Assessments of axial motor control during deep brain stimulation in Parkinsonian patients

OBJECTIVE: We tested the hypothesis that bilateral deep brain stimulation ( DBS) in the globus pallidus internus or the subthalamic nucleus improves va rious components of postural and oromotor function and that some of the com ponents correlate with changes in the Unified Parkinson's Disease Rating Sc ale (UPDRS) in patients with Parkinson's disease. METHODS: Six patients with Parkinson's disease were evaluated for four post ural and two orofacial UPDRS items, and quantitative tests of posture adjus tments and oromotor control were performed while the patients were on and o ff DBS. Measurements of postural adjustments included reactive force and la tency before a voluntary step. The oromotor assessments involved velocity a nd amplitude changes during voluntary jaw movement. RESULTS: DBS significantly improved the total UPDRS motor score by an avera ge of 44%, which included improvement of 18 to 54% in the postural and orof acial items. DBS also decreased foot lift-off latency significantly, but it produced a variable response to the preparatory postural force in the swin g limb. DBS significantly improved jaw-opening velocity by 14 to 50% and ja w opening amplitude by 5 to 41%. Significant correlations for the percentag e change from off and on DBS occurred among a few UPDRS items and foot lift -off latency and jaw-opening velocities. CONCLUSION: DBS in either the globus pallidus internus or the subthalamic n ucleus induces improvements in bradykinesia of specific components of postu ral and oromotor control, which also can be measured by the postural and or ofacial UPDRS items. In some Parkinson's disease patients, DBS results in i mprovements in force or amplitude control, although these changes are not r eflected in changes in UPDRS postural and orofacial items. A battery of qua ntitative and clinical tests must be used to evaluate the effects of DBS on axial motor control adequately.