Diffusion tensor imaging charts path to schizophrenia

Using diffusion tensor imaging, California researchers have confirmed that the brain's white matter in subjects at risk for schizophrenia develops differently compared with that in healthy people. DTI scans of white matter integrity can also predict functional decline.

Neuroimagers know that people with schizophrenia undergo white matter disruption. Multiple studies have also identified the left frontal and temporal lobes as the brain regions where white matter reduction most consistently correlates with the condition. But researchers do not know exactly how or when this change happens. According to principal investigator Katherine Karlsgodt, Ph.D., a fellow in the University of California, Los Angeles psychology department, DTI can provide some clues.

“We found that healthy subjects showed a normal and expected increase in measures indexing white matter integrity in the temporal lobe as they age,” said Karlsgodt, “but young people at high risk for psychosis showed no such increase. That is, they fail to show the normal developmental pattern,” she said.

Karlsgodt and colleagues at UCLA's Semel Institute for Neuroscience and Human Behavior assessed 36 teens and young adults at high risk for developing schizophrenia and 25 healthy subjects as the control group. Both groups underwent baseline DTI in addition to clinical and functional evaluations and periodic follow-up over a two-year period.

Investigators found that, in addition to showing that white matter in the brains of the at-risk group did not develop at the same rate as it did in healthy subjects, DTI scans could also be used to predict whether subjects at risk for schizophrenia would suffer further neurological decay. Findings appeared in the May 6 online edition of Biological Psychiatry.

“This is a very exciting finding, because it means we might be closer to being able to identify people who will need more or different treatments in the future, so that we can get them the help they need,” Karlsgodt said.

More than three million people in the U.S. suffer from schizophrenia, according to the National Institute of Mental Health. The auditory hallucinations and paranoia that characterize the condition often appear during late adolescence or early adulthood. Though incurable, the condition's chronic and impairing symptoms can be treated. More research is needed, however, to enhance diagnosis and treatment of the psychosis and mitigate its social and economic impact.

Failing to find a normal increase in white matter integrity over time in the at-risk subjects suggests there is a fundamental difference in how at-risk adolescents and young adults develop right before disease symptoms become evident, Karlsgodt said.

“Something may go awry with the developmental process during this period that might contribute to the onset of the disorder,” she said.

Karlsgodt and her colleagues are members of the Center for the Assessment and Prevention of Prodromal States at the Semel Institute. The center provides clinical and neurological assessment and treatment for patients with psychological and psychiatric needs. It conducts ongoing research aimed at early diagnosis, prevention, and understanding of neurological disorders.