What is the efficacy of pallidal deep brain stimulation (DBS) in the treatment of Parkinson disease (PD)?

Updated: Dec 09, 2020
  • Author: Konstantin V Slavin, MD; Chief Editor: Brian H Kopell, MD  more...
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Answer

Siegfrid and Lippitz introduced bilateral pallidal stimulation (ie, stimulation of the globus pallidus pars interna [GPi]) in 1994, reporting improvements in rigidity, akinesia, and levodopa-induced dyskinesia (LID) in 4 patients. [24] Subsequently, deep brain stimulation (DBS) in the GPi received much less attention than the comparable procedure in the subthalamic nucleus (STN), though the best overall target for Parkinson disease (PD) remains controversial. [25]

A 2005 comparative study by Anderson et al showed no significant differences in the overall benefits of DBS at these 2 sites. [26] Long-term studies up to 4 years after pallidal DBS have continued to show significant improvements in the cardinal features of PD and dyskinesia as compared with status for surgery.

Through the implantation of a DBS lead in the GPi, pallidal stimulation significantly controls all the cardinal symptoms of PD (tremor, rigidity, bradykinesia), as well as dyskinesia. Candidates for pallidal DBS include levodopa-responsive patients with medication-resistant disabling motor fluctuations or levodopa-induced dyskinesia without significant cognitive impairment, behavioral issues, or mood problems.

Benefits ranging from 37% to 39% on the “off-medicine” Unified Parkinson Disease Rating Scale (UPDRS), a widely accepted rating scale of PD signs, have been reported. [26, 27, 28]

Dyskinesia has been shown to improve dramatically, and GPi-DBS has also been effective in improving motor fluctuations. The effect on tremor is less dramatic, and significant medication reduction is usually not achieved with GPi-DBS. On the other hand, cognitive and behavioral adverse effects seem to be less frequent.

Stimulator programming is more challenging in the globus pallidus than in the thalamus. Higher stimulation voltages may exacerbate freezing, nullifying the therapeutic effects of levodopa. Moreover, stimulation in different regions of the globus pallidus may have strikingly different effects. Dorsal GPi stimulation has been reported to improve akinesia and rigidity but may result in abnormal involuntary movements (ie, dyskinesias). In contrast, ventral GPi stimulation can exacerbate akinesia and gait abnormalities but improves rigidity and LID.


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