Parkinson's Surgery Study Shows Better Dyskinesia Treatment

A recent study has found a preferential form of deep brain stimulation (DBS) surgery that better treats dyskinesia in advanced Parkinson's disease (PD) patients.

In a comparison of globus pallidus interna- (GPi) and subthalamic nucleus- (STN) targeted DBS surgery treatment among Parkinson's patients, researchers found surgery focused on the GPi better improved patients' gait disturbance, postural instability, and dyskinesia — common effects from the neurodegenerative disorder.

The study, which ran from April 2002 through May 2014 in the Departments of Neurology and Neurosurgery at the Asan Medical Center in Seoul, Korea, entailed 147 patients diagnosed with advanced PD who received either form of the DBS surgery.

The two focused forms of DBS surgery are a common treatment for advanced PD when medication can no longer adequately treat a patient's motor symptoms, according to the study. Researchers noted GPi and STN DBS have been documented as similarly effective treatments for improving motor symptoms over the course of 2-3 years — but there has been little research into the advantages and disadvantages of either.

Researchers — led by Ho-Sung Ryu (pictured), PhD, of the Department of Neurology and the University of Ulsan College of Medicine in Seoul — analyzed patients over the 12-year span to have received either of the two forms of DBS. The therapeutic effects of each surgery were scored on the Unified Parkinson's Disease Rating Scale (UPDRS) and rate levodopa equivalent dose (LED) treatment after 12 months post-operation and compared with patients' baseline scores.

Despite dyskinesia and other motor symptoms being moreso improved in patients to have received GPi DBS, the first-year results of UPDRS scores showed little difference between the two treatments. 
STN DBS patients also had more improvement in LED scores, leaving researchers to consider a customizable approach to advanced PD treatment.

"It is still unclear whether there are definite advantages or disadvantages in selecting one target over another for DBS in patients with advanced PD," the study reads. "One target may improve a certain specific clinical symptom more effectively than another target."

Researchers also surmised DBS' therapeutic effects and influence on quality of life may be influenced by varying post-operative medications in different countries.

Parkinson’s, currently the one of the most common neurodegenerative disorders in the world, is frequently treated with levodopa or dopamine agonist therapies. But after 5-10 yeas of this treatment, PD patients may develop medication-related motor complications, such as Tardive Dyskinesia, according to the study.

Such complications cannot be treated with further adjustments in medication therapy, and the patients become candidates for DBS surgery. 

The study’s patients treated with GPi DBS received “much more LED” treatment at the first year post-operative mark than their STN DBS counterparts, suggesting PD patients could receive more LED treatment without the effects of dyskinesia if having received GPi DBS.

Dyskinesia has been previously associated with reduced pallidal firing rates, altered firing patterns, and increased pallidal neuronal synchronization at low frequencies, according to the study. Therefore, researchers believe the concept of GPi having a greater effect on dyskinesia could be further supported by literature on dyskinesia’s pathogenic mechanisms.

Adversely, there are other studies that have reported patients having had similar improvements in levodopa-induced dyskinesia following DBS on either region. Researchers concluded there are more studies needed to investigate exactly how DBS effects dyskinesia in its targeted regions.

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