Accelerometric assessment of levodopa-induced dyskinesias in Parkinson's disease.

Our objective was to develop parameters for objective ambulatory measurements of levodopa-induced dyskinesias (LID) in patients with Parkinson's disease (PD). Twenty-three PD patients with mild to severe LID were submitted to a standardized protocol of 1-minute recordings during rest, talking, stress, and four activities of daily life (ADL). Patients were simultaneously monitored with portable multi-channel accelerometry (four pairs of bi-axial sensors mounted onto the most affected arm, leg, and at the trunk) and recorded by video. LID severity was assessed with a modified Abnormal Involuntary Movement Scale (m-AIMS). The signals were analyzed, and every 1/8-second interval the amplitude was obtained of the dominant frequency within 1-4 Hz and 4-8 Hz frequency bands (Amp1-4 and Amp4-8). For both measures, convergent validity, reproducibility, and responsiveness were determined. In absence of voluntary movements, a significant relation was found between Amp1-4 and Amp4-8 and m-AIMS. Repeated measurements during rest showed a high reproducibility (intraclass correlation coefficient = 0.90 [Amp1-4] and 0.86 [Amp4-8]). The extent to which LID increased with talking and stress correlated significantly (p = 0.02) between the objective and clinical measures (intraclass correlation for differences = 0.67). During ADL, LID occurred in a similar frequency band as voluntary movements and only Amp1-4 and Amp4-8 of the trunk and leg sensor remained highly correlated with m-AIMS. Although objective measures of LID are reliable and responsive, they fail to distinguish LID from voluntary movements. These measures are of value only when obtained during rest (all sensor sites) or during ADL when derived from those body segments that are normally not involved in these ADL tasks (trunk and leg).