BBC - Future - Can you live a normal life with half a brain?:
Earlier this year, a case was reported of a woman who is missing her cerebellum,
a distinct structure found at the back of the brain. By some estimates
the human cerebellum contains half the brain cells you have. This isn't
just brain damage – the whole structure is absent. Yet this woman lives a
normal life; she graduated from school, got married and had a kid
following an uneventful pregnancy and birth. A pretty standard biography
for a 24-year-old.
The woman wasn't completely unaffected – she
had suffered from uncertain, clumsy, movements her whole life. But the
surprise is how she moves at all, missing a part of the brain that is so
fundamental it evolved with the first vertebrates. The sharks that swam when dinosaurs walked the Earth had cerebellums.