hydrocephalus

Borrowed from Ancient Greek ὑδροκέφαλον (hudroképhalon).

hydrocephalus (usually uncountable, plural hydrocephaluses or hydrocephali)

1. (medicine) A usually congenital condition in which an abnormal accumulation of fluid in the cerebral ventricles causes enlargement of the skull and compression of the brain, destroying much of the neural tissue.
   • 2025 January 25, Hanna Ziady, “‘Our innocent kids are struggling.’ Victims of massive listeriosis outbreak say those responsible must ‘do the right thing’”, in CNN‎^[1]:

     She was born with a condition known as hydrocephalus, which doctors said was caused by a listeriosis infection that her mother contracted while pregnant.

• water on the brain (informal)