Under the Microscope/Prof William Reville:Most people have heard of cases where patients spontaneously "woke up" from a comatose or vegetative state to report that they had been conscious all along but couldn't make their bodies communicate this fact to observers in the room.
What a comfort it would have been to people who loved the patient, and to the patient, if everyone had known that they were mentally aware and responsive all along.
A breakthrough in this field was made recently. In 2006 a team of British researchers announced (Science, September 8th, 2006) that they had imaged the brain of a vegetative patient to discover she was conscious and aware. The team has now developed a method to ask yes-or-no questions of such patients. Up until now such people were thought to be beyond treatment, but these developments may make it possible to reach and to help them. The story is summarised by Karen Schrock in Scientific American Mind April/May 2007.
Medically, consciousness is divided into two components - wakefulness and awareness. Disorders of consciousness are defined as follows: coma (neither awake nor aware); vegetative state (awake but not aware); minimally conscious state (awake but severely limited responsiveness).
Prior to the 1970s, comatose and vegetative state patients received only palliative care. Neurorehabilitation began in the 1970s when each individual's brain injury was examined to see if treatment would be possible. Magnetic resonance imaging (MRI) was a great advance in the 1980s and allows radiologists to map the structure of the brain. The cylindrical tube of the MRI scanner houses an electromagnet that can produce a magnetic field 50,000 times greater than the earth's field.
This field coaxes the magnetic nuclei of atoms to line up in the direction of the field - normally they are randomly orientated. When the magnetic signals line up they can be induced, using radiowaves, to produce a coherent signal that can be measured. In MRI, it is the magnetic signal from hydrogen atoms in water that is measured. The strength of the signal depends on the surroundings allowing the MRI technique to discriminate between grey matter, white matter and cerebrospinal fluid in structural images of the brain.
In the 1990s a brilliant refinement of MRI called functional MRI (fMRI) began, which makes it possible to see and map activity in the brain. Areas that are active increase their metabolism, which calls for more oxygen and enhanced blood flow to the region. fMRI scans detect a magnetic signal associated with increased use of oxygen.
Adrian Owen of Cambridge University led the team that detected consciousness in the brain of a woman in the vegetative state. Using fMRI they imaged the woman's brain as she was asked to respond to various requests. The researchers asked the woman to visualise carrying out activities such as walking through various rooms in her house, while they imaged her brain using fMRI. They carried out the same procedure on healthy test subjects. The same areas of the brain lit up in both the patient and the healthy volunteers, showing that the woman had understood the requests and had intentionally decided to comply.
When Owen and his team did the research, it took several days to interpret the fMRI scans. However, the technique has now been improved to such an extent that the scans can be interpreted in 30 to 40 seconds. This opens the possibility of reading the patient's mind live as he/she thinks. Owen's team is now developing a procedure for having two-way communication with a person in the vegetative state who is mentally aware. They ask for yes-or-no answers to questions and instruct the patient to visualise playing tennis, for example, if the answer is yes, and to visualise walking through rooms if the answer is no.
Not all comatose or vegetative state patients are mentally aware. This breakthrough offers the hope of detecting those who are conscious, and these patients can then be targeted with intensive therapies in the hope of bringing them back to full normal consciousness. Unfortunately, some or many comatose/vegetative state patients will have suffered brain damage that is irreversible. Incidentally, the female subject of the research carried out by Owen's group subsequently improved from her seemingly vegetative state.
For the moment, the technique of using fMRI to diagnose or communicate with brain-damaged patients is confined to a small number of research laboratories. It will take several years to understand how to use this technique to best advantage in clinical settings. Nor can researchers entertain requests from distraught relatives of patients to carry out brain scans. More research is needed before the researchers can be confident that their interpretations of the scans are correct. Also, funding for this research is scarce and the equipment necessary is very expensive. A fully equipped fMRI scanner costs several million euro.
I will finish with the story of Colorado woman Christa Lilly (49), who fell into a minimally conscious state after a heart attack and stroke in 2000. Her eyes are open but she doesn't appear to be conscious of her surroundings. She recently woke up for three days, talked to her family and met her grandchildren for the first time. She even gave an interview on TV before slipping back into the minimally conscious state again. She said waking up was "wonderful" and "makes me so happy".
Her medical carers cannot explain why she woke up.