Handwriting analysis to support neurodegenerative diseases diagnosis: A review

Neurodegenerative diseases (NDs) affect millions of people worldwide, with Alzheimer's and Parkinson's being the most common ones, and it is expected that their incidence will dramatically increase in the next few decades. Unfortunately, these diseases cannot be cured, but an early diagnosis can help to better manage their symptoms and their evolution. These aspects explain the importance of developing support systems for the early diagnosis of neurodegenarative diseases. Handwriting is one of the abilities that is affected by NDs. For this reason, researchers have also investigated the possibility of using the handwriting alterations caused by NDs as diagnostic signs. This paper presents a review of the literature of handwriting analysis for supporting the diagnosis of Alzheimer's and Parkinson's disease as well as of mild cognitive impairments (MCI), with the goal of providing interested researchers with the state-of-the-art research. Moreover, with the aim of providing some guidelines on the features to use for representing handwriting and the writing tasks patients should perform, we also review some widely used approaches for modeling handwriting. Finally, open issues are also discussed to identify promising areas for future research.