UPDRS items, namely the Leg Agility (LA) and the Sit-to-Stand (S2S) tasks, giving particular emphasis to their kinematic characterization, to the performance evalua-tion of the automatic scoring system, to the comparative analysis of the three tasks, and, finally, to the opportunities that such a system can offer in the context of tele-medicine.
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3.1.1 The Leg Agilit, Sit-to-Stand, and Gait UPDRS Tasks
The LA, Arising from Chair,1and G tasks correspond to the items 3.8, 3.9, and 3.10 of the MDS-UPDRS document [79].
The choice of these particular tasks was influenced by the need to keep the BSN as simple as possible, maximizing at the same time the number of tasks which could be analyzed without changing the sensors’ placement. The selected tasks are partic-ularly suitable for the considered unified analysis and clinically relevant for a com-prehensive evaluation of the patients’ symptoms, as they refer to different aspects of PD (for example, LA is related to bradykinesia while S2S and G are associated with posture/deambulation symptoms). The evaluation of UPDRS motor tasks is usually performed without the support of any technological instrument so that the neurologist assesses the task in a qualitative way and relies especially on his/her experience and training. Therefore, assessments may vary from neurologist to neurologist (inter-rater variability) or from one to another evaluation session by the same neurologist (intra-rater variability) [80]. In the following, a brief description of each task is provided.
Leg Agility Task
Table 3.1: UPDRS mapping for LA task.
UPDRS Amplitude Hesitations Interruptions Slowing Freezing
0 nearly constant no 0 0 0
1 decrements near the end slight ≥ 1 1,2 0
2 decrements midway mild - 3,4,5 0
3 decrements after first tap moderate - ≥ 6 ≥ 1
4 always minimal or null severe - always
-In the LA task, the patient is asked to sit on a chair provided with rigid backrest and armrests. The patient must place both his/her feet on the floor in a comfortable position. The exercise consists in alternately raising up and stomping the feet on the ground, as high and as fast as possible. Ten repetitions per leg must be performed
1For consistency other works in the literature [96, 97], in the following we denote the Arising from Chair task as S2S task.
while sitting on the chair in order to test each leg separately (in the following, we will distinguish between Right LA (RLA) and Left LA (LLA) tasks).2The examiner should first train the patient, showing him/her the correct execution of the exercise, stopping as soon as the patient starts. The significant parameters that have to be mea-sured, independently for each leg, are the speed, the regularity, and the amplitude of the movement. In Table 3.1, an attempt to map the characteristics of the LA task, which the examiner should consider for the assessment of the patient’s performance, to the UPDRS scores is shown. We recall that UPDRS scores are integers values, ranging from 0, which means that the patient is able to perform the task normally and with no impairments, to 4, which means that the patient has severe difficulties in performing the exercise or is not able to perform it at all.
Sit-to-Stand Task
Table 3.2: UPDRS mapping for S2S task.
UPDRS Failed attempts Use of armrests Slowing Move forward on chair
0 0 failed attempts no no no
1 ≥ 1 failed attempts no yes yes
2 0 failed attempts yes -
-3 ≥ 1 failed attempts yes -
-4 not able to stand up alone
In the S2S task, the patient is asked to sit on a straight-backed chair with armrests.
The exercise consists in crossing the arms across the chest (in order to avoid their use in the movement) and getting up from the chair. In the case of failure, the patient can retry to raise up to two more times. If still unsuccessful, the patient can move forward on the chair to facilitate the movement or, in case of another failure, he/she can use the armrests to stand up. After a maximum of three failed trials, the patient can move forward on the chair to facilitate the movement. If the patient is still not able to stand up, he/she is allowed to push off using his/her hands on the armrests. After a maximum of three unsuccessful trials with the help of the arms, the examiner can
2When not specified, LA refers to the general task, including both RLA and LLA trials.
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eventually help the patient to stand up. The mapping between the key characteristics of the S2S task and UPDRS scores is shown in Table 3.2.
Gait Task
Table 3.3: UPDRS mapping for G task.
UPDRS Independent walking Impairments level
0 yes no impairments
1 yes minor impairments
2 yes substantial impairments
3 no assistance device needed for safe walking
4 no cannot walk at all or only with another person’s assistance
The description of the G task and the main aspects that the examiner should take into account for assigning an UPDRS score in this task have been provided in Section 2.1.4. Similarly to the LA and S2S cases, a possible mapping between the task characteristics and the UPDRS evaluation is shown in Table 3.3.
3.1.2 Chapter Contribution
Unlikely the majority of the existing literature, in which UPDRS tasks are analyzed singularly, in this chapter we focus on the comparative evaluation of the LA, S2S, and G tasks. The same approach uses for the study of the G task has been extended to the LA and S2S tasks, through an experimental analysis of the data from 34 PD patients and the UPDRS evaluations of three expert neurologists [2, 4]. A common, low-complexity BSN, formed by three IMUs (two on the thighs and one on the chest) has been used for characterizing the considered tasks by extracting and analyzing the kinematic features associated with their typical movement patterns, in both time and frequency domains. The most relevant features has been identified and analyzed for quantifying the motor performance of patients belonging to the different UPDRS classes. The extracted features and the subjective evaluations by neurologists have been then used to train an automatic UPDRS scoring system, with the aim to auto-matically assess the patients’ motor performance matching as closely as possible the
medical evaluation criteria. The performance of the automatic assessment has been analyzed and discussed proposing a comparative outlook with the inter-neurologist assessment. We have also investigated the correlation between the UPDRS scores assigned to the tasks by both the neurologists and our automatic system, introduc-ing a an aggregate UPDRS score as a significant concise metric which can provide additional information to neurologists for deriving insights on the overall level of im-pairments of patients and on the relative “weight” of each task in the assessment of the gravity of the symptoms. Finally, the feasibility of an application for remote reha-bilitation and monitoring of PD patients in a tele-medicine environment is discussed and a possible efficient implementation approach is proposed.