writer's cramp vs muscle spasm

writer's cramp and muscle spasm both are nouns.

Word	Noun	Adjective	Verb	Adverb
writer's cramp	Yes	No	No	No
muscle spasm	Yes	No	No	No

As nouns, muscle spasm is a hypernym of writer's cramp; that is, muscle spasm is a word with a broader meaning than writer's cramp:

writer's cramp: muscular spasms of thumb and forefinger while writing with a pen or pencil
muscle spasm: a painful and involuntary muscular contraction

Other hypernyms of writer's cramp include cramp, spasm.

writer's cramp (noun)	muscle spasm (noun)
muscular spasms of thumb and forefinger while writing with a pen or pencil	a painful and involuntary muscular contraction