On a behavioural level, the difference between the two types of patient is clear. But what about brain activity? To find out, we used positron emission tomography (PET scan) to scan patients in a “minimally conscious state +” and others in a “minimally conscious state –“. The first group showed a higher level of metabolic activity than in the second group within the areas of language and motor activity. We know that patients who respond to the instruction have access to language and, on the basis of the brain's metabolism and behavioural tests, we believe that patients who don't respond to it, don't have access.son that patients dients dnde havas of patient is clear.g s the w.ales and electrophysiology, should be sufficient  The next question would be: is the level of consciousness between the two groups different and, more broadly, can consciousness as such be graduated? Some researchers have suggested the existence of two types of consciousness: primary or sensorial consciousness and more extensive or higher level consciousness. Does this reflect reality? We are therefore in a phase of fine-tuning the concepts and, consequently, fine-tuning the diagnosis among severely brain-damaged patients.



Your book also reveals that the treatment of people with disorders of consciousness is entering a new era?

Up until recently, we didn’t know which treatment to use to try to increase the level of consciousness in these patients. Pharmacological options that are in the process of being validated now seem to be a possible way forward. Furthermore, a lot of hope is placed on Deep Brain Stimulation. With this technique, an intracranial electrode is placed at the level of the thalamus with the aim of stimulating the thalamocortical connection; in 2007, Professor Nicholas Schiff from Cornell University New York, with whom we collaborate for many years, already demonstrated the importance of it in regaining consciousness.

On a neuroanatomical level, consciousness involves the activation of several nuclei spread between different areas of the associative cortex, as well as thalamocortical loops, i.e. circuits that connect the thalamus with regions of the cortex. We have shown that consciousness seems to be indissociable from these retroactive loops.

Is the issue of prognosis relating to patients recovering from a coma also a key stake?

A good diagnosis isn’t everything. It is indeed vital to be able to determine the patients’ chances of recovery. All the more so since knowledge of this parameter is of key importance in access to care and end-of-life decisions. A federal project coordinated by Marie-Aurélie Bruno was set up in order to follow the evolution of seriously brain-damaged patients who had recovered from a coma. More than 500 people were assessed after one, three, six and twelve months. Some were in a vegetative state while the others were in a minimally conscious state. The study also made a distinction within these two categories, depending on whether the origin of the damage was traumatic or not (cerebrovascular stroke, cardiac arrest, etc.).

In this multicentric study, all the centres used the same assessment tool: the Échelle de récupération du coma (Coma recovery scale), validated in French by the Coma Science Group in 2008. It appeared that the earlier the signs of consciousness, the better the recovery of functional communication, defined as the ability to respond positively or negatively to a question. In other words, the prognosis is all the more favourable if the subject rapidly reaches a minimally conscious state. Furthermore, patients with damage resulting from a trauma fare better. Why? Because the damage they are suffering from is often relatively focal, while in patients who have suffered anoxia (lack of oxygen to the brain), for instance, a more extensive part of the brain is affected in general.

What do the statistics tell us in concrete terms? That about 25% of patients in a vegetative state recover functional communication after a year if the origin of the damage is traumatic, compared with only 2% if it results from another etiology.  The figures are about 50 and 25% respectively with regard to a minimally conscious state.