Quadruple Misfolded Proteins, Alzheimer's

5 Things You Should Know About the Link Between Parkinson’s and Dementia

By Lecia Bushak | October 31st, 2019

Both Parkinson’s disease and dementia were ravaging the brain and behavior of actor Robin Williams before his death, but at the time, he didn’t realize he had the latter.

Despite the fact that the signs of this combination can be confusing, the double diagnosis of Parkinson’s and dementia impacts a large number of people. Of the one million people who have Parkinson’s in the U.S., 50 to 80 percent may have dementia—either as a result of Parkinson’s pathology, or separately.

Robin Williams’ widow, Susan, wrote an editorial published in Neurology that was addressed to neurologists after his death. In it, she shared what it was like seeing her husband experience both Parkinson’s disease and Lewy body dementia firsthand.

“My hope is that it will help you understand your patients along with their spouses and caregivers a little more,” Susan wrote.

Williams was first diagnosed with Parkinson’s disease, which at first seemed to provide some answers for his out-of-character symptoms.

But it wasn’t until after his death that an autopsy revealed he had been in the later stages of Lewy body dementia—a common form of dementia characterized by deposits of Lewy body proteins in the brain, which can impact physical movement, mood, memory and behavior.

“I will never know the true depth of his suffering, nor just how hard he was fighting,” Susan wrote. “But from where I stood, I saw the bravest man in the world playing the hardest role of his life.”

If you or a loved one are concerned about having either of these diseases and want to learn more about their effects on the brain, here are the most important things you should know.

The pathologies are different, but many of the symptoms can be similar

“We do know that the pathology is quite different” between Parkinson’s and dementia, said Dr. Odinachi Oguh, a neurologist at the Cleveland Clinic Lou Ruvo Center for Brain Health. “But the processes in which memory is impacted in both diseases is about the same.”

“From the pathology standpoint, both diseases are characterized by a neurodegenerative process,” Oguh said. “The neurodegeneration results in abnormal accumulation of protein, which builds up and becomes toxic to the brain.”

Alzheimer’s, for example, affects memory areas of the brain, which include the temporal lobes, as well as the memory center, or hippocampus. Parkinson’s, meanwhile, starts in the basal ganglia part of the brain, and as the disease progresses, it can also affect the memory center, resulting in forgetfulness, an early sign of Alzheimer’s or other forms of dementia.

There’s a spectrum of pathologies

Scientists have been examining this link—and how the two diseases often overlap—for some time, but still aren’t completely certain how they contribute to one another. As a result, physicians sometimes group the diseases into different combinations when making diagnoses.

Dementia in Parkinson’s patients can present itself in varying forms. In some cases, the Parkinson’s pathology can trigger the dementia pathology—a situation that results in what’s known as Parkinson’s disease dementia, says Dr. Aaron Ritter, Director of the Clinical Research Program at the Cleveland Clinic Lou Ruvo Center for Brain Health.

“A substantial subset of folks with Parkinson’s who live long enough, will develop [Parkinson’s disease] dementia,” Ritter said. “It’s separate from Alzheimer’s, but it’s likely related to Parkinson’s pathology, a sort of spreading of Parkinson’s.”

In other cases, patients may develop a form of dementia like Alzheimer’s separately from their Parkinson’s disease, though this isn’t visible until after death, through an autopsy.

Many people with Parkinson’s may also develop Lewy body dementia shortly after their diagnosis. “When you have Parkinson’s, and see cognitive decline—or things like hallucinations and delusions—up to a year after your Parkinson’s diagnosis, you may have Lewy body dementia,” Oguh said.

Ultimately, Ritter said, scientists are beginning to accept that there’s likely a wide spectrum of different pathologies that can develop in each individual. Studying those is the goal of the COBRE study at the Cleveland Clinic, which Ritter works on.

“Being able to study and acknowledge that there’s a spectrum of different pathologies in different people’s brains is how we’re approaching it,” Ritter said. “We’re going through genetic, inflammatory, cognitive data; as well as clinical data like head traumas, medications and family history, to see if we can differentiate [pathologies in Parkinson’s and dementia]. We’re trying to get a very deep-dive into what may shape an individual’s aging process [in the brain].”

Not everyone with Parkinson’s will develop dementia

Despite the fact that the pathology of Parkinson’s disease can trigger the development of different types of dementia, not everyone with Parkinson’s will develop dementia. About 30 percent of people with Parkinson’s will actually not develop dementia at all, as stated by the National Parkinson Foundation.

However, “the vast majority of people with Parkinson’s may experience some form of cognitive impairment over time,” the foundation says.

See a doctor if you’re noticing symptoms beyond Parkinson’s

Sometimes the mood or memory changes a person experiences cannot entirely be explained just by Parkinson’s. If this is the case, “the caregiver should explore other diagnoses, because if something cannot be explained by Parkinson’s, there’s certainly a risk of it being dementia,” Oguh said.

She added that some signs to look for include increased memory and behavioral problems, like mood swings, anxiety or depression. Psychiatric behaviors, like hallucinations, delusions or paranoia, cannot just be explained by Parkinson’s, and are more likely to be caused by a form of dementia like Lewy body dementia.

Oguh urged caregivers to be aware of changing symptoms like these.

“I think sometimes family members are able to realize [the symptoms] sooner than the patient,” Oguh said. “Often the patient might lack insight as to what is happening. I would encourage family members to seek expert opinion and treatment options.”

There’s no cure for the diseases, but some therapies may help

Certain drugs, like cholinesterase inhibitors and antipsychotic medications, are prescribed as treatment for people with Parkinson’s and dementia. And lifestyle changes—from improved diet, sleep, exercise and socializing—have been shown to have beneficial effects on patients with these diseases.

Oguh noted she hopes that improved treatments that will help some of the emotional and behavioral problems in these patients will be on the horizon soon.

“I’m hoping that with the new advances in medication, we’ll be able to control [Parkinson’s and dementia] better,” Oguh said. “I believe there will be better medication to improve cognition in patients, and that that will be seen in the next five to 10 years.”

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