New Coma Scale Detects More Wakefulness in Some Patients

Emma Hitt, PhD

May 31, 2011

May 31, 2011 (Lisbon, Portugal) — A new scale used in the assessment of coma allows the detection of more consciousness in patients with severe brain damage, which may lead to more appropriate resuscitative care in these patients.

Prof. Steven Laureys, MD, PhD, head of the Coma Science Group in the Neurology Department at the University Hospital of Liège in Belgium, presented the report at the 21st Meeting of the European Neurological Society (ENS).

Prof. Steven Laureys

"Worldwide, physicians measure consciousness in severely brain damaged patients using a coma scale: the Glasgow Coma Scale (GCS), used since the 70s," Dr. Laureys told Medscape Medical News. "In our study, we used another more recent scale called the Full Outline of UnResponsiveness (FOUR) scale and showed it to be superior to find subtle signs of consciousness."

He added that the new scale offers the advantage of being able to be performed in intubated patients who are on a respirator, which currently includes most coma patients, and to identify nonverbal signs of consciousness by assessing visual pursuit (ie, eye tracking); hence, minimal signs of consciousness (about 10% in his study) are measured that are not assessed by the classic coma scales.

Also released here is proposed new terminology with respect to coma, developed by the European Task Force on Disorders of Consciousness, which it is hoped will infer less of a dismal prognosis and therefore may lead to less cessation of treatment in select patients.

New Terminology

Patients in a comatose state who are described as being in a "persistent vegetative state" often have a poor prognosis attributed to them, and this "has led to cessation of rehabilitation, neglect, and sometimes the ethically even more problematic decision to deny further feeding or other life-sustaining measures," Prof. Gustave Moonen, with the Department of Neurology at the University of Liege, stated in a statement from the ENS.

"We find it high time to propose a new, more neutral and descriptive term. By calling it 'unresponsive wakefulness syndrome' we describe what we clinically see but do not judge whether there is consciousness or not," said Dr. Moonen, a member of the European Task Force on Disorders of Consciousness.

New proposed terms for consciousness disorders include the following:

  • "Unresponsive wakeful" to replace "vegetative state" to indicate patients who have a functioning wake-sleep rhythm but show no response to commands and all their movements are reflexive.

  • The task force proposes substituting the common term "minimally conscious state" with "minimally responsive state (MRS)," a term that discerns 2 different stages. In "MRS-minus," patients show low-level behavioral responses, such as reacting to pain or following with the eyes. In "MRS-plus" they are additionally able to follow commands, to verbalize intelligibly, and/or to communicate nonfunctionally.

  • The term "functional locked-in syndrome" has been coined for patients showing no behavioral response but near-normal brain activity measurable by such technologies as functional magnetic resonance imaging, positron emission tomography, electroencephalography, or evoked potentials. These patients clearly seem to be conscious but not able to use their bodies to communicate.

"Overall, we hope that this new wording will help to herald a change in the ethical approach towards patients who need more, not less, attention by their environment, since they are not able to claim on their own their right to human contact," Dr. Laureys said.

FOUR Score

To assess the new scale, Dr. Laureys and colleagues compared the FOUR, GCS, and Glasgow Liege Scale (GLS) in 176 intensive care unit comatose patients who had had acute brain injury within the past month. Outcomes were evaluated 3 months after injury in 136 patients.

Although the FOUR, GCS, and GLS showed good reliability, 71 patients were considered in a vegetative/unresponsive state based on the GCS; however, the FOUR scale identified 8 of these 71 patients as being minimally conscious based on patients' visual pursuit.

According to the researchers, the FOUR score is a "valid tool with good interrater reliability that is comparable to the GCS and GLS in predicting outcome" and has the added advantage of including nonverbal signs of consciousness, such as visual pursuit.

"Recent studies have shown that patients with severe brain damage who show little outward signs of perception or understanding may have a certain degree of pain experience and awareness," Dr. Laureys said. "New methods of measuring awareness, such as this simple scale, could help doctors better treat these patients and give families an indication on whether their loved one is aware of their presence."

"I fully agree with the intention of Laurey's group to develop this scale," noted independent commentator Erich Schmutzhard, MD, professor of neurology and critical care medicine at the Department of Neurology, NICU Medical University Innsbruck, Austria. "Hopefully, with the new scale, the number of misdiagnoses will diminish," he told Medscape Medical News.

"At our institution, we use a very similar approach in our daily routine to assess the natural course of initially comatose patients developing into unresponsive wakefulness syndrome and then into a minimally conscious state or, better, a minimally responsive state." He added that clinically they treat patients, even those who are clearly profoundly comatose, "as though they can understand us."

This means that we're actually tracing down the elusive phenomenon called consciousness to very specific physiological parameters.

The FOUR score was also recently assessed in a report by Eelco F.M. Wijdicks, MD, from the Mayo Clinic in Rochester, Minnesota, and colleagues, published online May 11 in Neurology. In a pooled analysis of previous studies, they examined the specificity and sensitivity of the FOUR score vs the GCS in predicting outcome among 381 patients with neurologic injury.

Both scales performed equally well, but very low sum scores on the FOUR score provided good prediction of in-hospital and 3-month mortality. "A patient with a FOUR score of 1 or less has an 84% chance of mortality, while the mortality was only 44% in a FOUR score of 2 or greater," they write. The differences probably reflect a loss of brainstem reflexes, a prominent component of the FOUR score scale, they note.

"The robust predictive value of the FOUR score and low sum scores provides us with the opportunity to investigate this in a prospective manner in patients with a catastrophic neurologic injury who are deteriorating," Dr. Wijdicks and colleagues conclude. "It also provides the opportunity to better assess comatose patients in clinical trials."

Clues From Sleep and Connectivity

More than 250 sensors measure the electrical response of the brain to auditory stimuli in coma patients and allow physicians to detect signs of consciousness. Copyright: comascience.org

Finally, several other interesting observations by the group from University Hospital of Liège, Belgium, in collaboration with researchers from Italy and the United States were also presented here:

  • Using high-density EEG, the researchers examined brain activity during sleep among those in a minimally conscious and vegetative (now wakeful unresponsive by the new terminology) states. They found behavioral but no electrophysiologic sleep-wake patterns among patients in a wakeful unresponsive state but "near to normal" patterns in patients in a minimally conscious state. "We suggest that the study of sleep and homeostatic regulation of SWA [slow wave activity] may provide a complementary tool for the assessment of brain integrity," in these patients, the researchers, with lead author M. A. Bruno, conclude.

  • The same group also used a combination of EEG and transcranial magnetic stimulation to assess cortical effective connectivity in vegetative (wakeful unresponsive) or minimally conscious states, as well as 2 patients with locked-in syndrome after brain injury. A key requirement for consciousness is connectivity, that is, that multiple specialized cortical areas can interact rapidly and effectively, the study authors note.

"Using high-density EEG measurements we discovered that in a wakeful unresponsive state, only bottom-up connectivity but never top-down feedback could be recorded, indicating a breakdown of effective connectivity," Dr. Laureys said in a statement from ENS. "On the other hand, patients in a minimal conscious state or recovering from wakeful unresponsiveness to MCS or higher states of consciousness showed near-normal cortico-cortical feedback loops. This means that we’re actually tracing down the elusive phenomenon called consciousness to very specific physiological parameters.

"Just as the second half of the 20th century is rightfully called the era of uncovering the genetic code, the first half of the 21st century might one day be called the age of cracking the code of consciousness," Dr. Laureys concluded. "Being able to correlate consciousness to specific brain activities, we may expect essential insights into the criteria for being an individual human being, as well as into the border areas between life and death."

21st Meeting of the European Neurological Society (ENS): Oral abstracts 238, 242, and 267. Presented May 30, 2011.

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