Even though Parkinson’s disease is best known for causing physical symptoms, such as difficulty walking and tremors, up to 80% of those affected by the movement disorder eventually develop dementia.

This sobering fact creates a dilemma when a treatment known as deep brain stimulation (DBS), which some research has suggested increases dementia risk, is recommended for people with Parkinson’s disease.

Why use DBS? In cases of more advanced Parkinson’s, the treatment has been shown to work better than medication at controlling motor symptoms caused by the disease, such as disabling tremors. DBS requires a surgical procedure to implant electrodes into areas of the brain that control movement, and a pacemaker-type device is implanted into the chest area. The pacemaker sends electrical signals to the brain to reduce abnormal movements.

Analyzing the risk: To better understand the potential dementia risk posed by DBS, researchers followed 175 people (average age 56) with Parkinson’s disease who received DBS implants after being diagnosed with the disorder for an average of 12 years. The study participants were checked for evidence of dementia at one, five and 10 years after the DBS implant. The key results of the study were published in Neurology, a journal of the American Academy of Neurology (AAN)…

  • After one year, 2.3% of patients developed dementia.
  • After five years, 8.5% of patients developed dementia.
  • At 10 years, nearly 30% had developed dementia.

“These rates are not higher than those reported in the general population of people with Parkinson’s,” said study author Elena Moro, MD, PhD, professor of neurology at Grenoble Alpes University in Grenoble, France, and a fellow of the AAN. “The few studies that are available with similar disease duration have reported higher rates of dementia.”

Caveats: The lower rate of dementia in those who received DBS may be due, in part, to the younger average age group of study participants. The lower incidence of dementia also could be explained by the relatively high percentage of participants who could not be located or failed to respond to the researchers’ requests for follow-up. For example, at the study’s 10-year mark, only 104 of the 175 study participants were available for testing.

The researchers also evaluated risk factors for dementia. As with all people with Parkinson’s disease, study participants who were male, older, had experienced hallucinations or scored low on thinking tests prior to the DBS surgery were more likely to develop dementia. The only risk factor that could be linked specifically to DBS was bleeding into the brain (cerebral hemorrhage) at the time of implant surgery.

“These results are very encouraging for people with Parkinson’s and their families that they can take advantage of the benefits of deep brain stimulation without worrying about it increasing the likelihood of developing dementia,” explained Dr. Moro.

Takeaway: Even though DBS does not cure or slow down the progression of Parkinson’s disease, it does improve quality of life for many people. This study shows that the treatment may be safer than some previous research has suggested.

Source: The study “Dementia and Subthalamic Deep Brain Stimulation in Parkinson Disease,” led by researchers at Grenoble Alpes University in Grenoble, France, and published in Neurology.