The following definition is recommended:
"Permanently and totally disabled" means that the individual has some permanent physical or mental impairment, disease, or loss, or combination thereof, this substantially precludes him from engaging in useful occupations within his competence, such as holding a job.
Under this definition:
"Permanently" refers to a condition which is not likely to improve or which will continue throughout the lifetime of the individual; it may be a condition which is not likely to respond to any known therapeutic procedures, or a condition which is likely to remain static or to become worse unless certain therapeutic measures are carried out, where treatment is unavailable, inadvisable, or is refused by the individual on a reasonable basis; "permanently" does not rule out the possibility of vocational rehabilitation or even possible recovery in light of future medical advances or changed prognosis; in this sense the term refers to a condition which continues indefinitely, as distinct from one which is temporary or transient;
"Totally" involves considerations in addition to those verified through the medical findings, such as age, training, skills, and work experience, and the probable functioning of the individual in his particular situation in light of his impairment; an individual's disability would usually be tested in relation to ability to engage in remunerative employment; the ability to keep house or to care for others would be the appropriate test for (and only for) individuals, such as housewives, who were engaged in this occupation prior to the disability and do not have a history of gainful employment; eligibility may continue, even after a period of rehabilitation and readjustment, if the individual's work capacity is still very considerably limited (in comparison with that of a normal person) in terms of such factors as the speed with which he can work, the amount he can produce in a given period of time, and the number of hours he is able to work.
45 C.F.R. §233.80