Kinematic features of the handwriting process are promising for discriminating patients probably affected by neurodegenerative disorders from healthy controls and potentially for identifying the stage of the illness. Many tasks have been proposed and tested, however the scientific community still lacks a complete protocol able to collect different traits useful to the research community and at the same time to be of real use for doctors in their daily activities. This paper collects all the different tasks already applied and proposes a protocol for handwritten traits acquisition to be integrated into standardized cognitive and functional tests already accepted, tested and used by the medical community working on the assessment of neurodegenerative diseases.
Neurodegenerative disorders, such as Alzheimer’s disease (AD) [
2. Monitoring and tracking of its progression; 3. The diagnostic differentiation of the disease with respect to similar disorders.
Recently, a growing research interest has arisen towards the possibility to
automatically discriminate between impaired subjects and healthy controls on the basis of
kinematic features obtained through simple and easy-to-perform handwriting tasks, e.g. [
However, although encouraging results have been obtained, there are several open
issues that demand further research [
To address these issues, the present paper aims to propose a suitable protocol for handwriting data acquisition. It is important to note that, since a handwriting-based decision support system is not expected to replace standard techniques, but to strengthen them by providing precise and quantitative measurements, the proposal here presented is designed to integrate standardized cognitive and functional tests (already accepted, tested and used by the medical community). To this end, the protocol focuses on: • Handwriting tasks for the extraction of kinematic features; • Standard routine tests that are suitable to be carried out in a digitized way.
The rest of the paper is structured as follows. Section 2 concerns a literary review that focuses on the most employed handwriting tasks for clinical assessment. Section 3 advances our proposal which takes into account both standard and handwriting tasks. Section 4 concludes the paper and sketches future developments of our research. 2
Among the various methodological approaches, those related to Alzheimer’s disease and Parkinson’s disease have been considered: being the two most widespread neurodegenerative disorders, they have been the most widely investigated by researchers.
As mentioned above, writing is a skill that involves a complex feedback system and
implicates the participation of several cognitive processes. For this reason, most of the
works in literature focus on tasks such as the Archimedes spiral, single letters or simple
words/sentences writing in order to investigate purely motor aspects of handwriting.
These tasks have been extensively used in studies based on static features of
handwriting and significant differences between impaired subjects and healthy controls, based
on these features, have been revealed [
Similar findings have also been reported in papers focusing on the kinematic features
of the handwriting process. The Archimedes spiral is probably the most popular
handwriting exercise. Spiral, as well as circle drawing, in fact, have been frequently used
for the evaluation of the motor performance in various movement disorders, including
AD and PD, e.g. [
Words containing one or more repetitions of the cursive letters “l” and “e” are the
second-most common exercises in handwriting assessment, e.g. [
In addition to these tasks, writing simple words and short sentences have also been
widely adopted, e.g. [
In [
Finally, in [
The goal of this paper is to propose a digitized protocol for the early assessment of neurodegenerative disorders, including handwriting tasks for a subsequent extraction and analysis of kinematic features of the handwriting process. The protocol is made up of three parts: an initial screening; a battery of a digitized version of standard cognitive and functional tests; finally, some of the most relevant handwriting tasks already reported in the literature. The first two parts mostly require the examiner to provide a data entry; the last one requires the patient to perform the tasks. An overall model of the protocol is depicted in Fig. 1.
It is worth noting that the proposal is conceived to be deployed on inexpensive and commercially available digitizing tablets. Typically, these tablets are able to capture not only temporal and spatial variables of handwriting, but also the pressure exerted over the writing surface, the azimuth, i.e. the angle of the pen in the horizontal plane, the altitude, i.e. the angle of the pen with respect to the vertical axis, and so on. Moreover, these devices can capture pen movement not only while the pen is on the writing surface, but also when the pen is in close proximity of the surface, i.e. in-air.
In the following, the three parts are described. 3.1
The first part consists in a simple screening routine allowing the examiner to collect personal and clinical information of the patient. In addition to general questions, the family history of the patient and the presence of risk factors, such as diabetes, hypertension, obesity, etc., can be evaluated. Caregivers are then asked to answer questions about the most common symptoms of dementia. The interview is mainly concerned with memory deficit. If at least one question is answered positively, the protocol continues; otherwise, it ends. In the former case, the patient is asked to provide his/her signature as first handwritten trait captured by the device. The signature is acquired both in this initial stage and at the end of the second stage, as signature may vary depending on the emotional state of the signer.
General information
Common symptoms of dementia? yes Signature Mini-Cog Suspected dementia? yes IADL scale/
MMSE/ Additional tasks
Signature no no
Handwriting tasks
A standard assessment typically includes cognitive and functional tests. The tests
suitable to be carried out in a digitized way included in our proposal are: Mini-Cog [
Mini-Cog is a short screening test, as it lasts no more than 3 minutes. The test is composed of two parts: a 3-item recall test and a simple clock drawing test. The score is calculated as follows: 1 point for each word recalled without cues, and 2 points for a normal clock drawing. A total score of 3, 4 or 5 indicates lower likelihood of dementia. One may proceed with the administration of the following tests only after obtaining a low Mini-Cog score.
The IADL scale is an instrument to assess independent living skills. More precisely, it provides information about 8 skills necessary for living in a community, for example food preparation, housekeeping and laundering. Individuals are scored according to their highest level of functioning in a specific category. A summary score, therefore, ranges from 0 (low function, dependent) to 8 (high function, independent).
Then, MMSE may be administered. It consists in a 30-point questionnaire including questions and problems in many areas: orientation to time and place; repetition of lists of words; attention and calculation; registration recall; speaking back a phrase; basic motor skills, such as drawing figures previously shown. Any score greater than or equal to 24 points indicates a normal cognition. Below this, the score can indicate severe (≤9 points), moderate (10-18 points) or mild (19-23 points) cognitive impairment.
In conclusion of the second stage, additional well-known tasks, not included in standard tests, may be administered, for example matrix and trail making tests. Then, a second signature of the subject is acquired.
It is worth noting that all these tests already include handwriting tasks, and their contribution and importance within the tests has been already clinically validated. In this case, the use of a digital on-line (real-time) acquisition tool gives the possibility to acquire kinematic features.
Furthermore, it is worth remarking that the inclusion in the proposed protocol of standardized cognitive tests helps in specifying the stage of disease of the example acquired, resulting in a multiclass classification problem. 3.3
The tasks described within the previous two paragraphs have three major advantages: • They are useful for doctors to perform the assessment as they usually do; • They can provide the so called “ground truth” to be used in the research activities; • They provide a set of extra data to be combined (for analysis and classification aims) to those related to handwriting.
Among the various tasks proposed by the literature, the following ones were
observed to be the most employed and discriminant:
• Archimedes spiral drawing;
• Copying the details of a check into the appropriate places;
• Repetitions of the cursive letters “l” and “e”;
• Writing a dictated word and sentence. Note that, in order to keep the dictation speed
constant, an audio trace should be preferred to the examiner’s voice. Moreover, note
that, according to [
In addition, following (with the pen) a trajectory drawn on the screen may be of interest to assess the hesitation of the subject in performing such a task.
Clearly, the handwriting tasks have to be administered not only to impaired patients but also to healthy controls, in order to provide examples for both kinds of subjects.
A summary of the handwriting tasks included in all the three stages of the protocol is reported in Table 1. 4
In this paper, an integrated protocol for the assessment of neurodegenerative diseases has been proposed. It integrates handwriting tasks to a digitized version of standard cognitive and functional tests.
Initial screening
Signature
Trail making test
Signature Handwriting Archimedes spiral
Copying the details of a check Repetition of “l” and “e” Word/sentence writing
Trajectory following
On one hand, the protocol may be useful, to the research community, to collect different handwritten traits. One main open issue, in fact, concerns the development of a large benchmark database so that different pattern recognition tools can be effectively evaluated and compared. At the same time, the protocol may be of real use for doctors to support their daily activities. The inclusion of standardized tests is also important to specify the stage of the illness of the patterns acquired: indeed, the main open problem is to support the early diagnosis of the disease.
Future developments of our research should face some open issues. First, the protocol must be implemented and validated in a real-world scenario. The use of a digitizing tablet may be unfamiliar to elderly people; therefore, a comparative study between this acquisition modality and the usual one based on pen and paper should be carried out in order to evaluate if any bias is introduced. Second, other characteristics of the participants, for example the medical treatment, should be taken into account.
This work was supported by the Italian Ministry of Education, University and Research within the PRIN2015-HAND Project under Grant H96J16000820001.