From Quora: In 2007 in France, a 44-year-old man went to the doctor complaining of numbness in his leg and underwent a brain CT scan that revealed a shocking truth:
That man didn't have 90% of his brain. The skull was almost entirely filled with cerebrospinal fluid and all that remained of the brain was a thin peripheral portion surrounding the skull. You can plainly see this from the X-ray images below:
