Objective: To design a pilot study to analyze ballistic movements in Parkinson’s disease patients with levodopa-induced dyskinesia.

Background: Ballistic movements are characterized by an electromyographic (EMG) triphasic pattern, consisting of two bursts of agonist muscle activity (AG1 and AG2), separated by an “electrical silence” in which a burst of EMG activity from the antagonist (AT) musculature coexists. They have been widely studied in patients with movement disorders but have not been measured in patients with Parkinson’s disease with levodopa-induced dyskinesias.

Method: The muscular activity of the flexor and extensor muscles of the forearm was recorded with EMG surface electrodes, and the movement of the wrist was measured with a uniaxial accelerometer. EMG durations of the AG1 and AT intervals and the amplitude of each component’s electromyographic signal (defined as the area under the curve of rectified-EMG activity), and the amplitude ratio of the agonist and antagonist EMG component (AG1 / AT ratio) were measured.

Results: A total of 9 subjects were included: 3 patients with PD without motor complications/dyskinesias; 3 patients with PD and dyskinesias during the ON state; and three healthy controls. Dyskinetic PD patients were recorded in the OFF (no dyskinesias) and ON state (with dyskinesias). Patients with levodopa-induced dyskinesias preserved the triphasic pattern in EMG and the tonic inhibition of agonist muscles before the ballistic. An increase in the AG1 / AT ratio was observed in patients with dyskinesias, both in the OFF (2.4) and ON (2.3) state, compared to healthy controls (1.2) and non-dyskinetic PD (1.0); p=0,01.

Conclusion: These preliminary results suggest a dysregulation in motor control of the ballistic movement in PD patients who develop levodopa-induced dyskinesias, regardless of concomitant dopaminergic medication.
Wheter the increase in the AG1/AT ratio is due to an increment of the impulsive agonistic force or a decrease in the braking force from antagonistic muscle, needs to be elucidated. Furthermore, studies with a larger sample size are needed to verify the reproducibility of these findings.

References: Berardelli A, Hallett M, Rothwell JC, Agostino R, Manfredi M, Thompson PD, Marsden CD. Single-joint rapid arm movements in normal subjects and inpatients with motor disorders. Brain 1996; 119:661-74.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/ballistic-single-joint-arm-movements-in-levodopa-induced-dyskinesias-in-parkinsons-disease/