For all the attention focused on posttraumatic stress disorder (PTSD) in recent years, doctors have never had a clear-cut way to be certain a patient has it. But Minnesota scientists now believe they have found a long-sought PTSD fingerprint that confirms the disorder by measuring electromagnetic fields in the brain. The finding, detailed in the latest issue of the Journal of Neural Engineering, could help the 300,000 cases of PTSD that are anticipated among the 2 million U.S. troops who have gone to war in Afghanistan and Iraq.

"This shows that PTSD is a brain disease," says Dr. Apostolos Georgopoulos, who led the research along with Brian Engdahl and a team from the Brain Sciences Center at the Minneapolis VA Medical Center and University of Minnesota. "There have been questions that this is a made-up disorder and isn't a true brain disease, but it is." Just as importantly, he says, the magnetic-imaging biomarker shows changes over time in a brain's electrical activity, allowing mental-health workers to chart the effectiveness of various therapies. "It will be a tremendous tool in monitoring treatment," he says, "because these abnormal communication patterns will be normalized as the treatment works." (See pictures of an Army town coping with PTSD.)

Up until now, more conventional diagnostic tools, including computed tomography, magnetic-resonance imaging and X-rays have not been able to detect evidence of PTSD because their snapshots of brain activity occur too slowly. The new diagnostic procedure uses magnetoencephalography (MEG), a way of monitoring the flow of electrical signals along the brain's neural pathways from cell to cell. By using a helmet with 248 noninvasive sensors arrayed around the head, scientists can map patterns of electrical activity inside the skull and detect abnormalities. The Minnesota researchers used MEG to assess 74 U.S. veterans believed to be suffering from PTSD, along with 250 subjects not thought to be suffering from the condition. Distinctive brain patterns indicating PTSD were found in 72 — or 97.3% — of the 74 people diagnosed with PTSD through the traditional interview process; false positives turned up in 31 of the 250 subjects (12.4%) without PTSD. (All the subjects were given "a simple fixation task ... to engage the brain in a stable condition.")

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