[Early diagnosis of Alzheimer's disease: the prodromal and preclinical phase].

INTRODUCTION: Because Alzheimer's disease (AD) needs to be treated as soon as possible after onset, its early detection has become one of the core areas of research in the field of neurodegenerative diseases. DEVELOPMENT: Attempts to characterise the incipient phases of the disease have evolved from the appearance of the heterogeneous concept of mild cognitive impairment in the last twentieth century to the diagnostic criteria proposed for AD by current research. These criteria make it possible to perform an early diagnosis of AD (in the prodromal phase) that is at the same time aetiological, since it is backed up by objective biological markers which will be discussed in this work. Additionally, the article will also review the concept of preclinical AD, which is supported by evidence showing that the pathological process of AD begins years before the clinical manifestation of the disease.
CONCLUSIONS: To date, this preclinical phase is the one that has received less attention from researchers, although the development of complex imaging techniques with new tracers appears to be a promising beginning to the coveted path towards the preclinical diagnosis of the disease.