Summary

Dopaminergic medication or deep brain stimulation of the subthalamic nucleus (STN DBS) impact on many aspects of the grip–lift task in idiopathic Parkinson's disease (PD). The rate of both grip- and load-force generation were normalized by the levodopa test, whereas the maximum vertical acceleration was not improved in all studies. Other dopa-responsive factors included load preparation time, which was shortened, and maximal grip force that showed an extra increase in the test. The overflow of grip force and maximum negative load force was correlated with the intensity of levodopa-induced dyskinesias (LID) in patients affected by this symptom. Maximal negative load force and tremor were not dopa-sensitive. Subthalamic nucleus DBS exerted a dopa-like effect on most parameters of the grip–lift task except for grip force in the long-term comparison. In patients with LID the preoperative overflow of force in on-state and the severity of LID were both ameliorated by STN-DBS, although the force level did not return to normal values in all studies. A dopa-resistant action tremor of higher frequency can be seen during the grip–lift task, while the rest tremor of PD is suppressed at onset of the movement. Further therapies involve facilitation of movements with a training augmented by external cues like auditory or visual signals to overcome akinesia. The grip–lift task offers a valuable instrument to study therapeutic effects in PD.

Introduction

Dopaminergic medication or deep brain stimulation of the subthalamic nucleus impact on almost any aspect of motor deficits in idiopathic Parkinson's disease (PD).