MRI imaging could aid in identifying patients with psychosis

Researchers believe a certain type of magnetic resonance imaging—neuromelanin-sensitive MRI—can detect a potential biomarker for identifying psychosis.

Studies conducted at the National Institute of Mental Health, which is part of the National Institutes of Health, have found that the NM-MRI signal detects a marker of dopamine function in persons with schizophrenia and also serves as an indicator of the severity of psychotic symptoms. Dopamine is a chemical messenger that carries signals between brain cells.

“Disturbances affecting the neurotransmitter dopamine are associated with a host of mental and neurological disorders, such as schizophrenia and Parkinson’s disease,” says Joshua Gordon, MD, director of NIMH. “Because of the role dopamine plays in these disorders, the ability to measure dopamine activity is critical for furthering our understanding of these disorders, including how to best diagnose and treat them.”

Despite the potential for NM-MRI to detect a biomarker, it has not yet been shown to actually provide a marker of dopamine function, nor has its utility been demonstrated in persons without neurodegenerative illness.

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In the research done at Columbia University, Guillermo Horga, MD, along with colleagues, showed that NM-MRI can serve as a marker of dopamine function in individuals without neurodegenerative disorders. Importantly, NM-MRI does not involve radiation or invasive procedures, Horga adds. This makes it more suitable for pediatric patients and for repeated scanning, which could ease monitoring progression of illness or response to treatment.

“It only takes a short scan that could be implemented in most clinical scanners,” Horga notes. “It also affords a very high anatomical resolution compared with PET measures, which is important to examine functions or dysfunctions of specific parts of the substantia nigra.”

This is a structure in the midbrain that plays a role in reward and movement.

In the course of the study, researchers used NM-MRI data from patients with Parkinson’s disease and patients without the disease. They found decreases in NM-MRI signals in those with Parkinson’s in the lateral, posterior and ventral regions of the substantia nigra that corresponded to the known anatomical distribution of cell loss in this brain area in Parkinson’s disease. The results confirm that NM-MRI can capture known topographical variability within this part of the brain structure.

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Researchers then looked at the link between MN-MRI signal and the severity of psychosis, finding that more severe symptoms of psychosis were associated with higher NM-MRI signals in the nigrostriatal pathway (movement) of persons with schizophrenia and those at risk for schizophrenia.

“We are now extending this work to see if we can detect abnormalities in neuromelanin signal (a pigment) that help us predict which individuals are more likely to develop a psychotic disorder among those who already show early symptoms of psychosis,” Horga concludes. “We are also interested in exploring whether neuromelanin-sensitive MRI could be used in the future to determine who might best benefit from dopaminergic treatments.”

The full study is available in the Proceedings of the National Academy of Science.

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