Monday, 3 August 2009

Inside the brain of a woman with conversion paralysis

A new brain imaging study shows the difference, in terms of brain activity, between a person feigning having a paralysed arm and a patient with conversion paralysis - that is, paralysis with no clinically identifiable neurological cause.

Conversion paralysis is one manifestation of conversion disorder, previously known as hysteria, which was made famous by the nineteenth century French neurologist Jean-Martin Charcot (pictured) and later, by his students Pierre Janet and Sigmund Freud. The label "conversion" disorder comes from the idea that an emotional complaint is somehow converted into a physical symptom.

In the current study, Yann Cojan and colleagues scanned the brain of a 36-year-old woman with conversion paralysis, as she completed a version of the Go / No Go task. Trials began with a signal telling her which hand to respond with, followed, after a delay, by a green or red signal (Go / No Go), which indicated whether the response should be made or withheld (it was green on 75 per cent of trials).

The woman, divorced with two children, had recently recovered from a physical illness and had suffered a stressful relationship break up. Her complaint was of paralysis in her left hand, despite no identifiable neurological cause. The woman's brain activity during the task was compared with that of several healthy controls, a minority of whom were asked to feign having paralysis in their left hand.

As expected, the researchers found suppressed activity in the right primary motor cortex of the female patient when she attempted to move her "paralysed" hand (you'll remember that the right hemisphere controls the left side of the body). A similar suppression was observed in the controls who were feigning paralysis.

However, unlike in the controls, the researchers also observed in the patient's brain increased connectivity between the right motor cortex and midline structures, including the ventromedial prefrontal cortex and the precuneus, which is found in the parietal lobe. These brain regions have previously been associated with self-monitoring, mental imagery and autobiographical memory, thus raising the intriguing possibility that this anomalous activity could represent the brain basis for emotional interference with motor control.

Two other key findings emerged. The brain region normally associated with consciously inhibiting a prepared response - the inferior frontal gyrus - was not activated when the woman failed to move her "paralysed" hand (but it was activated when the controls feigned paralysis on "Go" trials). Moreover, there was evidence of preparatory motor activity in the woman's brain during Go trials with her "paralysed" hand, thus supporting her claim to be willing a movement to occur.

"Taken together, our results may help better understand the brain pathways by which self-awareness becomes distorted in these patients [with conversion disorder] and how the mind may take control over the body during conversion," the researchers said.
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ResearchBlogging.orgCojan, Y., Waber, L., Carruzzo, A., & Vuilleumier, P. (2009). Motor inhibition in hysterical conversion paralysis. NeuroImage, 47 (3), 1026-1037 DOI: 10.1016/j.neuroimage.2009.05.023

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

2 comments:

  1. Danielle5:36 pm

    I don't know how often you check this but wanted to write anyway. I have conversion paralysis... what a terrifying, debilitating condition! Following a year of significant distress I began to experience paralysis on my right side only. I was tested extensively but nothing was found. I was diagnosed at that time with hemiplegic migraines. My right side was periodically affected for a year. My life circumstances became even MORE stressful and I experienced my 1st full-body episode on February 19th of this year. I would love to communicated with you or others that also suffer from conversion paralysis. Thanks so much for your site and for 'listening.'

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    1. Anonymous11:53 pm

      Hi Danielle. My 11 year old son has conversion paralysis, whole body or just parts, including deafness, blindness, inability to speak. It's hard to find any information or support for this condition, and it's very scary for him (and us). Currently he is having a lot of collapses but they are only lasting minutes-1 hour, not days or weeks. The hospital can't tell us how long it will last or anything. Sympathise with you!

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