Minimally Conscious Patients May Still Feel Pain

THURSDAY, Oct. 9 (HealthDay News) -- Unlike patients in a persistent vegetative state, patients in a minimally conscious state show pain processing brain activity similar to people who are conscious, implying that they need analgesic treatment, according to study findings published online Oct. 6 in The Lancet Neurology.

Mélanie Boly, M.D., of the University of Liège in Liège, Belgium, and colleagues conducted a study of five patients in a minimally conscious state, 15 patients in a persistent vegetative state and 15 controls who underwent bilateral electrical stimulation of the median nerve. The researchers studied brain activation with O-radiolabelled water positron emission tomography.

In the control patients and those in a minimally conscious state, cerebral correlates of pain processing were similar, and more widespread than in patients in a persistent vegetative state, the investigators found.

"The behavioral assessment of motor or autonomic signs (i.e., respiratory frequency, heart rate, blood pressure, pupillary diameter, and skin conductance) are not reliable markers of the conscious perception of pain, as shown in studies done in general anesthesia," the authors write. "The evaluation and treatment of pain is therefore an important clinical and ethical problem in patients in a minimally conscious state. In this context, functional neuroimaging can objectively measure changes in brain function during noxious stimulation in these patients."

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