There is a case of a woman born without a cerebellum, and the neocortex was able to compensate. Her movement was less smooth than most peoples, but close enough

There is a case of a woman born without a cerebellum, and the neocortex was able to compensate. Her movement was less smooth than most peoples, but close enough to “normal” that she didn’t discover her cerebellum was missing until well into adulthood when she had a brain scan for an unrelated reason.