This type of coverage is sometimes referred as serious illness insurance is a supplemental medical insurance to provide a substantial (one-time) lump-sum cash benefit for a listed critical illness (illnesses that may result from injury as well as disease and include specified major surgery.)
Maximum benefit is paid only once for a specific illness that is explicitly defined in the policy, and typically the maximum benefit is paid for Alzheimer's, blindness, life-threatening cancer, deafness, heart attack, major organ transplant, paralysis, multiple sclerosis, stroke, renal failure.