A study of brain activity in brain-damaged patients in a minimally conscious state (MCS) suggests that they could have similar pain perception to healthy people. Thus, these patients could need painkilling treatment. The findings are reported in an Article published early Online and in the November edition of Lancet Neurology, written by Dr Steven Laureys, Coma Science Group, Cyclotron Research Center and Department of Neurology, University of Liege, Belgium, and colleagues.
A persistent vegetative state (PVS) is defined by wakefulness without awareness of self or the environment whereas MCS patients show some evidence of self and environmental awareness. However, carers of MCS patients have difficulty assessing the levels of conscious pain through the patients' behaviour. The researchers compared brain activity following electrical stimulation of the median nerve in five MCS patients (aged 18-74 years) with 15 controls (aged 19-64) years and 15 PVS patients (aged 18-75 years). They looked at the areas of the brain responsible for pain sensation (the cortical pain matrix), including the thalamus, the primary somatosensory cortex and the insular, frontoparietal and anterior cingulate cortices.
The researchers found that none of these areas of the brain was less activated in MCS patients than in controls, and in MCS patients the cortical pain matrix was significantly more active than in PVS patients. MCS patients also showed better 'connectivity' between different brain regions responsible for pain than did PVS patients. The authors conclude: "These findings might be objective evidence of a potential pain perception capacity in patients in MCS, which supports the idea that these patients need painkilling treatment."
In an accompanying Comment, Dr John Whyte, Moss Rehabilitation Research Institute, Elkins Park, Pennsylvania, USA, says: "Increased understanding of the neural processing that can ake place in the absence of the conscious awareness, and the patterns of neural activity that are associated with volitional action and conscious experience, will undoubtedly shed light on the mechanistic differences among the highly heterogeneous, but functionally restricted, population of patients with disorders of consciousness."
Dr Steven Laureys, Coma Science Group, Cyclotron Research Center and Department of Neurology, University of Liege, Belgium T) +32 477972452 E) steven.laureys@ulg.ac.be
For Dr John Whyte, Moss Rehabilitation Research Institute, Elkins Park, PA, USA please contact communications director Alexis Moore +1 215-456-6734 JWHYTE@einstein.edu ; MooreAl@einstein.edu
full paper and comment: http://press.thelancet.com/TLNpainfinal.pdf
Journal
The Lancet Neurology