Neuroimaging in practice

This was the question that Dr Philip McGuire from the United Kingdom addressed in his talk at ECNP 2015 on using neuroimaging to predict outcomes in psychosis. In the context of bipolar I disorder, this is of particular interest given the often significantly delayed diagnosis due to the complex clinical presentation of the illness.

“When we look at people at high risk of psychosis before they have had an episode, it isn’t possible to predict whether their symptoms will develop into psychosis. Typically one-third will develop a psychosis in three years, another third will have persistent symptoms and the remainder will recover,” said Dr McGuire. “Preventative intervention in all those at risk is inefficient and raises ethical issues. Biomarkers that predict outcomes would allow us to tailor treatment according to the likely outcome.”

Medial temporal

In a study looking at longitudinal reduction in the medial temporal volume¹, it was apparent that the hippocampus seemed to be larger in the subgroup that later became psychotic: “There was an increase in activity in the hippocampus as individuals became psychotic and the onset of psychosis was associated with an elevated dopamine function,” said Dr McGuire.

Given that one in three patients will not respond to conventional antipsychotics, Dr McGuire argued that biomarkers could permit earlier treatment with other interventions.

Dopamine and glutamate

Dr McGuire then turned to studies that showed dopamine function to be different for those who do well on antipsychotics; in fact it seemed normal in the group who didn’t respond well to the medication.^2,3 Patients who responded poorly to antipsychotics also had an elevation in the glutamate.⁴

But one has to be cautious when interpreting these studies, warned Dr McGuire, because they didn’t follow participants before starting treatment.  This is being addressed in a new Finnish study due to conclude in 2016; Dr McGuire is hopeful it will confirm previous findings.

PSYSCAN

There are a number of multi-centre imaging studies in the pipeline to help provide samples large enough to assess predictive power. One such study is PSYSCAN (led by King’s College London-Institute of Psychiatry (United Kingdom) which is due to deliver results around 2020. PSYSCAN aims to establish a method of analysis of images of the central nervous system obtained by magnetic resonance imaging, which allows patients with psychosis to be classified. The hope is this will enable implementation of more specific pharmacological and psychotherapeutic treatment criteria.

“The idea is to make a tool that people can use in the clinic such as is happening at Cambridge Cognition with their neuropsychological computerized tests for cognition in the field of dementia,” said Dr McGuire.

The future is neuroimaging?

Reflecting on where we are today and the future, Dr McGuire concluded: “Research has demonstrated that there are neuroimaging differences between subgroups of patients with distinct clinical outcomes. Two of the most promising applications are in the prediction of onset of psychosis in people at high risk and response to treatment in psychosis. The time seems to have arrived where neuroimaging may not only be an important research tool, but may actually aid the clinician in the diagnosis and treatment of psychosis.”

Watch this space…..