A TEENAGER who was born without the entire left hemisphere of her brain has above-average reading skills – despite missing the part of the brain that is typically specialised for language – 91av can exclusively reveal.
The 18-year-old also has an average-to-high IQ and plans to go to university. Brain scans reveal she has more of the type of brain tissue involved in reading than typical. Tests of her brain activity indicate that the right side of her brain has taken on some of the functions of the left, suggesting that the organ has adapted to compensate for the missing tissue.
The parents of the woman, known as C1, first noticed something was amiss when she was 7 months old. Most babies stop clutching their thumbs with their fist at around this age, but C1 continued to do so with her right hand. A brain scan at 10 months old revealed there was a sac of fluid where her left hemisphere should have been.
Advertisement
The woman has been diagnosed with hemi-hydranencephaly, an extremely rare condition in which a large part of the brain’s cortex is missing. Only nine cases have ever been reported.
C1 was enrolled in a research project when she was 14 months old. A team based at the University of Chicago followed her progress until she was 16 years old, along with that of 64 children with typical brains and 40 children who had experienced strokes in the weeks before or after birth. Their language, reading, spatial and maths skills were tested every four months until they were nearly 5 years old.
At first, C1’s language skills were below average compared with typically developing children of the same age, and her vocabulary was profoundly limited. But she improved over the years, and had average speaking skills by the time she was 4-and-a-half years old.
Her vocabulary and syntax improved, too. By the time she was almost 5, C1 had caught up with her peers. “In most of the tasks, she was within the normative average when she entered primary school,” says Salomi Asaridou at the University of Oxford, who has been studying her development.
C1 has excelled in other areas as well. When, between the ages of 5 and 7, researchers tested her ability to recognise and reorganise the sounds in words, C1 surpassed her peers. She was also exceptional at reading and was “in the superior range, and significantly better than our typically developing group”, says Asaridou.
What’s more, C1’s language skills don’t seem to have come at the expense of other cognitive skills, says Asaridou. As well as her IQ being in the average-to-high range for her age, she has typical spatial skills, and she is exceptionally good at short-term memory tests that involve recalling sequences of numbers.
Brain scans have revealed more about C1’s remarkable brain. When she was 14 years old, researchers used functional MRI to study her brain activity while she listened to stories. Asaridou and her colleagues compared C1’s results with those of 30 typically developing children who were between 12 and 14 years old.
“C1’s pattern of activity resembled what we saw in the left hemisphere of typically developing children,” says Asaridou. This adds to evidence that C1’s right hemisphere has adapted to take on some of the functions the left side usually handles, such as language processing.
A second set of scans, taken at the same age, revealed that C1’s brain has more white matter – the tissue that connects brain regions and allows them to communicate – than is typical. Specifically, she has more white matter in regions known to be involved in language skills, such as mapping sounds to articulation and reading, says Asaridou.
Rare case
C1 is rare among people with hemi-hydranencephaly, says Asaridou. Of the other known cases, only two of the six people tested have had no problems with language development. Asaridou thinks that a mixture of nature and nurture might have helped C1. Her family is affluent, so her parents could afford to provide her with speech and physical therapy from an early age. C1 has a younger brother who performs exceptionally in language tests, suggesting there might be a genetic factor to the siblings’ success, says Asaridou. “But this is all speculation. It’s a complicated case with a unique contribution of different factors.”
C1 does still experience some difficulties with moving the right side of her body. But she appears to be doing well in life generally and has successfully completed her exams.
Faraneh Vargha-Khadem at Great Ormond Street Hospital for Children in London says she isn’t surprised that C1 has developed sophisticated language skills. Every year, about 11 to 15 children with severe epilepsy have surgery at the hospital to remove an entire hemisphere of their brain, and they tend to recover well, demonstrating how remarkable the brain is, she says, “and how little we know about it”.
