What is the efficacy of subthalamic 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

Subthalamic stimulation involves implantation of a deep brain stimulation (DBS) lead into the subthalamic nucleus (STN). Currently, it is the surgical procedure most commonly used to treat Parkinson disease (PD). STN-DBS controls all of the cardinal symptoms of PD, as well as motor fluctuations and dyskinesia. STN-DBS also often results in significant reductions in antiparkinsonian medications. On average, dyskinesia and antiparkinsonian medication use are reduced by 50–80%.

Candidates for STN-DBS include levodopa-responsive patients with medication-resistant disabling motor fluctuations or levodopa-induced dyskinesia (LID) without significant cognitive impairment, behavioral issues, or mood problems. Unilateral or bilateral STN stimulation is indicated in patients with advanced idiopathic PD who are still responsive to levodopa but suffer from severe fluctuations in medication response, tremor, rigidity, or akinesia in the “off” state (ie, when medications are not working) and LID in the “on” state. [29, 30]

Multiple studies have examined the effects of STN-DBS and documented significant improvements in the motor symptoms of tremor, rigidity, and bradykinesia, as well as activities of daily living. Long-term follow-up reports have shown that significant improvements in motor function and activities of daily living are maintained for up to 5 years after surgery. According to one study, STN-DBS also can increase the sleep quality of PD patients, as measured by the Parkinson's disease sleep scale (PDSS). However, the study did not show improvements in the Epworth Sleepiness Scale (ESS). [31]

A meta-analysis found that on average, doses of levodopa equivalents were reduced by 55.9% after STN-DBS; dyskinesia was reduced by 69.1%; daily “off” periods were reduced by 68.2%; and quality of life was improved by 34.5%. [32] “On” time is also significantly increased, from 27% of the day at baseline to 74% at 3 months. Improvement is usually stable, at least up to 5 years.

Bilateral STN stimulation may produce dramatic beneficial effects on midline symptoms such as gait, posture, and balance. A 1-year study of unilateral STN-DBS in 37 patients found significant bilateral benefit; these researchers suggested unilateral stimulation followed by a later contralateral procedure, if necessary, especially in patients with prominent asymmetry. [29]

Selected patients with PD derive significant benefit from neuroablation or stimulation at the ventral intermediate (VIM) nucleus or the globus pallidus pars interna (GPi), in most instances akinesia (ie, freezing) and gait abnormalities are not improved significantly. Unfortunately, these symptoms are commonly the most disabling features of advancing PD. Consequently, a great deal of attention has been paid to a new procedure—bilateral electrostimulation of the STN.

The substantial decrease in dosage and frequency of antiparkinsonian drugs that is possible after STN-DBS can have an additive effect to LID. In some cases, patients may experience severe dyskinesias necessitating the reduction of dopaminertic medications. Whereas some groups significantly decrease drug dosages immediately after surgery, the authors prefer to act more conservatively; many patients do not tolerate immediate dosage reductions and may experience significant mood abnormalities—in particular, apathy and depression.

By acting on the gating mechanism involved in response initiation, STN-DBS may produce improvement in motor function at the price of increasing certain types of impulsive behavior. [33] Positron emission tomography (PET) studies have correlated apathy after STN-DBS with local changes in glucose metabolism. [30]

Adverse events associated with STN-DBS can be classified into 3 main groups, including surgical, hardware, and stimulation-related (see Complications), which are better recognized and managed currently.


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