Hydrocephalus, also known as "big fat head syndrome," is a condition in which water fills the skull cavity and expands it, so that it resembles a helium balloon or a grey alien head. Sufferers of hydrocephaly often lose balance as their brains swim in an over-expanding thick liquid, causing them to weave and bob like bobble-head dolls. These most unfortunate sufferers commonly believe they have developed super-powers of brilliance and suavity, as their heads continue to swell.