Muscular problem the old man has to fight against endlessly

• Partial paralysis
• Severe neurological problem
• A slight or partial paralysis
• Neurological problem

WordNet Word definitions in WordNet
n. a slight or partial paralysis

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Paresis \Par"e*sis\, n. [NL., from Gr. pa`resis, fr. parie`nai to let go; para` from + "ie`nai to send.] (Med.) Incomplete paralysis, affecting motion but not sensation.

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"partial paralysis," 1690s, Modern Latin, from Greek paresis "letting go, slackening of strength, paralysis," from stem of parienai "to let go," from para- (see para- (1)) + hienai "to send, throw" (see jet (v.)).

Wiktionary Word definitions in Wiktionary
n. 1 A paralysis which is incomplete or which occurs in isolated areas. 2 inflammation of the brain as a cause of dementia or paralysis.

Wikipedia Word definitions in Wikipedia
Paresis is a condition typified by a weakness of voluntary movement, or partial loss of voluntary movement or by impaired movement. When used without qualifiers, it usually refers to the limbs, but it can also be used to describe the muscles of the eyes ...