Imagine you have a brain injury that leaves you able to see and hear what is happening around you, but unable to communicate with the outside world. How can your carers know whether or not you are conscious? More and more people now survive brain injury due to improved trauma care, but end up in vegetative or minimally conscious states. Research, described by Adrian Owen in Scientific American (May 2014), is making great strides both in determining which patients retain awareness and in communicating with them.
Owen categorises classes of compromised consciousness as follows – brain-death: all brain functions permanently lost; coma: complete loss of consciousness, no cycles of sleeping/waking, eyes closed; vegetative state: sleep/wake cycles occur, eyes may open spontaneously but behaviours are reflexive; minimally conscious state: patients seem vegetative but sometimes show signs of awareness; locked-in syndrome: patients are conscious but cannot move and seem to be in vegetative or minimally conscious state. Many can still blink and move their eyes.
Owen's interest in this area began in 1997 when he came across a female patient (Kate) who had lapsed into a vegetative state after an illness. Her eyes would open and close fleetingly. She appeared to look around, but showed no signs of inner life. Owen examined Kate's brain responses in a Pet scanner to seeing photographs of friends and family. To his surprise not only did her brain respond to the faces, but its activity patterns were similar to the brain responses of healthy aware individuals when shown pictures of loved ones. Was Kate conscious or was this a reflexive response? Owen began more in-depth research.
He started by playing speech and also speech-like noises devoid of actual speech to patients in diagnosed vegetative-state conditions. Brain activity was recorded in speech perception regions of their brains in response to speech but not to the noise. However, the same result was recorded with subjects rendered unconscious by an anaesthetic. The brain processes speech automatically. A different type of brain activity must be recorded to determine if the patient is conscious.
Owen next discovered that when normal subjects are asked to visualise performing certain tasks, for example playing a game of tennis or walking through the rooms in your house, regions light up in the brain, seen through fMRI imaging, that are characteristic of the particular activity. Owen's team then tested a woman in a vegetative state and got the same result. She was asked to visualise two tasks sequentially – playing tennis followed by walking through the rooms in her house. She did this repeatedly and the characteristic brain activities were recorded each time. The vegetative state patient was conscious. A survey (New England Journal of Medicine, 2010) showed 17 per cent of vegetative-state patients are conscious.
‘Squeeze my hand’
To establish
two-way communication
with such patients, Owen followed the “squeeze my hand if you hear me” approach. While monitoring the brain in an fMRI machine he asked a vegetative-state but conscious patient questions with a Yes or No answer and instructed him to visualise a certain activity (playing tennis, for example) when the answer is yes, and another activity (such as walking through the rooms in his house) when the answer is no. This technique worked and is now used to communicate with such patients. But communicating through fMRI machines is awkward and expensive and cannot be done at all if the patient has metal implants, so Owen’s group is now developing techniques using simple portable ECG equipment.
The ability to detect and communicate with the covert consciousness of patients in vegetative states has obvious implications for patient care. For example, medical staff can ascertain whether the patient is in pain or discomfort and alleviate this. And obviously, the discovery of consciousness when the decision had already been made to withdraw nutrition and hydration could be used to legally overturn that decision. In that regard, Owen reminds us that people have an amazing capacity to adapt to extreme disability – in a 2011 survey of 65 patients with locked-in syndrome, most expressed satisfaction with the quality of their lives.
One can imagine the anguish one would feel to be conscious but unable to communicate with the outside world. The results achieved by Owen’s group are thus truly heartwarming.
William Reville is an emeritus professor of biochemistry at UCC. understandingscience.ucc.ie