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Experts Call for More Research on Minimally Conscious State

Sporadic reports of brain injured patients “awakening” after a period of minimal responsiveness, together with new research suggesting that the brain can have some ability to heal, underscore the need for a major research effort to understand the condition and identify patients who might recover, according to an article in the Jan. 23 issue of Neurology.

“If America was confused by the Terri Schiavo case, how will it respond to new knowledge about disorders of consciousness and the capability of the brain to recover in the face of overwhelming injury?” the authors ask in summarizing an Institute of Medicine (IOM) exploratory meeting in which a panel of experts recently discussed what little is known about the minimally conscious state (MCS).

The term MCS was coined in 2002 to describe a condition of brain-injured patients who have transient episodes of awareness (Neurology 2002; 58:349–353). Formally stated, MCS is “a condition of severely altered unconsciousness in which minimal but definite behavioral evidence or environmental awareness is demonstrated.” In contrast, patients in a persistent vegetative state (PVS), like Terri Schiavo, have no awareness of self, others, or the environment, and no chance of recovery.

Although episodic, MCS patients demonstrate “unequivocal evidence of consciousness” including attention, intention, and memory; they can follow objects with their eyes and even communicate on a rudimentary level.

Some MCS patients may show major additional recovery within the first year, but this potential is generally unrecognized under the existing system of care, according to lead author Joseph J. Fins, MD, chief of medical ethics at New York Presbyterian Hospital-Weill Cornell Center in New York City.

“Most MCS patients are currently released from acute care centers after several weeks and warehoused in what are euphemistically called custodial care facilities, without access to subsequent evaluation by neurologists experienced in recovery during the critical one-year following injury when some degree of improvement might be possible,” Dr. Fins told Neurology Today in a telephone interview.

IOM REPORT

The exploratory panel recommended that the IOM prepare a report elucidating the need for targeted research in this area and the “unique opportunities” available for studying consciousness disorders using emerging neuroimaging and related technologies. The report should include strategies for identifying patients with MCS, including potential diagnostic and prognostic markers, and epidemiological surveys to better differentiate MCS patients from those in PVS.

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Dr. James L. Bernat: “The AAN is responding to our growing awareness of differences between the vegetative and minimally conscious states, and putting together a panel of experts to inform a definitive review, but this will take at least one-and-a-half to two years.”

The case of Terry Wallace illustrates why making this distinction is important, said Dr. Fins. In June 2003, Wallis emerged from 19 years in what was thought to have been a vegetative state, but was in fact MCS, and he has since sustained progressive recovery, including fluent speech. Yet throughout the long ordeal, requests by his parents for neurological re-evaluation and neuroimaging tests were denied.

“Patients leave academic neurology centers at some point early in the first year, but many can change within that year,” he said. “Signs of consciousness reported by family members and caregivers are too often dismissed as wishful thinking or hopefulness. What we need are comprehensive longitudinal studies. This is a scientific question, not an ideological one. This is about making an accurate diagnosis. Signs of attention in these patients are episodic and easily missed, and the diagnostic error rate today is unacceptably high.”

Some estimates place the error rate — MCS patients mistakenly classified as PVS — as high as 40 percent. Between 112,000 and 280,000 patients may fall into this category, said Dr. Fins, but this estimate is based on a single study extrapolated from a heterogeneous group of pediatric patients.

There is no way of knowing how many patients recover after a period of vegetative or minimal consciousness – one of the reasons why epidemiological studies are needed, he said.

“Another important point is that traumatic brain injury has been described as the signature injury of the Iraq war,” Dr. Fins noted. “This should give additional impetus to characterize the full continuum of consciousness that can exist following brain injuries. The time is ripe to engage this fully.”

The authors are also preparing a report for the U.S. Congressional Brain Injury Task Force, which will include a research and policy agenda, he noted.

AXONAL POTENTIAL?

Nicholas D. Schiff, MD, associate professor of neurology and neuroscience at Weill Medical College of Cornell, and colleagues at the JFK Johnson Center for Rehabilitation in Edison, NJ, had used diffusor tensor imaging (DTI) to produce an image of the white matter in the brain of Terry Wallis. In a 2006 study in the Journal of Clinical Investigation, they presented quantitative structural and functional neuroimaging data, suggesting growth of new axonal connections in damaged brain areas that corresponded with motor recovery (116: 2005–2011).

“The findings suggest a potential biologic mechanism for late recovery in patients … but may not play a role in other patients with different underlying etiologies of brain damage, a hypothesis that requires further testing in many patients,” according to the Neurology article. “It is, however, unlikely that slow axonal regrowth is the sole explanation for the changes observed in the subject. Additional factors that influenced the patient's recovery remain unknown,” the authors wrote.

“There appears to be some potential for additional recovery in these patients, although who will emerge from this state and what mechanisms are involved remains to be seen,” Dr. Fins told Neurology Today. “It's a cultural problem in some respects. The right to die is critically important and is historically associated with patients in the vegetative state. Now we're asking society to think differently about MCS patients with whom vegetative patients are erroneously conflated. It's bound to create some cognitive dissonance,” he said.

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Dr. Timothy E. Quill: “Clinical assessment must take place over a period of time, not just after the injury, and the degree of recovery that might be possible is different for each patient.”

“In many ways, as a declarative statement, ‘there is no hope for meaningful recovery,’ has always had an authoritative finality, but now we may need to be more cautious in our diagnostics and prognostications. We have to accept that there's going to be some ambiguity,” he said.

James L. Bernat, MD, professor of neurology at Dartmouth Medical School in Lebanon, NH, agreed with the need for comprehensive research on the condition in light of the recent neuriomaging studies and the extent of this previously unrecognized group of traumatic brain injury patients.

“Prior to 2002 MCS wasn't even considered a category, even though it's much more common than PVS, perhaps ten times more common,” he told Neurology Today in a telephone interview. Dr. Bernat is a member and former chair of the AAN Ethics, Law and Humanities Committee. He said the committee is currently preparing a report on the issue.

“The AAN is responding to our growing awareness of differences between the vegetative and minimally conscious states, and putting together a panel of experts to inform a definitive review, but this will take at least one-and-a-half to two years,” he noted.

ONGOING ASSESSMENT

Timothy E. Quill, MD, professor of medicine and director of the Center for Ethics, Humanities and Palliative Care at the University of Rochester School of Medicine in Rochester, NY, said the task ahead is likely to be difficult.

“I think this is a good time for this discussion to begin, and a good call on the part of the authors,” he told Neurology Today in a telephone interview. “If you look at injured patients early on, it's difficult to tell the difference between PVS and MCS — it depends to a large degree on the skill of the neurologist. But MCS is much more common than PVS, and in many ways much more troubling. These patients are conscious at some level, and that makes everything more frightening. With PVS the patient isn't capable of suffering, but that cannot be said of those in a minimally conscious state.”

Not much is known about the condition other than patients need to be evaluated with expertise, he said. “Clinical assessment must take place over a period of time, not just after the injury, and the degree of recovery that might be possible is different for each patient.”

Regardless, patients and their families will be the ultimate decision makers when it comes to life support, he noted.

“Many people want to be kept going in either condition, no matter what, even if their chances of any recovery are only 1 in 1,000. Others say the odds aren't good enough. This isn't an exact science, and knowing that a loved one might be conscious, no matter how minimally, causes a lot of angst. The issue has become a lot more complex.”

He said he believes there should be repeated visits for evaluation by experienced neurologists for the first three to six months.

“If you don't see anything suggesting consciousness after that time, it's extremely unlikely that there will be any later on.”

ARTICLE IN BRIEF

Experts says more research must be done to elucidate strategies for identifying potential diagnostic and prognostic markers, as well as epidemiological surveys to better differentiate patients in a minimally conscious state from those in the persistent vegetative state.

REFERENCES

Fins JJ, Schiff ND, Foley KM. Late recovery from the minimally conscious state: Ethical and policy implications. Neurology 2007;68;304–307.
    Voss HU, Ulug AM, Dyke J, et al. Possible axonal regrowth in late recovery from the minimally conscious state. J Clin Invest 2006;116:2005–2011.
    Giacino JT, Ashwal S, Childs N, et al. The minimally conscious state: definition and diagnostic criteria. Neurology 2002;58:349–353.
    Lammi MH, Smith VH, Tate RL, et al. The minimally conscious state and recovery potential: a follow-up study 2 to 5 years after traumatic brain injury. Arch Phys Med Rehabil 2005;86:746–754.