EEG May Help Diagnose Schizophrenia, Improve Treatment

Deborah Brauser

November 06, 2014

Electroencephalography (EEG) may help diagnose patients at risk for psychosis and even help determine the best treatment options for the disorder, two new studies suggest.

Dr Gregory Light

The first study, which was published online October 23 in Schizophrenia Research and included nearly 1800 participants, showed that those with schizophrenia had impaired auditory processing and registered subtle sound changes at a significantly lower rate than their healthy peers without the disorder, which was clearly evident in EEG brain activity patterns.

The second study, published in the October issue of NeuroImage: Clinical, showed that results of EEG testing were linked to "patients' cognitive and psychosocial impairments."

This suggests the test could be used to objectively measure condition severity, note the investigators in a release. Conversely, investigators add that "it might be possible to alleviate some of the symptoms of schizophrenia with specialized cognitive exercises designed to strengthen auditory processing."

Gregory A. Light, PhD, coauthor of both studies and associate professor of psychiatry at the University of California, San Diego (UCSD), told Medscape Medical News that the overall findings suggest that simple EEG testing can now be brought into the clinical setting to help this patient population.

"We've been working for many years on validating laboratory-based tests that measure the functioning of the auditory processing network, in essence to take the guesswork out of a diagnosis in an objective, reliable way," said Dr Light, who is also associate director of the Mental Illness Research, Education, and Clinical Center in the VA San Diego Healthcare System.

Promising Biomarkers

Previous studies by the investigators and others have shown that sensory processing impairment contributes to much of the dysfunction found in patients with schizophrenia, and that mismatch negativity (MMN) may be promising as a quantitative clinical biomarker, Dr Light noted.

"Patients with schizophrenia have problems in how they process auditory information, which is manifested through auditory hallucinations and cognitive impairment that relies on auditory input," he said.

"The brain system that is responsible for these hallucinations is the same network that is implicated in auditory attention, auditory working memory, verbal memory, and many other cognitive domains."

In the first study, 1790 adults (966 of whom had schizophrenia) were enrolled at five sites in the United States: UCSD; the University of California, Los Angeles; the University of Washington, in Seattle; the University of Pennsylvania, in Philadelphia; and Mount Sinai School of Medicine, in New York City.

Brain activity patterns were measured while all participants listened to a sequence of short beeps and intermittent longer pings.

Results showed that the group with schizophrenia had reduced MMN (which measured brain response differences between the expected short beeps and the different, longer ping) in comparison with the healthy controls group.

The schizophrenia group also had significantly reduced P3a, a measure of electrical brain energy, as attention automatically shifted to the longer ping.

"This suggests that they had a muted ability to detect and direct their attention to the discordant beep," said the investigators.

Age, sex, and race accounted for 26% of the MMN variance (P < .001) and 18% of the P3a variance (P < .001). For both measures being older, male, or black or having schizophrenia all predicted significantly smaller amplitudes.

Secondary analysis within just the group with schizophrenia showed that taking first-generation antipsychotics or a combination of both first- and second-generation antipsychotics predicted significantly smaller MMN amplitudes vs taking no medication (P = .035 and P = .001, respectively). However, those taking just second-generation antipsychotics did not differ significantly from those taking no medication.

When measuring P3a, taking first-generation, second-generation, and a combination of both types of antipsychotics all predicted less amplitudes (P = .002, P < .001, and P = .001; respectively).

Finally, taking anticholinergic medications was associated with significantly smaller MMN amplitudes (P < .001) but not P3a amplitudes.

The investigators note that although past research has shown that both MMN and P3a are "promising biomarkers for understanding and treating psychotic disorders," this study showed the feasibility of using them in a multisite trial.

"We found that a relatively simple, 2-channel system yielded 91% usable…data in less than 30 minutes," they write.

Predictor of Symptom Severity

In the second study, 42 adult patients with schizophrenia (63% men; mean age, 45 years) and 47 participants without any psychiatric disorder (45% men; mean age, 43 years) were assessed.

Results showed that "measures of MMN and P3a were associated with the severity of a patient's symptoms and their day-to-day real-world functioning," reported the researchers.

In fact, differences in MMN and P3a "auditory processing metrics accounted for approximately half of the variance in the severity of patients' symptoms," the investigators said in a release.

"We think it may be possible to train some patients' auditory circuits to function better. This could improve their quality of life, and possibly reduce common symptoms of schizophrenia, such as hearing voices," said Dr Light.

The investigators add that the overall results from both studies show that MMN and P3a can be measured effectively with just a couple of EEG electrodes placed on the scalp ― which means EEG testing is ready to leave research laboratories and be used in the real world.

In fact, the investigators are now planning to use these tests on patients at Alpine Special Treatment Center, a community mental health facility in San Diego. They hope to be able to improve patients' brain function through daily cognitive exercises "designed to sharpen their sensory information processing."

"We will then use EEGs to see if we can identify markers that predict which patients are most likely to benefit from this form of treatment," added Dr Light.

He noted that a growing body of research suggests "we can use neuroscience-based biomarkers that are reliable and valid to both improve our understanding of psychosis, to perhaps select patients for early intervention, and maybe even to monitor changes across illness."

Although he added that the tests might not be able to differentiate between schizophrenia and bipolar disorder, they should be useful for helping to identify those at risk for psychosis in general.

"This is a very exciting time. We are turning the corner on our understanding of brain disorders and treatments," concluded Dr Light.

The study authors have reported several financial relationships, which are fully listed in the original articles.

Schizophr Res. Published online October 23, 2014. Abstract

Neuroimage Clin. 2014;6:424-437. Full article

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