An event such as sexual assault or a battlefield injury is physically agonizing at the time, but it also can eventually sentence a person to a host of mental symptoms—often vivid flashbacks, anxiety and emotional detachment—known as post-traumatic stress disorder (PTSD). The disorder afflicts 3.4 percent of men and 9.7 percent of women in the U.S., according to research estimates.

Diagnosing PTSD is not necessarily simple. Psychological evaluations for PTSD cannot always easily distinguish it from other mental illnesses, such as depression, or determine if a patient is over- or underreporting the symptoms. Now, a brain- scanning technique called magnetoencephelography (or MEG) could offer the first biological test to help specifically diagnose and treat those with PTSD. In a study published January 20 in Journal of Neural Engineering, MEG correctly identified 97 percent of patients that psychologists previously determined were suffering from PTSD.

MEG, which was developed in the 1960s for military purposes, offers a unique insight into the neural communications within the brain, says Apostolos Georgopoulos, a neuroscientist at the University of Minnesota Medical School and lead author of the study. The instrument measures the magnetic field created as electrical current passes between areas of the brain. In MEG studies about two years ago, Georgopoulos found that, whereas healthy people shared similar patterns of neural communication, people with Alzheimer's and schizophrenia had distinct, disease-specific patterns.

In the current study Georgopoulos and his colleagues scanned 74 people diagnosed with various degrees of PTSD through a standard question-and-answer session with psychologists, along with 250 people who reported having no mental problems. For their MEG scans, the participants simply sat under a dome-shaped instrument for one minute. They fixed their eyes on a spot of light so that researchers could measure the brain in an "idle" state, when it is not stimulated by having a task to perform. During that minute, the instrument captured a map of the brain's electrical activity once every millisecond. (For comparison, functional magnetic resonance imaging, which measures brain activity indirectly, takes measurements about every three seconds.)

For 72 of the 74 patients previously diagnosed with PTSD, MEG scans detected a pattern of neural communications that was different from the healthy participants, but shared among the PTSD group. On the flip side, 31 of the 250 healthy patients had abnormal scan results.

"I think [the specificity] is what still has us shaking our heads in disbelief," says Brian Engdahl, a psychologist at the U.S. Department of Veterans Affairs Medical Center in Minneapolis, who helped evaluate the patients included in the study. He adds that he and others hope to perform a more thorough evaluation to see if those 31 supposedly healthy patients might have PTSD.

Engdahl adds that MEG might serve several uses in addition to diagnosis. For one, neural patterns detected by MEG could be used to assess how well PTSD treatments, from antidepressants and sleep medications to counseling, are working for a patient. In addition, having MEG results could help patients who are reluctant to report their PTSD symptoms. "You can think about it as a means to help people feel less stigma. Because there's something different with [the] brain…it doesn't have to do with personal weakness," he says. "That's almost a sigh-of-relief moment for the patient."

Bringing MEG to patients will not, however, be possible for many hospitals in the U.S. Georgopoulos estimates that only 20 to 30 have a $2-million MEG instrument. "[But] I think it will become a major application as we speak…for all kinds of ways of looking very sensitively at brain function," he says.

Rajendra Morey
, a psychiatrist at the Duke–U.N.C. Brain Imaging and Analysis Center in Durham, N.C., who was not involved in the study, says that he could see MEG being used "as an adjunct to the more conventional way of diagnosing." Although a biology-based diagnosis for PTSD would be helpful, he says, using MEG in the clinic is still a ways off.