Functional MRI Detects Residual Awareness in Vegetative Patients

Activities

Copyright © 2007 AKSS, Inc. All rights reserved.

Susan Jeffrey

August 17, 2007 — In a follow-up to their earlier single case report, British and Belgian researchers have found several cases of patients in an apparently vegetative state who nevertheless show signs of brain activation on functional magnetic resonance imaging (fMRI), signaling cognitive function and conscious awareness.

With further research, the researchers are hopeful that detecting this type of covert awareness might make it possible to communicate with these patients or predict those who may recover from their vegetative state. However, the authors stress that they don't want to raise false hopes with this work.

"This is really at earliest days, and although we've shown that you can demonstrate conscious awareness in now several patients who are otherwise assumed to be vegetative, this is something that's extremely unlikely to apply to most cases of vegetative state, particularly those who have been in that situation for a long period of time," first author Adrian M. Owen, PhD, from the Medical Research Council Cognition and Brain Sciences Unit, in Cambridge, United Kingdom, told Medscape. "As we know, the chances of recovery from vegetative state decreases dramatically over time."

Their updated work is published in the August issue of the Archives of Neurology.

Covert Awareness

In 2006, Dr. Owen and colleagues reported a single case of a woman who was in a vegetative state following a car crash in 2005 (Owen AM et al. Science. 2006; 313:1402). Five months after her accident, the researchers scanned her brain using fMRI, asking her to imagine various scenarios such as imagining herself playing tennis or walking through her home, tasks they knew would produce activation in particular areas of the brain.

"When we did this, we saw that she would activate during several tasks in a way that was indistinguishable from a normal, healthy, awake individual," Dr. Owen said.

At the time, though, she was in a relatively acute stage of vegetative state; at 5 months, there remains a 20% chance of some recovery. And in fact, about 6 months after those initial scans in 2006, the patient did begin to show the earliest signs of recovery.

"She would fixate on an object placed in front of her face and her eyes would occasionally track something moving in front of her face," Dr. Owen said. The responses were intermittent, not consistent, but did signal that she was emerging to a minimally conscious state, he said.

"So one of the things we're quite excited about now is the possible prognostic value of techniques like fMRI for predicting which patients are most likely to show some signs of recovery vs those who remain in the vegetative state indefinitely," Dr. Owen said.

One in a Million?

Another question that arose with the original publication was whether this patient was the only one to exhibit such activation, he said. "We of course knew that that was very unlikely to be the case, but she was actually the very first patient we tried this in."

They have now scanned about 10 other patients and have again found a similar patient, a victim of traumatic brain injury, who responds in this way, exactly similar to healthy volunteers, he said. However, he said, "We also have many more patients who produce no activation at all.

"So the answer is that she's not the only patient, there are others out there like her, but she's also part of a minority, a small number of patients who we think have not only residual brain function but a level of residual brain function that will allow them to make responses with their brain to communicate with the outside world."

They are now working to see whether they can leverage the activation into a form of rudimentary communication. There are techniques using fMRI that allow people to use brain activation to spell words, he noted. "These things are working pretty well in healthy volunteers, and they've yet to be shown to be usable by any type of patient, but we are trying, because of course if one could open up an avenue of communication with these patients, that would certainly be 1 thing that could contribute to their general level of welfare, I think."

It is also possible that this residual activation may flag patients who will be more likely to recover to some degree from the vegetative state, and they are working now to follow up some of these patients. However, follow-up can be difficult, because, although they receive many referrals from "far and wide," he said, "it's actually quite difficult to follow people up, because they go back where they came from, and it's not straightforward." Funding is also a major problem at this point, since fMRI is quite expensive. "We urgently need more funding to investigate the efficacy of fMRI and similar approaches in answering these tricky diagnostic questions in acute brain injuries — it's an underfunded area at the moment, and we're working quite hard to remediate that problem."

The study was supported in part by a program grant from the Medical Research Council, the Smiths Charity, the Belgian Fonds National de la Recherche Scientifique, and the Mind Science Foundation. The researchers report no financial disclosures.

Arch Neurol. 2007;64:1098-1102.

Susan Jeffrey is news editor for Medscape Neurology and has been writing principally for physician audiences for 18 years. Most recently, she was news editor for thekidney.org and also wrote for theheart.org, both websites now acquired by WebMD. Prior to that, she covered neurology topics for 10 years at a Canadian newspaper for physicians.

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