Surrogate decision-making for people with congenital or acquired incapacity of judgement in the absence of known preferences: a scoping review

Background: Medical decision-making for individuals lacking the capacity to consent often involves ethically and emotionally challenging deliberations, how to make appropriate surrogate decisions in acute settings, and how to plan in advance. This is particularly true for two patient populations: (1) adults who have lost their decision-making capacity and whose presumed wishes are unknown, and (2) individuals with congenital incapacity due to lifelong cognitive impairments. This study aimed to critically synthesize the existing literature on surrogate decision-making and advance care planning (ACP) for these populations, as there are currently no detailed national guidelines for navigating such complex situations. Methods: A scoping review was conducted in accordance with PRISMA-ScR guidelines. Four databases (PubMed, Scopus, Web of Science, and Google Scholar) were searched. Eligible articles included those published in English or German since 2010 that addressed decision-making and documentation for adults lacking judgement capacity and whose preferences are unknown. Results: 15 relevant publications were included. These addressed key concepts such as the best interest standard, substituted decision-making and quality of life, and reflected on the use of tools like Patient Preference Predictors. However, none offered detailed guidance on how to implement surrogate decision-making or ACP in practice for cognitively impaired individuals. Conclusion: Surrogate decision-making for individuals without known preferences or a living will remains insufficiently structured and ethically ambiguous. While the need for national guidelines is widely recognized, existing frameworks fail to translate ethical principles into practical, actionable steps. The development of detailed, transparent, and ethically grounded guidelines is urgently required to support decision-making in clinical practice. Supplementary information: The online version contains supplementary material available at 10.1186/s12910-025-01276-4.