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Parkinson’s hallucinations and brain disconnections

Researchers have identified areas of the brain that, when they become disconnected, may contribute to hallucinations associated with Parkinson’s disease.

Hallucinations are thought to be a side effect of long term use of Parkinson’s medications, but it has been unclear how these drugs change the brains of sufferers like Robin Williams.

Parkinson’s patients’ brains show failures of communication between different regions, but patients with hallucinations had additional neural disconnects.

The researchers at VU University Medical Center (VUMC) in Amsterdam, the Netherlands, found that those patients with hallucinations had disconnections between additional regions of their brains used in visual information processing and attention.

Researchers at VU University Medical Center Amsterdam used high resolution magnetic resonance images to compare the differences in the brains Parkinson’s patients with hallucinations (bottom) and without hallucinations. They found disconnections between areas of both groups, but the brains of those with hallucinations had additional disconnections that interfere with their abilities to process visual information and attention

Parkinson’s disease itself causes the death of neurons, particularly neurons that release the neurotransmitter dopamine. Dopamine carries signals through the brain that control movement, among many other functions.

The loss of these cells leads to the most obvious symptoms of Parkinson’s: tremors and trouble walking and speaking. 

Medications called dopamine agonists are often used as therapies for Parkinson’s disease by increasing dopamine levels in the brain. 

But dopamine does a lot more than make us move. It’s also involved in neural signals for memory, attention, mood, personality and cognition, to name a few.

So drugs that improve Parkinson’s patients’ motor functions can also disrupt their behavior and personalities, and even cause hallucinations.  

Recent research has found that people with Parkinson’s sometimes experience hallucinations even without being dopamine agonist medications.  

Following Robin Williams’s suicide in 2014, a leaked pathologist’s report confirming signs of dementia led to to speculations that hallucinations related to the actor’s three-year battle with Parkinson’s may have been to blame for his death.

Parkinson’s hallucinations are predominantly visual, but can be auditory as well, and tend to worsen as cognition deteriorates. 

‘Visual hallucinations in Parkinson’s disease are frequent and debilitating,’ said study author Dr Dagmar H. Hepp. They’re also poorly understood because it’s difficult to distinguish whether the disease or the drug is responsible for the hallucinations.

Robin Williams was diagnosed with Parkinson's before his suicide in 2014. A pathology report leaked after his death included signs of dementia and hallucinations, which some would speculate lead to his suicide

Robin Williams was diagnosed with Parkinson’s before his suicide in 2014. A pathology report leaked after his death included signs of dementia and hallucinations, which some would speculate lead to his suicide

Most prior studies have looked at patients’ brains during specific tasks, but hallucinations often accompany cognitive decline, which also interferes with Parkinson’s patients’ abilities to perform tasks. 

In this study, published by the Radiological Society of North America, Hepp and his team used magnetic resonance imaging (MRI) to examine the resting states of the brains of patients with Parkinson’s disease and hallucinations compared to those without hallucinations. 

This way, they could examine differences in brain connectivity unrelated to completing tasks. 

The images showed that even while they were not tasked with an activity, the brains of the patients with hallucinations were failing to make connections that would help them make sense of visual information and pay attention to what was going on around them.

The study ‘may offer future markers to predict the occurrence of [visual hallucinations] in patients with [Parkinson’s disease],’ the authors wrote. 

This implies that new areas of disconnection visible in MR images could signal doctors that a Parkinson’s patient was nearing the development of hallucinations.  


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