A brain disorder is charted on MR coincidence maps
Caren B. Les
Researchers have used MRI to show structural and functional abnormalities in specific brain areas of schizophrenic patients who persistently experience auditory hallucinations. These anomalies appear jointly in brain regions that regulate emotions and process human voices.
The findings could improve the diagnosis, evaluation and treatment of schizophrenia. The chronic brain disorder affects approximately 1 percent of the population. Those afflicted may experience hallucinations, paranoia, delusional thoughts and disorganized thinking. The disease is thought to result from genetic and environmental factors. Although there is no known cure, it is treatable with drugs and psychotherapy.
Scientists have used MRI to find abnormalities in specific regions of the brain in schizophrenic patients. Increased activation associated with emotional auditory stimuli and decreased gray matter volume are highlighted in these functional MR coincidence maps of the brain. The yellow areas show greater values for functional and morphometric statistical source images. Reprinted with permission of Radiology.
Many brain abnormalities have been implicated in schizophrenia by means of MRI, but no single region has been consistently reported to be abnormal, according to Dr. Luis Martì-Bonmatì, who led the team at the Dr. Peset University Hospital in Valencia, Spain. The differences in clinical manifestations and the methods of acquiring and processing images among studies may explain the resulting inconsistencies, he added.
Testing brain response
The investigators conducted their study on 31 right-handed men — 21 with schizophrenia who suffered from chronic auditory hallucinations and 10 healthy control subjects. They acquired both morphological and functional MR images with an Intera 1.5-T scanner from Philips Medical Systems of Best, the Netherlands. Because language impairment is one of the core characteristics of the disease, they used auditory stimulation.
To gauge brain response to auditory stimuli, the researchers submitted all subjects to both a functional MRI session during which they heard words with high emotional content, and a session in which they heard words with neutral emotional content. A dynamic echo-planar T2-weighted functional MR sequence was obtained in each session.
To show structural analysis of the brain, a high spatial resolution 3-D spoiled gradient-echo T1-weighted MR sequence was acquired after the functional MR examinations.
The researchers analyzed the images using parametric mapping software. They extracted the brain activation images by subtracting images captured when emotional words were heard from images captured when nonemotional words were heard. They used voxel-based morphometry to explore anatomical differences and overlaid the functional and structural MR images to show only the voxels statistically reported by both techniques.
Analytical maps showing coinciding regions of functional and structural brain abnormalities were generated. Martì-Bonmatì said that they were surprised to see so many coinciding areas and that those areas follow the same pattern of reduction of volume and overreaction to emotion. He said that a neurophysiological interaction among psychopathology (the auditory hallucinations), brain function (increased hemodynamic response in the temporal lobe) and structure (deficits in gray matter) seems to exist.
Martì-Bonmatì suggested that the findings could open up the use of MR coincidence maps for specific diagnosis and follow-up of schizophrenic patients after treatment.
“If we can demonstrate that the coincidence areas are modified by disease severity and response to treatment, we will have a suitable tool to monitor the disease,” he said.
Radiology, August 2007, pp. 549-556.
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