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Functional MRI to Distinguish Between Vegetative and Minimally Conscious Patients

Brain activity was monitored as a close relative spoke the patient’s name.

Unlike patients in vegetative states, those in minimally conscious states (MCSs) retain some awareness. In this study of 11 patients — 7 thought to be in vegetative states and 4 thought to be in MCSs by clinical examination — Chinese researchers used functional MRI to evaluate brain activation while a close relative spoke the patient’s name.

The researchers assumed that activation limited to the auditory cortex (in response to the spoken name) implies no conscious awareness, whereas more widespread activation implies possible awareness. Functional MRI revealed activation in areas beyond the auditory cortex in all four MCS patients, but also in two of the seven patients thought to be in vegetative states. Three months later, the two vegetative patients with widespread activation had evolved clinically to MCS, while clinical examination of the other five patients (with activation limited to the auditory cortex) still suggested vegetative states.

Comment: In this study, researchers used functional MRI to distinguish between vegetative and minimally conscious states. The widespread activation noted in two clinically vegetative patients who later evolved to clinical MCS suggests that these patients might in fact have been incorrectly categorized as vegetative at the time of the MRI. Larger studies with longer follow-up are needed to determine whether this technique will provide clinically useful prognostic information.

— Allan S. Brett, MD

Published in Journal Watch General Medicine March 29, 2007

Citation(s):

Di HB et al. Cerebral response to patient's own name in the vegetative and minimally conscious states. Neurology 2007 Mar 20; 68:895-9.

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