recur – v. to happen or appear again

retain – v. to continue to hold (something, such as heat or moisture) as time passes

paralysis – n. medical : a condition in which you are unable to move or feel all or part of your body

poliomyelitis – medical n. : polio

chemotherapy – medical n. : the use of chemicals to treat or control a disease (such as cancer)

modify – v. to change some parts of (something) while not changing other parts