Patients thought to be in a permanently "vegetative" state may still be able to think and communicate, a study has confirmed.
Scientists using a device to record brainwaves found "meaningful" responses from one in five patients who appeared unaware of the outside world.
Experts say it could change the way consciousness disorders are classified and may be a practical method for discovering the needs of patients, even whether they still want to live.
Researchers used a portable electroencephalography (EEG) device to record electrical signals from the brains of 16 patients diagnosed as being in a vegetative state.
They were told to imagine moving their right hand and toes although this was physically impossible.
Three produced repeated and appropriate brainwave patterns which showed they were aware of the commands and able to respond to them.
The study – which was published in an online edition of The Lancet medical journal – involved patients at Addenbrooke's Hospital in Cambridge and University Hospital of Liege, Belgium.
Previous studies have shown that functional magnetic resonance imaging scans can uncover awareness in apparently vegetative patients.
However, fMRI scans are expensive, are often unavailable and can produce confusing results.
Many brain-damaged patients also have metal implants due to traumatic injuries, which rule out MRI scans.
The EEG method is a "considerably cheaper and more portable bedside technique", said one of the researchers, Professor Adrian Owen, from the Medical Research Council's Cognition and Brain Sciences Unit, Cambridge.
"This method could reach all vegetative patients", he added.
Patients diagnosed as vegetative have periods of wakefulness but seem unaware of themselves or their surroundings.
The findings raise ethical issues. Previous research shows some patients with "locked-in syndrome" who cannot move or speak still find life worth living.
据英国《每日邮报》11月10日报道，一项研究证实，那些被认为处于永久植物人状态的患者可能仍然能够进行思考和沟通。
科学家用设备记录下了脑电波的活动，发现在那些看似对外部世界完全无意识的病患中，有五分之一的人做出了“有意义的”回应。
专家说这将改变意识障碍的分类方式，也是发现患者需求的一种实用方法，甚至能够用来观察患者是否还想继续活下去。
研究人员使用便携式脑电图仪记录了16名被诊断为处于植物人状态的患者大脑中传来的电子信号。
这些患者被告知想象一下移动自己的右手和脚趾，尽管他们的身体并不可能做到。
但重复三次出现的正确的脑电波模式显示出他们对于这些指令是有意识的，并且能够作出回应。
这一研究成果发表在《柳叶刀》医学杂志网络版上，其研究对象包括了剑桥大学阿登布鲁克医院和比利时列日大学校医院的病患。
以往的研究已经表明，功能磁共振成像扫描能够发现表面上是植物人的患者的意识。
可是，功能磁共振成像扫描非常昂贵，常常无法使用，而且会得出混乱的结果。
许多大脑受损的患者，由于外伤，脑中有金属植入物，这也排除了使用磁共振扫描的可能。
脑电图则是一种“相当便宜，更加轻便的床头科技”，研究成员之一，来自剑桥医学研究委员会认知和脑科学小组的阿德里安?欧文教授这样说道。
“这种方式适用于所有的植物人患者”，他补充道。
被诊断为植物人的患者是有清醒的时期的，但看起来似乎他们对自身和周围的环境都没有意识。
这一发现也提出了一个伦理学问题。以往的研究表明，一些患有“闭锁综合症”的患者虽然不能移动也不能说话，但仍认为生命是有价值的，想要继续活下去。
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