Dec 12 2006
Hysteria is an unexplained neurological disorder in which a patient complains of symptoms, ranging from numbness in a limb, to paralysis, memory loss and seizures, that cannot be traced to any known medical problem and doctors fail to find anything medically wrong with them.
Hysteria is also termed as 'sensory conversion disorder' and the new study promises to reveal a better understanding of the condition.
It was Freud himself who said conversion disorder is so named because it's thought that people 'convert' a psychological distress into a physical symptom which is not under their conscious control and the new study validates that Freudian view.
The research team examined three women with sensory conversion disorder who had complained of numbness in their left hand or foot.
The researchers used brain imaging called functional MRI to study how the brains of these three women responded to stimulation of their numb body parts.
In all three cases, the study found stimulation of the numb hand or foot failed to activate the side of the brain which responds to touch.
However, it was found that when researchers stimulated both the numb body part and the normal feeling hand or foot, the brain did respond.
As a rule 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 the 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.
The study's author Omar Ghaffar, MD, MSc, of Sunnybrook Health Sciences Centre in Toronto, Ontario, says the discovery is new and may help explain the differing results in the few studies devoted to the topic.
Ghaffar suggests that bilateral stimulation acts as a distraction, shifting the patient's attention, and thereby overcoming the inhibition.
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, and inappropriate activity in the brain's emotional structures may inhibit normal activity in areas related to sensation and movement.
Dr. Ghaffar says future studies aim to build on the findings by scanning more subjects and healthy controls.
He says a study examining the role of distraction in conversion disorder is already underway but it is unclear whether the research will suggest any new therapies for the disorder, which is usually treated as an anxiety or other psychiatric problem.
The researchers say for people who may have had their symptoms dismissed by a doctor, or who believe that they're just "crazy," the research shows that "a very real process" is behind their problems.
The study is published in the current issue of Neurology, the scientific journal of the American Academy of Neurology.
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