Minor hallucinations may predict Parkinson’s cognitive decline: Study

Frontal executive function decline more rapid over 5 years for those with early hallucinations

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by Andrea Lobo |

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The early appearance of minor hallucinations in people with Parkinson’s disease might be a predictor of faster cognitive decline, a recent study suggests.

Among those with hallucinations, cognitive decline was also associated with electrical activity in the frontal lobe, a part of the brain that controls cognition.

The study, “Theta oscillations and minor hallucinations in Parkinson’s disease reveal decrease in frontal lobe functions and later cognitive decline,” was published in Nature Mental Health.

Minor hallucinations, like presence hallucinations — the strong sensation of a presence when no one is there — happen often in people with Parkinson’s disease, but are underreported, either ignored by patients and clinicians or considered a side effect of medication.

“We now know that early hallucinations are to be taken seriously in Parkinson’s disease,” Olaf Blanke, MD, PhD, Bertarelli chair in cognitive neuroprosthetics, and lead of EPFL’s Laboratory of Cognitive Neuroscience, said in a press release

“If you have Parkinson’s disease and experience hallucinations, even minor ones, then you should share this information with your doctor as soon as possible,” said Fosco Bernasconi, PhD, the lead author of the study.

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Hallucinations and cognitive decline

Parkinson’s disease causes motor symptoms, such as tremors, muscle rigidity, and slowness of movements, and can also cause nonmotor symptoms, including cognitive impairment, depression, hallucinations, and sleep problems.

Hallucinations are not much known about as a symptom of Parkinson’s, but are highly prevalent in the disease course — one of two patients has them regularly. A third of Parkinson’s patients have early hallucinations before motor symptoms appear.

They can start as minor signs such as presence hallucinations, usually occurring early in the disease, and progress to more severe hallucinations. Complex visual hallucinations — seeing someone who isn’t there — can occur at later stages of the disease.

Minor hallucinations have been suggested to predict cognitive decline in Parkinson’s disease, but this hasn’t been well established by clinical research, leading researchers at the École Polytechnique Fédérale de Lausanne (EPFL) and the Sant Pau Hospital in Barcelona to look for early symptoms, particularly minor hallucinations, to aid in developing strategies to slow the progression of cognitive and psychiatric symptoms with Parkinson’s disease.

“Detecting the earliest signs of dementia means early management of the disease, allowing us to develop improved and personalized therapies that try to modify the course of the disease and improve cognitive function,” Blanke said.

The study included 75 people between the ages of 60 and 70 with Parkinson’s disease. Interviews were done to assess patients’ cognitive condition and to see whether they were having hallucinations, along with electroencephalogram (EEG) measurements to assess their brain’s activity at rest.

An EEG is a widely available, noninvasive way to record the brain’s electrical activity and is measured as brainwaves (oscillations) with different frequencies, a result of electrical pulses from nerve cells communicating with each other.

Parkinson’s patients with early hallucinations saw a more rapid decline in frontal executive function over the following five years. This decline was connected to the presence of frontal theta (4-8Hz) waves, as measured by EEG during the initial visit. This link was only observed in those with hallucinations at the onset of the disease, however.

“We aim to have an early marker to identify individuals at risk of a more severe form of Parkinson’s disease, characterized by a more rapid cognitive decline and dementia, based on hallucinations proneness. And ideally identify those individuals even before hallucinations actually occur. We are therefore developing neurotechnology methods and procedures for that purpose,” Bernasconi said.