Cognition is compromised in many neurological conditions; often it is impossible to anticipate the onset of cognitive impairment. The timing and the extent of that impairment may be elusive, and the patient may worry that decisions regarding care will be made by individuals who have no awareness of his personality or priorities.

The patient may wish to designate a particular individual who is to be trusted to make decisions or give consent on the patient's behalf for medical or surgical treatments. Who is to take that responsibility? In some countries an individual patient can, while competent, formally appoint, by a duly witnessed, legally binding document, another person to be a medical advocate, a guardian and a surrogate decision-maker.

Where legislation to authorize the appointment of a proxy decision-maker is not in place, it may be possible to ensure that, during the earlier stages of an illness when cognition remains close to normal, matters of future directions are raised in ways that allow family members to feel confident about the patient's fears and hopes, and to know what are the patient's directions and wishes, in future times of potential difficulty. In such a case, a clear and agreed understanding among family members about ‘what Mother said she wanted’ can be very helpful, and guide compassionate medical care in the terminal stage. It may be taken into account if a legal judgment becomes necessary.