

Conclusion

This case is, as I noted above, a good example of an interesting scientific story that is horribly mangled by a reporter who simply did not understand what was really going on and failed to properly put the story together. It is possible that she did not really even try – often journalists will think they see a good angle, a “hook” to sell the story, and they tell that story, regardless of what the experts they interview tell them.

I have had this experience many times – talking to a reporter who is not researching something to figure out what the story is. Rather, they already have the story and now they are just backfilling quotes from experts (or people they can present as experts). They don’t want to hear that they have the story wrong.

The end result is that the take-home message that the public reads is simply wrong, and may have nothing to do with the actual science. It is also clear from research, and from copious experience, that most people do not read much beyond the headline or perhaps the one-line blurb beneath the headline. It is amazing to me how many times people will link to the reporting of a study, or even directly to a study, to support their position when they clearly did not read the article they are linking to, because it does not support their position.

I know everyone does not have the time or background to read and comprehend the primary literature and put it into perspective. That’s fine. But then don’t think you have an informed position because you can link to a secondary source based entirely on the headline.

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