"The biggest finding is how these MCS patients' brains respond to pain in a way very similar to your and my brain and how very different this is from what we saw in persistent vegetative state (PVS) patients, even if at the bedside the clinical examination of these MCS and PVS patients is very, very similar," senior author Dr. Steven Laureys told Reuters Health.
Dr. Laureys, a researcher with the University of Liege in Belgium, said that his team's study is the first to use PET "to directly measure the brain's response to potentially painful stimuli ... in MCS patients who, by definition, cannot tell us if it hurts."
The study, reported in the October 6 online issue of the Lancet Neurology, included five patients in MCS, 15 in PVS, and 15 healthy controls. The brain response to bilateral electrical stimulation of the median nerve was assessed with oxygen-15-radiolabeled water PET. In addition, a psychophysiological interaction analysis was performed to evaluate the functional connectivity of the primary somatosensory cortex.
In both MCS patients and in controls, noxious stimuli caused activation of the thalamus and other brain structures known to make up the cortical pain matrix. Moreover, the degree of activation in each area was comparable for the two groups.
PVS patients, by contrast, showed much less activation in these brain areas. The authors also found that functional connectivity with the cortical network, which includes the frontoparietal associative cortices, was preserved in MCS patients, but not in PVS patients.
"In my view, our scanning results should be interpreted as strong evidence in favor of preserved perception of pain and hence should prompt clinicians to use painkillers even if patients cannot tell us they feel pain," Dr. Laureys said.
In an accompanying editorial, Dr. John Whyte, from Moss Rehabilitation Research Institute in Elkins Park, PA, comments that "at present, these findings might be useful to help physicians and caregivers interpret and manage pain-related behaviors that are not associated with any known pain generator -- i.e., many patients in PVS and MCS grimace, moan, and show behaviors that are typically interpreted as signs of pain in neurologically intact individuals, despite the absence of any known stimulus."
By Anthony J. Brown, M.D.
Lancet Neurol 2008.
Last Updated: 2008-10-08 12:52:42 -0400 (Reuters Health)
Brain activity may explain 'placebo effect,' August 2, 2007
Copyright © 2008 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.