Deep brain stimulation (DBS) can effectively reduce tremor in people with Parkinson’s disease, regardless of the brain region stimulated, according to a recent review study.
The review, “STN vs. GPi deep brain stimulation for tremor suppression in Parkinson disease: A systematic review and meta-analysis,” was published in the journal Parkinsonism & Related Disorders.
Tremor is a main symptom of Parkinson’s disease, strongly affecting patients’ quality of life. It is estimated that 47-90% of Parkinson’s patients have an action tremor and 76-100% have a resting tremor.
Reduction of tremors is an important goal in Parkinson’s treatment, and could have a significant impact in patients’ well-being and everyday life. However, tremor is difficult to treat and often does not respond to anti-tremor medications.
Deep brain stimulation — electric stimulation in strategic brain areas through surgically implanted thin wires in the brain — is used to treat people with advanced Parkinson’s disease whose motor symptoms, such as tremors, are not reduced with medication.
Several studies have shown that DBS eases motor symptoms, reduces the necessary daily dose of medication, and improves patients’ quality of life.
Currently, the main approved targets for DBS in Parkinson disease are the subthalamic nucleus (STN) and the globus pallidus interna (GPi), areas of the brain involved in motor function.
While recent studies have found no significant differences between the therapeutic effects of the stimulation of both targets, many clinicians maintain an older preference for STN over GPi, due to a supposedly greater reduction in tremors and in medication.
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However, evidence supporting STN-DBS superiority in tremor suppression is limited.
Researchers have conducted a systematic review of all randomized clinical studies comparing the therapeutic effects of STN-DBS and GPi-DBS on tremors in Parkinson’s patients, published before March 2017.
Their search identified five suitable longitudinal randomized control trials with five years follow-up data. The data included the two DBS targets, STN and GPi, and tremor sub-scores of the Unified Parkinson’s Disease Rating Scale (UPDRS) before and after DBS, and with or without dopaminergic medication.
Their analysis showed that deep brain stimulation significantly reduced tremor symptoms in Parkinson’s patients, and that these effects were observed regardless of medication status.
When looking at the two targets of deep brain stimulation, researchers found that both methods reduced tremor severity in Parkinson’s patients, with no significant differences between them. These results support that DBS of each target promotes similar long-term benefits on tremor.
However, analysis of therapeutic effects on tremor over the course of five years showed that STN-DBS was more effective to reduce tremors after two and five years than at the first six months. In turn, GPi-DBS showed a more stable degree of effectiveness on tremors over time.
“Although both targets were effective, practitioners should be aware that it is possible one target could appear superior in studies depending on the duration of follow-up,” researchers wrote.
They also noted that when Parkinson’s patients present with tremor as the primary complaint, or as an issue adversely affecting quality of life, selection of deep brain stimulation target should focus on the presence of other problems “such as cognitive impairment, speech difficulties, presence of mood disorders, and presence of impulse control disorders.”
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