Detecting Awareness in Vegetative State

By: Adrian M. Owen, Martin R. Coleman, Melanie Boly, Matthew H. Davis, Steven Laureys, John D. Pickard

This is a fascinating report that may change the direction of research and the general perspectives on assessment and diagnosis of the vegetative state and the limits of clinical bedside assessment of consciousness. Dr. Owen, et al., present a case of a woman status post a traumatic brain injury 5 months earlier who clinically appeared to be in a vegetative state based on fulfilling "all the criteria for a diagnosis of vegetative state according to international guidelines" (Note: although based on the time frames could not be deemed permanently vegetative).

Functional Magnetic Resonance Imaging (fMRI) was used to measure her neural responses under several different conditions. The first examining patterns during presentation of spoken sentences which were compared with responses to acoustically matched noise sequences resulting in each specific activity being observed bilaterally in the middle and superior temporal gyri equivalent to that observed in healthy volunteers listing to the same stimuli.

The investigators then presented the patient with sentences that contained ambiguous words such as "creak/creek," which could mean either the noise or the small stream, and noted that this produced an additional significant response in the left inferior frontal region similar to that observed for normal volunteers. They hypothesized that this increased activity for ambiguous sentences reflected the operation of symantic processes critical to speech comprehension.

If this were not enough, they then tried to address the question of conscious awareness further by conducting a second MRI study during which the patient was given spoken instructions to perform two mental imagery tasks at specific points during the scanning procedure. One task involved imagining playing a game of tennis and the other involves one imaging visiting all the rooms in the patient's house, starting from the front door.

There were differential responses to each task. For the first task, fMRI demonstrated significant activity in the supplementary motor area whereas for the second task, significant activity was observed on fMRI in the parahippocampal gyrus, the posterior parietal cortex and the lateral premotor cortex.

Even more fascinating was the fact that the patient's neural responses per fMRI were indistinguishable from those observed in healthy volunteers performing the same imagery tasks under parallel scanning methodologies.

The authors concluded that their results confirmed the fact that the price of filling the clinical criteria for a diagnosis of vegetative state the patient in question retained the ability to understand spoken commands and to respond to them through her brain activity rather than through speech or movement.

They went on to note that her apparent cooperation in the imagery tasks further demonstrated a clear act of intention which confirmed "beyond any doubt," that she was consciously aware of not only herself but her surrounding.

The article, albeit brief, has rather profound clinical and research implications and should be read by all, as should the discussion by Dr. Lionel Naccache entitled "Is She Conscious?" in the same issue on page 1395-1396.

The authors of the paper should be commended for their novel approach to assessment of a patient in a disordered state of consciousness.

Hopefully, we will see further research on functional imaging as a window to assessing consciousness in persons with significant alterations in consciousness including coma, vegetative state, and minimally conscious state (MCS).

Science 
Volume 313, 9/8/06, Page 1402

Reveiw by:
Nathan D. Zasler, M.D., FAAPM&R, FAADEP, DAAPM 
CEO & Medical Director, Concussion Care Centre of Virginia, Ltd. and Tree of Life Services, Inc. 
Clinical Professor, Department of PM&R, Virginia Commonwealth University 
Chairperson, International Brain Injury Association