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Is fMRI a Useful Prognostic Tool in Early Vegetative State?
Eventually, it might be.
Investigators used functional MRI (fMRI) to study seven vegetative and four minimally conscious patients (age range, 21–61). Two patients (both vegetative) had experienced anoxia; the rest had traumatic brain injury (TBI). Investigations were conducted between 2 and 6 months post-injury for eight patients and 8 to 48 months post-injury for three patients. Cerebral activation was assessed by fMRI after presentation of the patient’s own name, spoken by a familiar voice.
The minimally conscious patients demonstrated activation of both primary and secondary auditory cortex. Two of the vegetative patients, ages 21 and 38, both assessed 4 months after TBI, showed similar activation of both primary and higher-order association cortex. These two patients emerged into the minimally conscious state by 3-month follow-up assessment. Three of the vegetative patients demonstrated activation of primary, but not secondary, auditory cortex, and the remaining two had no activation in either region; all five remained vegetative at 3-month follow-up.
Comment: This study adds to evidence that the brains of some vegetative patients support more cerebral processing of external stimuli than their behavioral state suggests and that such processing portends better short-term prognosis. Clinical status at 12 months was not described, so correlation with longer-term prognosis remains unknown. Thus far, the recovering patients have all been young, with recent (<6 months) TBI, consistent with already-known facts about prognosis in the vegetative state (N Engl J Med 1994; 330:1499). These results, thus, do not substantially alter the ethics of decision making for the cognitively devastated patient, although fMRI may eventually become a useful prognostic tool in the first few months of the post-traumatic vegetative state.
— Thomas I. Cochrane, MD, MBA
Dr. Cochrane is Instructor in Neurology, Harvard Medical School, and Brigham and Women’s Hospital, Boston.
Published in Journal Watch Neurology May 15, 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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