Patient in intensive care (artist's view) -
© Mohamed Hassan / Pixabay
The comatose state is clinically characterized by four stages and three evolutions, according to a study published by our partner The Conversation.
The famous tool known as the “Glasgow scale” is gradually replaced by the one known as the “Glasgow-Liège scale”, which allows a more detailed assessment of the severity of a deep coma.
The analysis of this phenomenon was carried out by Philippe Menei, professor of neurosurgery, head of the Angers CHU department and research professor of the Inserm U1232-CRCINA unit at the University of Angers.
Coma is generally considered to be the most severe form of impaired consciousness.
But what is consciousness?
Philosophers, psychologists, physiologists, neurobiologists… everyone has their definition.
We will adopt that of the clinician.
For him, it is a state of physiological cerebral activation (awakening), which allows him to perceive the outside world, and to adapt his responses (elementary or complex) to the requests.
Specifically, a comatose patient does not react or react inappropriately to stimuli from the outside world.
In practice, the coma occurs suddenly following a head trauma, a cerebrovascular accident, a sudden drop in oxygen supply, or even meningoencephalitis.
From the outset, two questions arise for neurosurgeons and resuscitators, raw and direct: what is the severity of the coma, in other words its depth?
And what is the probability for the patient to regain normal consciousness?
These are essential questions when it comes to providing the best possible care for the some 1,500 patients who are currently in a state of non-responding awakening or of altered consciousness in our country.
Four stages, three evolutions
For a long time, the classification of coma was based on four stages:
stage 1, when communication is reduced but possible;
stage 2, when there is no communication but reactions to painful stimuli;
stage 3, when the patient no longer reacts at all to painful stimuli;
stage 4, when life is only maintained by artificial means: this is called a coma passed.
In addition, three changes were envisaged: improvement with better perceptivity and reactivity, brain death quickly followed by the death of the patient, or a vegetative coma.
This vegetative state was defined in 1994 as a "clinical condition devoid of any (manifestation of) awareness of self and of the environment, associated with the presence of the wake / sleep cycle with full or partial maintenance of the automatic functions of the hypothalamus. and brainstem ”.
A state in which the eyes are open, reflex movements present, but where there is no reaction to verbal commands or other stimulation - which has led some to see it as a functional awakening without conscious mental life and without awareness of the world around.
A doctor and a patient in intensive care © Shutterstock (via The Conversation)
Advances in resuscitation in recent decades, however, have helped keep patients with major brain damage alive.
At the same time, new physiological exploration methods, such as positron emission tomography (PET) and especially functional magnetic resonance imaging (fMRI) have upset the notions of perception and reactivity in the comatose patient, as well as the limits assessment of disturbances of consciousness.
Glasgow scale
To estimate the depth of a coma, the four stages used since World War II have come to show their limits.
It was necessary to have a tool which remains easy to use, giving identical results from one examiner to another, but whose evaluation was finer.
This is why the use of the Glasgow scale (or Glasgow score - GCS) has developed, initially designed to assess the severity of comas in adults following a head trauma.
Very quickly, the use of this scale was extended to other groups of patients, sometimes with variations (for example in pediatrics, or for deep comas).
The GCS has thus become the most widely used score in the world.
Three criteria are evaluated: the opening of the eyes, noted on 4, the verbal response, noted on 5, and the motor response, noted on 6. The sum of the scores ranges from 3 (deep coma) to 15 (consciousness. normal).
And we talk about coma or unconsciousness when the patient has a score below 8.
The Glascow Scale
Despite its simplicity, the Glasgow Scale does not always give the same results depending on who uses it.
In addition, it suffers from several limitations of use.
For example, for verbal scoring in patients with speech impairments or intubates.
Or, for the visual assessment in the event of orbital edema.
But also, when it comes to choosing the side to retain in case of asymmetry in the motor response.
Finally, it does not make it possible to differentiate between coma and Locked-in syndrome, where the subject is completely paralyzed, but conscious.
Evaluate reflexes to improve the Glasgow scale
To remedy these problems, in 1982, Jacques Born's Belgian team added to the Glasgow scale the assessment of several brainstem reflexes, rated from 5 to 0: the fronto-orbicular, vertical oculocephalic, photomotor reflexes. , horizontal oculocephalic and oculocardiac.
Henceforth called Glasgow-Liège (GLS), and with a score ranging from 3 to 20, this scale allows a more detailed assessment of the severity of a deep coma, in the lowest scores (3 or 4).
Glasgow-Liège scale
However, there remained a problem: the GLS score was not shown to be more sensitive than the GCS score in the evaluation of residual consciousness during the vegetative state.
In fact, patients in whom such a diagnosis had been made presented temporary signs of consciousness, with the continuation of the gaze, tears or smiles, even gestures, in response to a strong emotional stimulus (their reflection in a mirror, the presence of loved ones, music linked to a vivid memory…).
It is to take into account these fleeting, but above all extremely fluctuating signs of consciousness that the notion of minimal or altered consciousness was forged in 2002, to which the name pauci-relational state is also given.
However, four years later, in Cambridge, the neuroscientist Adrian Owen and his team published a work as innovative as it is disturbing.
Based on functional magnetic resonance imaging (fMRI), this study showed the existence of a preserved consciousness in a young patient for whom the diagnosis of vegetative state had been made: when he was asked to 'imagine playing tennis or moving around your house, the same cortical areas were activated as in healthy volunteers!
The use of different strategies for exploring the metabolic (positron emission tomography and functional MRI) or electrical (electroencephalogram) activity of the brain has therefore developed.
Our “Brain” file
Reveal consciousness in pictures?
These imaging-based examinations consist in measuring the patient's brain activity either at rest, or when asked to perform cognitive tasks, or when subjected to external stimulation.
Under these conditions, more than one in ten, it is observed that despite his "vegetative state", the patient is able to follow instructions.
These functional imaging methods have therefore revealed that said “vegetative state” is far from corresponding to what this expression implies - not to mention its pejorative connotation.
For this reason, in 2010 the Belgian team led by Steven Laureys proposed replacing the name “vegetative state” with another name: “non-responding arousal syndrome”.
Ultimately, today, the level of alteration in patients' consciousness is no longer defined solely by their ocular, verbal, motor or reflex reactions to stimuli, but also by more detailed measurements of the metabolic activity of the patient. brain.
New investigative methods such as electrical stimulation and virtual reality could lead us tomorrow to define it differently (our team will soon launch a clinical trial based on virtual reality to wake up from coma).
We can also hope that in the future, brain-machine interfaces will offer all these patients the possibility of reacting to stimuli from the outside world, or even of communicating.
There is no doubt that such a development will not fail to open up a complex ethical debate.
Health
Alzheimer's: Ten factors that increase the risk of developing the disease
High Tech
Why artificial intelligence still (temporarily) struggles to match the human brain
This analysis was written by Philippe Menei, professor of neurosurgery, head of the Angers CHU department and research professor at Inserm Unit U1232-CRCINA at the University of Angers.
The original article was published on The Conversation website.
Video
Health
Medicine
Coma
Brain
MRI