Robotic system, brain imaging reveal potential source of Parkinson’s disease hallucinations

Reuters Health - 04/05/2021 - A robotic sensorimotor stimulation system combined with brain imaging identified frontotemporal lobe disruptions as the potential source of presence hallucinations in Parkinson's disease (PD).

A presence hallucination conveys a strong feeling of another person being present, mostly to the side or behind the individual who is experiencing the hallucination.

"The association between formed visual hallucinations and a more severe form of PD, with cognitive decline and dementia, is relatively well known," Dr. Fosco Bernasconi of the Ecole Polytechnique Federale de Lausanne (EPFL) told Reuters Health by email, on behalf of himself and two of his coauthors, Dr. Olaf Blanke of EPFL and Dr. Jaime Kulisevsky of the Biomedical Research Institute in Barcelona.

"Presence hallucinations are of particular interest," he said, "because they often occur at an earlier stage of the disease, sometimes even before the motor symptoms, and are believed to anticipate formed visual hallucinations and cognitive decline. Therefore, any early diagnosis of presence hallucination could also help physicians avoid certain treatments."

As reported in Science Translational Medicine, Dr. Bernasconi and colleagues used their robotic-based sensorimotor stimulation system and magnetic resonance imaging to examine presence hallucinations and brain activity in 56 PD patients and 49 controls without PD.

Twenty-six of the PD patients were involved in the initial robotic stimulation study (dubbed a "brain stress test" by the authors) and thirty, comprising an independent cohort, were tested separately.

Analyzing the results of their initial experiments using lesion network mapping of neurological patients without PD, the team was able to link presence hallucinations with disruptions in the frontotemporal lobe.

In the independent PD cohort, the researchers showed that these disruptions were associated with cognitive decline and predicted hallucination severity. They also found that patients with pre-existing presence hallucinations were more sensitive to robotic stimulation than patients with no prior hallucinations.

In a post-experiment debriefing, 38% of PD patients reported that the robot-induced presence hallucinations were comparable or stronger in intensity to the symptomatic hallucinations.

However, some noted differences. For example, one patient said, "It is slightly similar, but it is not exactly the same because the presence (symptomatic) is all of a sudden, while here (the robotic-induced PH) it is built-up."

Dr. Bernasconi said the findings have "several immediate clinical implications. First, destigmatization: patients with PD experiencing hallucinations often do not report them because they fear stigmatization from relatives, friends, and clinicians. Patients may speak more openly to their physicians about them."

"Second, medical awareness: based on the report, clinicians are aware of presence hallucinations and their brain mechanisms," he said, "and should dedicate time to assess the presence of these symptoms."

"Third, scientific explanation: our paper describes the brain mechanisms of presence hallucinations and how they relate to PD," he said. "Clinicians can thus provide affected individuals an explanation."

"Fourth, diagnosis: We hope that in the nearer future, clinicians in hospitals and clinics will be able to employ our 'hallucination stress test' to induce presence hallucinations in safe and controlled conditions and to quantify an individual's hallucination sensitivity," Dr. Bernasconi concluded.

Dr. James Beck, chief scientific officer of the Parkinson's Foundation, headquartered in Miami, commented in an email to Reuters Health, "The ability to repeatedly simulate presence hallucinations will be very valuable to better understand the biological basis of these phenomena."

"More importantly for people with PD, it can potentially provide a platform by which to develop new medications and treatments for hallucinations," he said. "It is hard to study something if you have to wait for it to happen."

"While the ability to simulate this type of hallucinations is potentially useful, it is not a complete simulation," he added. "It was telling to have the participant quotes that demonstrates the richness of a true presence hallucination versus the simulated version."

"This is a novel research tool," Dr. Beck noted, "(but it) will not replace the role of a clinician simply asking their patients whether they are experiencing hallucinations, (which) can often be treated by adjustment of current medications or prescribing PD-specific antipsychotics."

SOURCE: https://bit.ly/33ds1uS Science Translational Medicine, online April 28, 2021.

By Marilynn Larkin



Posted on 4 May 202124 May 2021