((a)) For the purposes of this chapter, a person shall be considered to be permanently and totally disabled if such person is any of the following:
((1)) A patient in a nursing home for long-term care because of disability.
((2)) Disabled, as determined by the Commissioner of Social Security for purposes of any benefits administered by the Commissioner.
((3)) Unemployable as a result of disability reasonably certain to continue throughout the life of the person.
((4)) Suffering from—
((A)) any disability which is sufficient to render it impossible for the average person to follow a substantially gainful occupation, but only if it is reasonably certain that such disability will continue throughout the life of the person; or
((B)) any disease or disorder determined by the Secretary to be of such a nature or extent as to justify a determination that persons suffering therefrom are permanently and totally disabled.
((b)) For the purposes of this chapter, a person shall be considered to be in need of regular aid and attendance if such person is (1) a patient in a nursing home or (2) blind, or so nearly blind or significantly disabled as to need or require the regular aid and attendance of another person.
((c)) For the purposes of this chapter, the requirement of “permanently housebound” will be considered to have been met when the veteran is substantially confined to such veteran’s house (ward or clinical areas, if institutionalized) or immediate premises due to a disability or disabilities which it is reasonably certain will remain throughout such veteran’s lifetime.