encephalopathy vs brain disease

encephalopathy and brain disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
encephalopathy	Yes	No	No	No
brain disease	Yes	No	No	No

As nouns, encephalopathy and brain disease are synonyms defined as:

Other synonyms of encephalopathy include brain disorder.

encephalopathy (noun)	brain disease (noun)
any disorder or disease of the brain	any disorder or disease of the brain