Tests of manual dexterity and speed in Parkinson's disease: Not all measure the same.

INTRODUCTION Timed performance tests were introduced to overcome the disadvantages of subjective evaluation of bradykinesia in Parkinson's disease (PD). We aimed to verify their discriminative properties and compare them with the motion capture analysis of finger tapping. METHODS We included 22 PD patients (10 M, 12 F), mean age 64 (range 48-82) yrs, Hoehn & Yahr stage 2 (1-2.5) and 22 (10 M, 12 F) normal controls, mean age 66 (41-82) yrs. The key tapping subtest of the Halstead-Reitan battery, the Purdue Pegboard test, and the Bradykinesia-Akinesia Incoordination (BRAIN) test were performed according to the test manuals. The finger tapping subtest of the UPDRS-III, item 23 was recorded using a contactless 3D motion capture system Optitrack-V120. Average frequency (AvgFrq), maximum opening velocity (MaxOpV) and amplitude decrement (AmpDec) were computed and simultaneous video recordings of finger tapping were rated by two experts. RESULTS The AmpDec and MaxOpV motion capture measures best differentiated between PD patients and controls (AUC = 0.87 and 0.81). Of the instrumental tests, only the Purdue Pegboard attained significance in differentiating PD patients from controls (AUC = 0.80). In PD patients, MaxOpV correlated with the finger tapping ratings and BRAIN test, and AvgFrq correlated with the BRAIN and Halstead-Reitan test scores. Moreover, correlations were found between the Purdue Pegboard and finger tapping ratings. CONCLUSIONS Contactless 3D motion capture of finger tapping allowed an independent analysis of individual components of bradykinesia, demonstrating the amplitude decrement and maximum opening velocity as the most powerful discriminators between PD patients and controls.