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 – New
Scientist 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 C
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.
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 withtypically 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 developinggroup”, 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
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”. ❚10 | New Scientist | 15 February 2020
“ The teenager has hemi-
hydranencephaly. Only
nine cases of this condition
have ever been reported”News
MARK ALBERHASKY/RGB VENTURES/ALAMYA child with the rare condition
of hemi-hydranencephalyNeuroscienceJessica HamzelouTeenager excels with half a brain
18-year-old with extremely rare brain condition has above-average reading skills