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Krishna Chinthapalli: How to read the unconscious mind

20 Nov, 12 | by BMJ

Years ago, I stumbled across Roald Dahl’s macabre short stories whilst looking for tales of chocolate factories and witches’ conferences. In one of the most famous stories, William and Mary, a terminally ill husband, William, consents to a gruesome experiment upon his death. He lets a neurosurgeon keep his brain and an eye alive in a basin, using a machine to pump oxygenated blood to the organs. One of many interesting questions arising from the story was how communication is possible when the brain is unable to use any muscles for speech, the eyes, or movement.

In a BBC Panorama documentary last week, Fergus Walsh poignantly explored research into such communication in people with disorders of consciousness. In the first of five patient journeys—incidentally all were young men who had suffered brain injury in motor vehicle accidents—we see Alex have his 19th birthday party in the grounds of the Royal Hospital for Neurodisability in Putney, London. He was there for an assessment of his state of consciousness.

States of consciousness
A number of states of consciousness have been described in patients with brain injury. In the UK, brainstem death is equivalent to death of the person. It is diagnosed after testing multiple reflex pathways involving the brainstem, including testing for lack of spontaneous breathing. A coma is similar to brain stem death in that there is no wakefulness or awareness. However in a coma, there is often brain activity, movement to stimuli and spontaneous breathing. Coma usually progresses to brain stem death or to waking up.

A persistent vegetative state (PVS) is different from brainstem death and coma. A person in PVS is awake. We know that this is because their brainstem, particularly the reticular activating system, is working. These people show no awareness of the outside world though, although they have reflex responses and breathe normally. As with Alex in the programme, their eyes are open but they do not move to look towards anyone or anything.

The next step on the way to full consciousness is the minimally conscious state (MCS). This is when a person can make purposeful movements sometimes, but not always. In the programme, we meet Scott, a Canadian man in MCS after he was hit by a police car when crossing the road. He survived, but has not been able to speak or walk or even look around at the world for years. However, Scott sometimes lifts his thumb when his parents ask him a question.

Locked-in syndrome does not appear in the documentary, but often comes up in discussions of consciousness. People with this have full awareness, but are paralysed below their eyes because of a lesion in the pons, a part of the brainstem. This happened to Jean-Dominique Bauby, author of The Diving Bell and the Butterfly.

Of these, a major difficulty is differentiating people in PVS from those in MCS, and that is what the film focuses on.

Brain mapping and mind reading
Alex undergoes a thorough assessment with stimulation of all of his senses in the hospital, as well as preventive therapy, such as wrist splints to avoid contractures. Clinical assessment is the current mainstay for diagnosis of PVS and MCS. However, in the last decade, functional magnetic resonance imaging (fMRI) of the brain has been tried in these patients.

Alex and the other young men here are shown as they participate in fMRI studies led by Professor Adrian Owen, a British neuroscientist dubbed the “mind reader” by the narrator. Owen’s groundbreaking research has shown how fMRI can be useful to detect brain activity.

Alex is carefully placed in the MRI scanner for a series of tests. He is told to imagine playing a game of tennis and the researchers look for activation in the premotor cortex, the area of the brain responsible for planning movements. If there is activity, other questions can be asked. For example, in a memorable scene, Scott is asked to imagine playing tennis if he is not in any pain, but to imagine walking around his house if he is in pain. Much to his parents’ relief, the images suggest he is imagining the tennis courts.

The programme suggests that fMRI is a better way to distinguish between states of consciousness. Of course, the reality is not that simple. We are not told of the discrepancies in diagnosing vegetative states around the world or that 40% are misdiagnosed clinically. We are not told that the diagnosis may change because some people thankfully improve from PVS. We are also not told of the limitations of fMRI: in one of the largest studies to date by Owen’s team, only 5 out of 54 people in PVS and MCS showed definite cortical activation in response to commands.

On the whole though, it is fascinating to follow the patients in the research studies and highlights the work that still needs to be done in the diagnosis and management of these disorders of consciousness. Interestingly, BBC Panorama also spurred a national discussion on brainstem death criteria themselves back in 1980 when they provocatively asked “Transplants: are the donors really dead?”

Back in Roald Dahl’s story from 1960, the doctor is much more confident when asked by William if it is possible for his brain to communicate with others: “Well, Wertheimer has constructed an apparatus somewhat similar to the encephalograph, though far more sensitive, and he maintains that within certain narrow limits it can help him to interpret the actual things that a brain is thinking. It produces a kind of graph which is apparently decipherable into words or thoughts.” We do not have Wertheimer or such apparatus, but researchers like Adrian Owen and investigations like fMRI are helping to make a start in deciphering thoughts.

Krishna Chinthapalli is the BMJ clinical fellow.

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