From mild cognitive impairment to prodromal Alzheimer disease: A nosological evolution

Despite of the positive medical and scientific advances generated through the mild cognitive impairment (MCI) diagnosis, as we will see along this paper, the concept of MCI presents several major limitations. MCI defines a syndrome and therefore it may be the consequence of different diseases with distinct aetiologies. Furthermore, the philosophy behind the MCI scenario has been to detect a group of symptoms that eventually will evolve into a distinct disease. In contrast, our nowadays aim is to detect a disease in its earlier stages that eventually will evolve from one clinical syndrome to another. As an example, our aim now is to detect early AD that initially will manifest as a memory syndrome and eventually will evolve into a dementia syndrome. Consequently, in order to overcome the syndromical diagnosis behind MCI, the concept of prodromal AD (Prd-AD) has recently emerged. Prd-AD is defined as the symptomatic predementia phase of AD, generally included in the MCI category; this stage is characterised by symptoms not severe enough to meet currently accepted diagnostic criteria for AD. Being a nosological concept, it has several potential advantages related with early diagnosis and treatment, together with the possibility to contribute to the development of disease modifying drugs.