Using brain imaging called functional MRI, he and his colleagues found that three women with conversion disorder showed an unusual pattern of brain activity related to their symptoms.

All of the women had sensory conversion disorder, which involves a loss of sensation in a limb. Each had numbness in one hand or foot that could not be traced to any physical problem.

Normally, when a healthy limb is touched, a particular, sensation-related area of the brain on the side opposite to that limb will be activated. For the three women in Feinstein's study, stimulation of the numb limb failed to trigger activity in this sensory area of the brain. Instead, brain regions involved in emotion "lit up" on the MRI scans.

Next, the researchers stimulated both the affected and unaffected limb at the same time. This time, the sensory-related areas on both sides of the brain were activated. But so too were the same emotional regions, and the women still felt numbness in the affected limb, Feinstein said.

"What these data show are that very clear brain changes are driving hysteria," he told Reuters Health.

The fact that emotional structures in the brain were activated by touch supports the general belief about conversion disorder -- that a psychological trauma or stress is at the root of the physical symptoms. For some people, the distress becomes connected to numbness in a limb, for others it's a problem with movement or memory.

It seems the trauma essentially "overwhelms" the brain's normal functioning, Feinstein said. Inappropriate activity in the brain's emotional structures may inhibit normal activity in areas related to sensation and movement.

Feinstein and his colleagues are now studying whether sensory problems can be improved by distracting patients' attention during limb stimulation. That is, can the brain be "fooled" into a normal pattern of activation?

Feinstein said it's unclear whether the research will yield any new therapies for conversion disorder, which is typically addressed by treating the anxiety or other psychiatric problem believed to be behind the symptoms.

Meanwhile, for people who may have had their symptoms dismissed by a doctor, or who believe that they're just "crazy," Feinstein noted, this brain research shows that "a very real process" is behind their problems.

SOURCE: Neurology, December 12, 2006.

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