Objective: To assess the utility of finger tapping (FT) test to evaluate bradykinesia in Parkinson’s disease (PD) at short and long FT sequences.

Background: Repetitive FT is commonly used to assess bradykinesia in PD. However, its clinical evaluation is not easy and low inter-rater reliability has been demonstrated. The new MDS-UPDRS was constructed to overcome the weak points of older scales. For FT, it instructs to rate only the first ten taps, which may appear too short compared to traditional recommendations to perform longer sequences of tapping to correctly evaluate bradykinesia.

Methods: 56 PD patients (26 F), mean age 65 (range 46-82), disease duration 14.5 (1-26) yrs with mild to moderate PD, mean Hoehn & Yahr stage 2 (1-3) were tested in the on-medication state. 62 (34 F) volunteers, of mean age 65 (41-83) yrs served as normal controls (NC). The FT subtest of the MDS-UPDRS was recorded by Optitrack V120 3D motion capture system during 15 s repetitive index finger-to-thumb tapping trials. Average tapping frequency (AvgFrq), maximum opening velocity (MaxOpV) and amplitude decrement (AmpDec) were computed using BradykAn software. The parameters were analyzed in the first 10 taps of each trial and in the whole 15 s sequences. In addition, videorecordings were blindly rated by two movement disorders specialists (KZ and ER) according to MDS-UPDRS.

Results: Expert ratings of FT significantly differed between PD patients and NC (median PD 1.5, NC 1.0; p<0.001, AUC = 0.77). MaxOpV discriminated PD from NC when measured in the first 10 taps (median PD 0.92 m/s, NC 1.27 m/s; p<0.001, AUC=0.75) as well as in the whole sequence of 15 s (PD 0.84 m/s, NC 1.18 m/s; p<0.001, AUC=0.78). For AmpDec, the difference in medians between PD and NC was 0.04 in the first 10 taps (PD 0.07, NC 0.03; p<0.001, AUC=0.72) and 0.12 in 15 s (PD 0.22, NC 0.10; p<0.001, AUC=0.86). AvgFrq did not show any difference between PD patients and NC.

Conclusions: Short sequence of 10 finger taps allows to recognize bradykinesia and to discriminate PD patients from NC with a resolution similar to long FT sequence. The MaxOpV parameter of 3D motion analysis shows similar resolution in both short and long sequences, while the AmpDec appear as the most sensitive parameter of bradykinesia only when measured in the whole sequence of 15 s. Grant support: Czech Ministry of Health, IGA NT 14181.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/evaluating-bradykinesia-how-many-finger-taps-are-needed/