Calling patients in coma-like states by name is a simple and effective way of assessing what consciousness functions they still possess. Their own name triggers reactions in visible behaviour and in measurable brain activity not otherwise unleashed by less personal stimuli. These reactions provide crucial indications about rehabilitation potential, the prognosis and the optimum treatment. These insights were presented by Belgian and Chinese researchers at the 22nd Meeting of the European Neurological Society (Prague, Czech Republic, 9–12 June).
Gustave Moonen, Liège, Belgium, spoke on new coma research at the 22nd Meeting of the European Neurological Society (ENS): “Calling a person in a coma-like state by name is a simple tool that can lead to a much more accurate diagnosis. Any remnants of consciousness a person may have respond much more reliably to his/her own name than to non-personal stimuli. The differences manifest themselves in the patients’ visible behaviour and in the measurable activation of regions of their brain deemed responsible for self-perception according to our current knowledge. The more consciousness a patient possesses, the better the prognosis will be and the more intensive the rehabilitation efforts. We are therefore very happy to have found a tool that allows us to classify restricted states of consciousness much more reliably than before.”
Remaining consciousness potential can be activated only through intensive rehabilitation. If patients relying on a correct external assessment of their condition are categorised as being much less conscious than they actually are, the risk increases of suitable rehab efforts being applied with less intensity or omitted altogether. Moonen, secretary general of the ENS said: “The consequences of correctly decoding the state of consciousness range from appropriate care management and suitable therapies and rehabilitation measures to the difficult ethical questions that exist beyond the point where we set the end of human life and cease further measures to maintain the organism.”
Scientific use of the cocktail party effect
Moonen explained the neurological background of this diagnostic tool, namely people reacting to their own name, as follows: “This reaction appears to be the brain function equivalent of the well-known cocktail party effect. If our name is spoken in a babel of seemingly indistinguishable voices, we immediately perk up and pay attention but apparently only to the extent to which our self-consciousness is active. The measurement of activity in this brain region is therefore a way to draw conclusions about the degree of consciousness remaining in a person unable to communicate.”
Difficulty of assessing brain and consciousness functions in comatose states
The precise assessment of functions of the brain and consciousness in patients in different comatose states is a major challenge even for experienced specialists. After severe brain injuries resulting, say, from traumas or strokes, patients are often incapable of communicating.
In these cases, modern medicine describes several different stages. A coma is defined as a state of complete unconsciousness, a type of emergency shutdown of the brain for the purpose of regeneration and self-healing, from which it is not certain that the person will awake. When in a state of unresponsive wakefulness, formerly known as a vegetative state, affected patients open and close their eyes in accordance with the sleep-wake cycle, but they do not communicate. Patients in a minimally responsive state, formerly known as a minimally conscious state, respond to external stimuli.
It is often difficult to detect the differences, which is why there are no reliable figures on patients in states of limited consciousness. If American data is extrapolated, the European Union has about 33,000 to 72,000 patients in a state of unresponsive wakefulness.
Consciousness required to hear one’s own name
The researchers’ first step was to take functional MRIs of a healthy subject group in an alert state and in states of varying degrees of sedation. This examination showed that the naming of a person’s own name as opposed to other people’s names activated a substantial additional area (medial prefrontal brain region) but this effect declined with degree of consciousness.
Further studies by Steven Laureys (Coma Science Group, Liège, Belgium) and Hiebo Di (Hangzhou, China) and their teams were based on this finding. The studies showed that the extent to which the auditory cortex in the brain is activated in people in a vegetative state or minimally conscious state when they hear their own name is basically an indicator of their chances for rehabilitation. Laureys said, “However, we measured enormous deviations for stimulated regions of the brain at the individual points in time in which scans were made. Auditory consciousness can apparently drift off and then re-emerge again. More frequent examinations must be conducted so available potential is not overlooked.”
Calling patients by name also makes a big difference in simple clinical tests. The researchers stimulated 86 post-comatose patients in a state of unresponsive wakefulness or minimally conscious state by calling them by name and by ringing a bell for them; 37 of them responded with eye or head movements. Of this group, 34 responded to their name and only 20 to the bell – some to both. “The name is therefore much more suitable than a neutral sound for assessing the auditory function in people with a disturbed state of consciousness,” Laureys noted.
In a further test, the researchers addressed 30 patients diagnosed as minimally conscious, awakened from a minimally conscious state, or in a vegetative state (a state of unresponsive wakefulness) with their own name and asked them to raise their hand. The functional MRI scan showed an activation of the responsible motor cortex in five patients, two of whom had been diagnosed as being in vegetative state. “This is a definite sign of high-level cognitive functions that would have been impossible with the conventional assessment of external behaviour,” Laureys concluded. “These patients are obviously sufficiently conscious to understand the request otherwise the motor cortex would not have been able to be triggered. Owing to the type of brain damage involved, the pulse given there was unable to reach the muscles it wanted to move.”
Activation of the auditory cortex
The researchers from Liège also presented initial study findings at the ENS Meeting on the development of a further instrument for detecting remaining consciousness potential. The point of departure is the finding that spontaneous fluctuations in nerve activity occur in the auditory cortex both in an alert state and in an unconscious state. About every 20 seconds, the auditory cortex switches from concentrating on external stimuli to concentrating on internal processes and vice-versa. “Our studies on healthy subjects showed that the brain responded to acoustical stimuli much more intensively when switched to the external world than when switched to the internal world. However, this difference declined as sedation increased and consciousness dwindled. Thus, we were able to draw conclusions about the degree of consciousness still existent from the presence or absence of this difference in processing auditory impulses,” Moonen explained. “This finding must now be verified on an appropriately large number of patients with disrupted consciousness.”
