Initially, fMRI data were collected and analysed for 51 patients that made up the “Liege sample”. These individuals were selected based on their state of consciousness (VS/UWS or MCS) as repeatedly diagnosed with a high degree of certainty using the “Coma Recovery Scale-Revised”. In order to establish the validity of their classification method by means of fMRI in resting state, the researchers tested patients recruited in two other hospitals: Weill Cornell Medical College in New York, and Salzburg University Hospital. The results confirmed those that had initially been obtained in Liege: the automatic classification method worked in more than 90% of cases.

According to Dr Susan Whitfield-Gabrieli from the Massachusetts Institute of Technology, co-author of the article published in Brain, “we are faced with an important advance in the area of diagnosis by neuroimaging. The interest of progress in matters relating to fMRI technology applied to the resting state, is that we can gather the data in a systematic and highly reliable way in many centres around the world”. She adds: “In this way, the new paradigm goes beyond the imbroglios caused by behavioural performance in task-based activation studies”.

Test under anaesthetic?

The method does, however, have its limitations. On one hand, certain patients find themselves in an area very close to the boundary which statistical algorithms have established as the dividing line between the vegetative/non-responsive state and the minimally conscious state. The answer provided by the computer with regards to the binary “yes-no” method must be treated with caution. Also, it seems that the technique is only applicable, on average, in half of the scanned patients. Why is this so? Because the data collected from fMRI cannot be used when the patient has moved in the scanner, and this applies to 50% of cases. “We are studying the possibility of changing the paradigm for patients by conducting the test while the patients are under anaesthetic”, indicates Steven Laureys. “This approach has been the subject of much criticism because it is claimed that consciousness is absent when patients are in this state. Nonetheless, using fMRI technology, we have demonstrated that it is possible to demonstrate the wiring of the different networks. Lizette Heine, a research fellow at the FNRS, is currently studying the question in brain-damaged patients”.

Another question that begs for an answer is the predictive power of classifiers. Can they really make it possible to make a prediction with regards to the development of the state of consciousness of each patient? In other words, what can we expect for each patient when we base clinical outcome on the statistical values representing the distinction between the vegetative/non-responsive state and the minimally conscious state? According to Athena Demertzi, studies currently under way are not satisfactory when merely identifying signs of consciousness. It should also make it possible to predict the chances of a good recovery after a coma. However, this conclusion has yet to be confirmed for large groups which has not been the case up to the present.

FMRI during the resting state has become one of the tools for establishing possible signs of residual consciousness in patients suffering from severe brain-damage. It must be seen as a complementary tool for clinical examination, next to computer-brain interface and all the techniques relating to functional neuroimaging. One of the next challenges will be to combine this new approach with others in order to reduce the level of uncertainty with regards to the diagnosis and prognosis of these challenging patients.