When a woman checked herself into the PLA General Hospital in China's Shandong Province, she reported symptoms of dizziness and nausea. She’d had a shaky walk for most of her life, and unlike most people, who learn to walk when they’re very young infants, she was only able to master this skill at seven years old. She was also only able to speak properly from the age of six.
According to Helen Thomson at New Scientist, once the doctors performed a CAT scan - which combines information from several X-rays to produce a comprehensive image of structures inside the brain - the source problem was immediately made clear. The woman’s entire cerebellum was missing, and in its place was nothing but cerebrospinal fluid, which is a special substance that protects the brain from damaging knocks and disease.
The cerebellum makes up 10 percent of the brain’s total volume, but contains 50 percent of its neurons. It sits beneath the brain’s two hemispheres, and is made up of a unique combination of small and compact tissue folds. It plays a crucial role in motor control and speech, and there’s evidence to suggest that it’s involved in cognitive functions such as attention and language, and perhaps even in mitigating feelings of fear and pleasure.
While this woman is not the first person born without a cerebellum, she is just one of nine people known to have survived to adulthood without it. "A detailed description of how the disorder affects a living adult is almost non-existent, say doctors from the Chinese hospital, because most people with the condition die at a young age and the problem is only discovered on autopsy,” says Thomson at New Scientist.
The fact that the woman has so far displayed only relatively minor reactions to the missing part of her brain suggests how ‘plastic’ and adaptable this organ is, and perhaps her brain’s cortex has been filling in the gaps in order for her to function.
"These rare cases are interesting to understand how the brain circuitry works and compensates for missing parts," Mario Manto, an expert in cerebellar disorders at the Free University of Brussels in Belgium, told New Scientist.