Doctors surgically removed the part of a little boy’s brain that powers sight on his left side – yet he can still, because his brain reprogrammed itself to fill in the gaps, according to a Carnegie Mellon University new case study.
The brain’s ability to repair itself and compensate functionally when it is damaged is astounding, and extreme and rare procedures like the boy’s lobectomy give scientists a unique chance to learn about – and be amazed by – its flexibility.
From the time he was four, the little boy, known only as ‘UD,’ started having seizures caused by a minor brain tumor.
His family and doctors tried all manner of medications and treatments to stop his epilepsy from disrupting the young boy’s life, but nothing worked.
After nearly three years of failed attempts to curb his seizures, they were ready to try something much more drastic.
As time has gone on since he had much of the right side of his brain removed, doctors have watched in amazement as the left side of the now 11-year-old-boy has taken over visual functions such as seeing faces (pink) and recognizing patterns and objects (green and blue)
Just before his seventh birthday, doctors a surgically removed a large portion of the boy’s brain where abnormal electrical activity kept cropping up and causing him to have seizures.
They took out about one third of the right hemisphere of his brain in a procedure that eliminated the epileptic episodes but essentially took the left side of his vision offline.
Our vision is wired counterintuitively. The left side of the brain process what the right eye sees and visa versa.
So when UD’s entire right occipital lobe – the portion responsible for making sense of visual information – disappeared, so did the left side of the world, as far as he could see.
His doctors knew the risks, but they did not know how his brain would change and compensate to fill in the literal blanks left by the operation.
Lobectomies are extreme and rare but highly effective treatments for epilepsy.
Somewhere between four and six percent of patients with treatment-resistant epilepsy undergo the surgery, but for as many as 70 percent of children who do, a lobectomy is a lifelong cure.
Because it is so rare, and does not always involve removing the same regions of the brain, the exact prognosis after the procedure holds some of the same mysteries for doctors and patients alike.
Lobectomies are considered extremely safe, and complications are rare.
For patients, the smaller uncertainties of life after the procedure are preferable to the daunting certainty of a lifetime of seizures.
For doctors, these patients are a rare opportunity to learn about the brain and its plasticity, or ability to change in order to optimize cognitive performance and compensate for losses.
Incredibly, the left side of UD’s brain picked up the slack and allowed his vision to remain almost entirely intact.
His brain rewired itself so that parts of the left side of his brain are now dedicated to processing information that the now missing right side would normally have handled.
He is able to see and track patterns and recognize faces and objects clearly.
‘The only deficit is that he could not see the entire visual field – when he is looking forward, visual information falling on the left side of the input is not processed – but he could compensate for this by turning his head or moving his eyes,’ says Dr Marlene Behrmann, a neuroscientist and co-author of the case study said.
While that may sound like a fairly significant deficit, UD leads a remarkably normal life.
In fact UD, who had always been smart and academically successful still has the above average IQ that he did before his surgery and he gets grades that are anywhere from proficient to good in school.
Most importantly, the boy is seizure free.
He is now 11, and the only major differences between him and his peers is that he goes to vision therapy during the school day and sits on the left side of the class room so that the blank part of his vision – corresponding to his left eye – is directed to the edges of the room and he see more of his surroundings better.
‘While we know the human brain has incredible potential to reorganize and remap, it seems that humans still require two intact and functional hemispheres to have a full 180 degrees of peripheral vision without having to move our eyes or turn our heads to avoid blind spots,’ Dr Behrmann says.
‘Our results indicate dynamic reorganization over time in higher-order functions, but not the lower-order visual cortex.’
In other words, UD’s brain was able to prioritize complex processing of visual information from as much of his field of view as possible, but couldn’t ultimately ‘restore’ full vision to the left eye.
Armed with this new understanding, Dr Behrmann and her team say that their findings ‘shed light on the visual system of the cortex and can potentially help neurologists and surgeons understand the kind of changes that are possible in the brain.’