Does deep brain stimulation of the nucleus ventralis intermedius affect postural control and locomotion in Parkinson's disease?

The purpose of this study was to evaluate the effect of unilateral stimulat ion of the nucleus ventralis intermedius (VIM) on parkinsonian signs like p ostural stability and locomotion with respect to the severity of Parkinson' s disease (PD). Seven patients with idiopathic PD were included in the stud y. Changes in visual cues on postural stability and step initiation were as sessed on a fixed platform system with VIM stimulation switched either on ( VIM ON) or off (VIM OFF), and compared with a control group of seven age-ma tched normal individuals. Sway scores (area and path) were significantly (p <0.05) higher in the parkinsonian patients with VIM OFF than with VIM ON a s well as compared with the control subjects. No correlation was obtained b etween extent of sway scores and severity of contralateral tremor after ces sation of VIM stimulation. Locomotion parameters, by contrast, were not inf luenced by VIM stimulation: latency until step initiation and walking-cycle time were the same among parkinsonian patients as among normal individuals , both in the presence and in the absence of VIM stimulation. In conclusion , our results indicate that tremor suppression by VIM stimulation improves postural stability.