Selective use of low frequency stimulation in Parkinson's disease based on absence of tremor.

BACKGROUND: High frequency stimulation (HFS) of the subthalamic nucleus is one of the most effective treatments for advanced Parkinson's disease (PD). HFS has provided beneficial improvements in the cardinal features of PD, but has not been proven as effective for addressing the axial predominant levodopa resistant symptoms, such as speech disturbances, gait disturbances, and postural instability. Recent studies have suggested that changes in stimulation parameters may influence differing PD symptoms. OBJECTIVE: The purpose of this study was to compare the effects of low frequency stimulation (LFS) versus HFS on the Unified Parkinson's Disease Rating Scale (UPDRS), gait, balance, and verbal fluency. METHODS: Eight tremor dominant and nine non-tremor dominant participants with bilateral deep brain stimulation of the subthalamic nucleus were tested off stimulation, during LFS, and during HFS. RESULTS: Results revealed that HFS significantly reduced UPDRS tremor score in the tremor dominant group; however no differences emerged within the non-tremor dominant group. No differences between groups or stimulation conditions were found for gait, balance, and verbal fluency measures. CONCLUSION: These results may suggest that HFS is better than LFS for reducing tremor in tremor dominant patients. However, patients with mild or no tremor show no acute differences in benefit from LFS as compared to HFS.