Learning More from Finger Tapping in Parkinson's Disease: Up and Down from Dyskinesia to Bradykinesia

The finger tapping test evaluates bradykinesia, focusing on decrement in rate, amplitude, or both with repetitive action. Vertical positioning of the hands during this task may also be clinically relevant. We developed a TAP score, measuring the vertical level above the lap where the patient performs the finger tapping ranging from 1 (task performed with the hand close to the lap) to 4 (above the head). In this pilot study, we retrospectively applied the TAP score in addition to usual motor scales during acute levodopa challenge in 123 PD patients (of whom 88 presented L-dopa-induced dyskinesia [ LID]). TAP ON was higher than TAP OFF. Patients with LID presented higher TAP ON. TAP ON was related to LID severity, whereas TAP OFF was inversely related to the OFF motor symptoms. The TAP score may be a measure of proximal movement amplitude representing an easy method to evaluate defective or excessive motor output in patients with advanced disease.