Wednesday, February 27, 2013

People in a vegetative state may feel pain - health - 23 February 2013 - New Scientist

It is a nightmare situation. A person diagnosed as being in a vegetative state has an operation without anaesthetic because they cannot feel pain. Except, maybe they can.

Alexandra Markl at the Schön clinic in Bad Aibling, Germany, and colleagues studied people with unresponsive wakefulness syndrome (UWS) – also known as vegetative state – and identified activity in brain areas involved in the emotional aspects of pain. People with UWS can make reflex movements but can't show subjective awareness.

There are two distinct neural networks that work together to create the sensation of pain. The more basic of the two – the sensory-discriminative network – identifies the presence of an unpleasant stimulus. It is the affective network that attaches emotions and subjective feelings to the experience. Crucially, without the activity of the emotional network, your brain detects pain but won't interpret it as unpleasant.

Using PET scans, previous studies have detected activation in the sensory-discriminative network in people with UWS but their findings were consistent with a lack of subjective awareness, the hallmark of the condition.

Now Markl and her colleagues have found evidence of activation in the affective or emotional network too (Brain and

Her team gave moderately painful electric shocks to 30 people with UWS, while scanning their brains using fMRI. Sixteen people had some kind of brain activation – seven only in the sensory network but nine in the affective network as well.

These results question whether some diagnoses should change from UWS to minimally conscious, which is characterised by some level of awareness.

"I don't think this paper alone will change the clinical approach to people with diagnoses such as UWS," says Donald Weaver at Dalhousie University in Halifax, Nova Scotia, Canada, who was not involved in the work. But it will encourage future study, he says.

Changing a diagnosis depends on whether neurologists are ready to accept alternative ways of diagnosing disorders of consciousness, says Boris Kotchoubey at the Institute of Medical Psychology and Behavioural Neurobiology in Tübingen, Germany, who worked on the study.

Nonetheless, Kotchoubey is confident that the way people with UWS are cared for will change, even if their diagnoses remain the same. "I know that many doctors working with such patients have been instructed to treat their patients as if they can understand them and perceive at least something in the environment, perhaps pain, pleasure, or emotion," he says.

But not all people are treated this way. Prior to the study, one of the people in Markl's study was given no anaesthesia before a tracheotomy, which involves an incision in the neck to allow breathing without using the nose or mouth. As people with UWS are clinically considered unable to understand pain, doctors do not have to give an anaesthetic.