Neuroscience

[HenryTo]

Still in its infant stages:
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Boy missing cerebellum stymies medical experts

Three-year-old Chase Britton is a medical enigma. Born without a cerebellum, Chase is able to perform activities that have long been thought to be controlled by the cerebellum. Chase can walk, ride a bike, manipulate a pencil ... all of this upends conventional medical thinking. He "needs" a cerebellum to do these things, and he doesn't have one.
Chase's parents, Heather and David Britton, learned their son's cerebellum was missing when he underwent an MRI at age 1. "'He has the MRI of a vegetable,' one of the doctors said to us," Heather Britton said in an AOL news interview.

What is even more of a mystery is what happened to Chase's cerebellum. While he may have been born without it, it was visible in Heather Britton's sonogram pictures in considerable detail. So neurologists ponder not only how Chase functions without a cerebellum but also what happened to the cerebellum that was clearly present in utero. His technical diagnosis of cerebellar hypoplasia, normally indicating a small rather than an absent cerebellum, doesn't shed much light on the mystery. In Chase's case the cerebellum structure is absent and the space where it should be is filled with fluid.

Causes of Cerebellar Hypoplasia

According to Medline Plus, most brain malformations happen before a baby's birth. They can result from genetic conditions or exposures that thwart brain development such as excess radiation or infections.
With cerebrellar hypoplasia, the National Institutes of Health says, both congenital malformation syndromes and neurodegenerative disorders beginning in early childhood can play a role. That could shed some light on how Chase's cerebellum could be there before birth and gone by age one. But it doesn't begin to explain how Chase can do the things he does which one normally needs a cerebellum to do.

The Family That Walks on All Fours

VLDLR-associated cerebellar hypoplasia is one variant of the medical condition that is inherited and usually becomes obvious during infancy. VLDLR-associated cerebellar hypoplasia was the diagnosis of the Turkish family whose unusual quadripedal locomotion was the subject of a BBC documentary titled "The Family That Walks on All Fours" in 2006. At the time of the BBC documentary, scientists debated whether the Turkish siblings merely maintained infantile walking because the brain abnormality made bipedal locomotion difficult or perhaps lacked a crucial gene that facilitated the human transition to bipedalism.

Brain Reorganizes to Perform

A girl with a different part of her brain missing -- the cerebral cortex rather than the cerebellum -- may offer a clue to Chase's seemingly miraculous abilities. The girl identified only as AH was able to see perfectly despite having only half of her cerebral cortex, New Scientist reported in 2009. Normally, people missing half of their cerebral cortex would have only half of their visual field. But this child's brain circuits reorganized themselves, allowing her to see out of both the left and right visual fields. Brain scans confirmed that AH's retinal nerves, with no right cortex to connect to, established compensatory connections in the left side of her brain.