At a threshold: making decisions when you don't have all the answers.

Many people who sustain a brain injury also lose decisional capacity. They need someone who will be a partner with clinicians in making decisions on their behalf. This article reviews ethical aspects of decision making; the legal foundation in the United States for surrogate decision making; the experience of surrogate decision making on behalf of people who have a brain injury, including similarities and differences between such decision making for the dying and for those who have a brain injury; and ways to approach intractable disagreements between surrogate or family and clinicians. It provides guidelines for clinicians and surrogates and suggests topics for research. Two people who have suffered a brain injury and the spouse of one are coauthors.