Parkinson's Disease Research Roundup: September 2018

Nearly one million people in the United States live with Parkinson's disease. While tremor is the condition's best-known symptom, Parkinson's can include a wide range of symptoms, including balance issues, muscle stiffness, and memory problems.

For most people with Parkinson's, the cause is unknown. Understanding the risk factors for Parkinson's can help direct scientists toward new options for treatments, and ultimately preventing or curing the disease.

We've gathered some of the latest research into the underlying causes behind Parkinson's, and how the condition may be better diagnosed and treated.

An eye scan to diagnosis Parkinson's?

Currently, there is no objective test, such as a brain scan or blood test, to diagnosis Parkinson's disease. Doctors instead perform a neurological examination and look for a few cardinal symptoms, such as resting tremor and gait problems.

New research suggests that doctors may one day be able to diagnosis Parkinson's through an eye exam.

The study found that people with early-stage Parkinson's experience a thinning of their retinas. The scientists also found that the thinner the retina, which is made of a layer of nerve cells, the more dopamine loss shown on a brain scan. Patients with thinner retinas also experienced more severe Parkinson's symptoms.

Researchers hope their findings can eventually lead to the development of a simple eye scan for diagnosing Parkinson's.

Learning more about pain in Parkinson's

Pain is one common part of Parkinson's that can be difficult to pinpoint. Sometimes, pain may be related to other Parkinson's symptoms such as dystonia – prolonged muscle contractions – or muscle stiffness.

A new study sought to learn more about pain in Parkinson's that was not directly connected to other causes. Prior research has found that deep brain stimulation treatment for motor symptoms in a part of the brain called the subthalamic nucleus also treats Parkinson's-related pain.

Researchers hypothesized that pain in Parkinson's may be related to the way information related to pain is sent to the brain. To learn more, the research team looked at how rats with Parkinson's experienced pain. The rats with Parkinson's showed more activity with their subthalamic nucleus. The researchers also looked at rats with a damaged subthalamic nucleus, and found that those rats experienced delayed pain. Taken together, they concluded that the subthalamic nucleus does cause Parkinson's-related pain.

Next, they researched where pain signals to the subthalamic nucleus were coming from. The blocked two brain structures known to be important in sending damage signals from the spinal cord: the superior colliculus and the parabrachial nucleus. By blocking those brain structures, they saw that a direct communication pathway exists between the parabrachial nucleus and the subthalamic nucleus.

Based on those findings, the research team concluded that pathway is most likely involved in how deep brain stimulation treats pain in Parkinson's. Researchers believe that better understanding which pathways are involved may help researchers develop new treatments for pain in Parkinson's.

A connection between ADHD and Parkinson's disease?

Adults diagnosed with attention deficit hyperactivity disorder (ADHD) and adults prescribed ADHD medications are more likely to be diagnosed with early-onset Parkinson's and Parkinson's-like diseases, according to findings from a new study.

The retroactive study looked at medical records in the Utah Population Database between 1996 and 2011, analyzing 31,769 individuals diagnosed with ADHD or other hyperactivity disorders.

Researchers found that those diagnosed with ADHD were more than twice as likely to develop early-onset Parkinson's (a diagnosis before age 50).

ADHD patients who had been prescribed psychostimulants to treat the condition had a sixfold to eightfold increased Parkinson's risk.

The study builds on past research on the connection between methamphetamines (meth) abuse and Parkinson's. In that study, those who had used meth and amphetamines had a threefold risk of developing ADHD.

Legal amphetamines are prescribed to treat ADHD, so researchers were interested in researching whether much lower doses of amphetamines may also have an impact on Parkinson's risk.

But the researchers caution that the link between ADHD, Parkinson's, and ADHD medications is “not causation” – more research is needed to understand how these conditions and treatments are related.

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