Psychogenic diseases, formerly known as ‘hysterical’ illnesses, may look very similar to genetic diseases of the nervous system or to illnesses caused by damage to the nerves, brain or muscles. They can result in many severe symptoms, such as painful cramps or paralysis.
However, unlike organic diseases, psychogenic diseases do not have any apparent physical cause, making them difficult to diagnose and even more difficult to treat.
This study looked at people with either psychogenic or organic dystonia (a movement disorder in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures), as well as healthy people with no dystonia.
Both types of dystonia caused painful and disabling muscle contractions affecting the leg.
Understanding these disorders, diagnosing them early and finding the right treatment are all clearly very important. We are hopeful that these results might help doctors and patients understand the mechanism leading to this disorder, and guide better treatments.
Dr Anette Schrag, UCL Institute of Neurology
The organic patient group had a gene mutation (the DYT1 gene) that caused their dystonia. The psychogenic patients had the symptoms of dystonia but did not have any physical explanation for the disease, even after extensive investigations.
The scientists performed PET brain scans on the volunteers at UCL to measure the blood flow and brain activity of both dystonia groups and the healthy volunteers. The participants were scanned with three different foot positions: resting, moving their foot, and holding their leg in a dystonic position. The electrical activity of the leg muscles was measured at the same time to determine which muscles were engaged during the scans.
The researchers found that the brain function of individuals with the psychogenic illness was very different to the brain function of individuals with the organic (genetic) disease.
First author Dr Anette Schrag, from the UCL Institute of Neurology, says: “Finding abnormalities of brain function that are very different from those in the organic form of dystonia opens up a way for researchers to learn how psychological factors can, by changing brain function, lead to physical problems.”
Dr James Rowe, University of Cambridge, added: “What struck me was just how very different the abnormal brain function was in patients with the genetic and the psychogenic dystonia. Even more striking was that the differences were there all the time, whether the patients were resting or trying to move.”
In addition, the researchers found that one part of the brain (the prefrontal cortex) previously associated with psychogenic disease is an unreliable indicator. Abnormal activity in this region is not unique to psychogenic disease and the same pattern of activity was also observed in patients with organic dystonia when they tried to move their feet.
Dr Arpan Mehta, from the University of Cambridge, says: “It is interesting that, despite the differences, both types of patient had one thing in common – a problem at the front of the brain. This area controls attention to our movements and although the abnormality is not unique to psychogenic dystonia, it is part of the problem.”
This type of illness is very common, as Dr Schrag explains: “One in six patients that see a neurologist has a psychogenic illness. They are as ill as someone with organic disease, but with a different cause and different treatment needs. Understanding these disorders, diagnosing them early and finding the right treatment are all clearly very important. We are hopeful that these results might help doctors and patients understand the mechanism leading to this disorder, and guide better treatments.”
The research was published today in the journal Brain.
Media contact: David Weston