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EEG scan helped contact patients in vegetative state

Electro-encephalography (EEG) helped doctors realize that several patients diagnosed as being in a permanently vegetative state were in fact aware, according to a study published on Thursday in The Lancet.

The technique could be developed as a portable, cheaper way of helping doctors make more accurate diagnoses and establish contact with patients who are immobile but aware, its authors say.

A persistent or permanent vegetative state is defined as "wakefulness without conscious awareness of self and environment." During a coma, by contrast, a patient lacks both awareness and wakefulness.

Researchers led by Adrian Owen and Damian Cruse at the Centre for Brain and Mind at the University of Western Ontario, Canada, carried out a test involving 16 brain-damaged patients in the vegetative state and 12 healthy controls.

EEG entails placing sensors on the scalp to record electrical signals that result from activity by brain cells.

Three of the 16 patients accurately and persistently showed a clear EEG response when they were asked to imagine movements of their right hand and toes, according to the paper.

Electrical signals on the top of their scalp matched those of the controls when the patients were asked to carry out this motor movement, even though their bodies did not make any motion.

The authors say they do not presume to draw conclusions about the "inner worlds" of the three patients on the basis of this experiment.

But they note that understanding the request and processing it in the brain was complex, requiring sustained attention, selecting the right response and understanding language.

"Despite rigorous clinical assessment, many patients in the vegetative state are misdiagnosed," the researchers say.

"The EEG method that we developed is cheap, portable, widely available and objective. It could reach all vegetative patients and fundamentally change their bedside assessment."

The technique is considered less sensitive than functional magnetic resonance imaging (fMRI), which monitors brain flow across the brain and has been used in several important experiments to determine awareness among vegetative patients.

But fMRI scanners are very expensive and cannot be used on patients with metal in their body, often the case with patients whose severe brain damage occurs in a car accident.

EEG diagnosis, if refined, could move beyond simple "yes/no" responses to include methods of communication that are more expressive, the authors say.

Development of techniques for real-time classification of different forms of mental imagery "will enable two-way communication with some of these patients, allowing them to share information about their inner worlds, experiences and needs," they conclude.

As opposed to brain death, persistent vegetative state is not recognised by legal systems as death.

"Lock-in" syndrome describes a condition in which mental functioning is normal, but the body inert and incapable of responding to commands.

 

<한글 기사>

식물인간과의 의사소통 더 쉬워진다

휴대용 뇌전도(EEG: 腦電圖)로 식물인간과 대화가 가능하다는 연구결과가 나왔다.

캐나다 웨스턴 온타리오 대학 뇌-정신센터(Center for Brain and Mind)의 애드리언 오언(Adrian Owen) 박사는 식물인간이 의식이 있으면 뇌전도에 반응하며, 따라서 식물인간이 의식이 있는지 없는지는 뇌전도로 알아낼 수 있다고 밝힌 것으로 AFP 통신과 영국의 일간 데일리 메일 인터넷판이 10일(현지시간) 보도했다.

오언 박사는 뇌 손상으로 식물인간 상태에 있는 16명과 건강한 사람 12명을 대상으로 오른손과 발가락을 움직이는 것을 상상하도록 주문하고 휴대용 뇌전도로 뇌파를 관찰한 결과 식물인간 중 3명이 정상인과 같은 뇌파를 나타냈다고 밝혔다.

이는 이 식물인간 3명이 주문을 인식하고 그에 반응할 수 있음을 보여준 것이라 고 오언 박사는 말했다.

이는 또 식물인간이 의식이 있다면 뇌전도를 통해 대화도 가능함을 시사하는 것 이라고 그는 덧붙였다.

식물인간의 의식 유무는 기능성 자기공명영상(fMRI)이라는 특수영상기술로 뇌의 활동을 관찰함으로써 알아낼 수 있다는 연구결과가 전에 발표된 일이 있다.

그러나 fMRI는 비용이 너무 고가이고 또 의료기관이 이 영상장치를 갖추지 못하고 있을 수도 있다. 또 뇌가 손상된 외상환자들은 사고 때 금속파편이 몸에 박혀 있을 수 있는데 이런 환자는 fMRI가 소용없다. 이에 비해 뇌전도는 비용이 별로 들지 않는다.

뇌손상 환자가 4주 이상 깨어나지 못하면 지속성 식물인간 상태로 간주된다.  이 는 "자기 자신과 주위환경에 대한 의식 없이 깨어 있는 상태"를 말한다. 이에 비해 혼수상태(coma)는 의식과 깨어 있음이 모두 없는 상태이다.

이 연구결과는 영국의 의학전문지 '랜싯(Lancet)' 최신호에 실렸다.

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