Quantitative analysis of finger and forearm movements in patients with off state early stage Parkinson's disease and scans without evidence of dopaminergic deficit (SWEDD)

Abstract

Background: Scans without evidence of dopaminergic deficit (SWEDD) is a radiological nomenclature which refers to patients with a normal dopamine transporter scan presumed to have parkinsonism. The motor features of SWEDD patients should be understood in order to avoid costly and inappropriate treatments. Therefore, it is important to effectively differentiate SWEDD from Parkinson's disease (PD) in the early stage of disease. As bradykinesia is a cardinal clinical feature of parkinsonism, we quantitatively investigated detailed presentations of hand movement using an angular measurement system in SWEDD and PD patients as well as normal controls. Methods: Twenty-three patients with SWEDD, 23 patients with off state early stage PD, and 23 age-matched healthy controls participated in this study. Angular velocity was measured during finger-tapping and forearm. rotation movement for the assessment of bradykinesia. RMS (root mean square) velocity and amplitude as well as movement irregularity were derived from the gyro sensor signal. Results: SWEDD patients presented a greater average speed, a larger average amplitude, and more regular speed and amplitude only during forearm rotation than PD patients (p < 0.05). SWEDD patients also exhibited a smaller average speed and average amplitude, and a more irregular speed on average during finger tapping than controls (p < 0.05). Conclusions: Quantitative variables of forearm rotation movement showed significant differences between SWEDD and PD patients, and quantitative variables of finger tapping movement showed a significant difference between SWEDD patients and the control group. These results suggest that quantitatively-assessed variables using biomedical engineering devices could aid clinicians in the identification of potential SWEDD.