shaking palsy vs brain disease

shaking palsy and brain disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
shaking palsy	Yes	No	No	No
brain disease	Yes	No	No	No

As nouns, brain disease is a hypernym of shaking palsy; that is, brain disease is a word with a broader meaning than shaking palsy:

shaking palsy: a degenerative disorder of the central nervous system characterized by tremor and impaired muscular coordination
brain disease: any disorder or disease of the brain

Other hypernyms of shaking palsy include degenerative disorder, brain disorder, encephalopathy.

shaking palsy (noun)	brain disease (noun)
a degenerative disorder of the central nervous system characterized by tremor and impaired muscular coordination	any disorder or disease of the brain