A Comparative Analysis of the Treatment of Decision-Making by or for Patients with Neurodegenerative Diseases in Four Legal Jurisdictions.

Dementia is associated with the gradual impairment of mental ability. The population of people suffering from dementia is as large as 50 million. Most dementia cases result from various neurodegenerative diseases (NDs) linked by a progressive degeneration of neurons. Among NDs, Alzheimer's disease (AD) is the most frequent cause of dementia and accounts for 60- 80% of cases. Certain pathological changes on the cellular and subcellular level occur even 15 years before the manifestation of clinical symptoms of AD. This first asymptomatic phase of AD is considered a preclinical stage, whereas mild cognitive impairment (MCI) is the symptomatic pre-dementia stage. The third, fully symptomatic phase of AD is dementia due to AD. The presence of specific proteins in the cerebrospinal fluid (CSF) may be considered as a characteristic feature of some NDs. The measurement of their CSF concentrations, together with neuropsychological examination and neuroimaging, may be useful for diagnosing AD. The collection of CSF samples is performed by lumbar puncture, which is a medical procedure that requires obtaining informed consent from patients. While asymptomatic AD patients have full legal capacity, those with dementia require a legal guardian who will represent them. Thus, the objective of this study is to compare the legal systems regulating the legal capacity issue in the USA, U.K. (England and Wales), Germany, and Poland. These countries have been chosen as examples of three different types of legal orders, according to the sources of law, i.e., civil law, common law, and case law.