Coma is a prolonged state of unconsciousness, caused by an injury (for example, a head injury), an accident or an underlying illness (although there are also induced comas).
The comatose state rarely lasts more than 2 to 4 weeks, although some can last for many years (even decades). In this sense, the duration and sequelae depend on factors such as: the cause, severity and site of the injury.
People who come out of a coma may present various problems or consequences: physical, intellectual and psychological. For people who have been in a coma for many years, the most common cause of death is an infection, such as pneumonia.
A confusing experience
People who have gone through a coma often describe this experience as diffuse, strange and very confusing.
However, not all people experience the same thing when in a coma, although there is always an inability to make voluntary movements, as well as to feel or respond to environmental stimuli.
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But what else do we know about this peculiar state of consciousness that generates so much fear and uncertainty?
What is coma and what are its causes?
Coma consists of “a prolonged state of unconsciousness”; During this state, the person cannot wake up or respond to environmental stimuli (for example: a sound, a light, a painful stimulus…). In addition, he cannot carry out actions voluntarily and does not have a normal sleep-wake cycle.
The onset of coma can occur due to a failure in the central nervous system (CNS), although in other cases, coma is induced.
When it is due to a failure in the CNS, dysfunction occurs at the neuronal level, whether due to a structural or non-structural process. Infectious or metabolic processes that affect the brain are also involved in the origin of coma. Among these processes we find: massive alcohol intake, hypoglycemia and hyperglycemia, excessive drug consumption or the use (or abuse) of illegal drugs.
During a coma, the brain receives a limited supply of glucose and/or oxygen. If the loss of nutrients is notable, neuronal damage occurs in the person’s brain. This neuronal damage can also occur due to a direct injury to the brain tissue, as a result of hemorrhage or an internal contusion that damages the cellular structure of the brain.
What does the person who is in a coma feel?
Davinia Fernández-Espejo, psychologist and speech therapist at the University of Oviedo, currently a researcher on consciousness and its disorders at the University of Birmingham, assures that “some patients who appear to be in a vegetative state are actually aware of themselves and their environment. and they are able to create memories and imagine things like anyone else.”
However, they cannot respond to the environment because an important communication pathway in the brain is disrupted.
Disruption of a brain communication route
In a 2015, published in the magazine JAMA Neurology and led by Davinia Fernández, the following finding is detailed that explains the psychologist’s statement: the existence of structural damage in the communication between the primary motor cortex and the thalamus in people in a coma.
We must keep in mind that the primary motor cortex is responsible for planning and executing movements, and that the thalamus is considered “the door to consciousness.” This communication channel is essential to understand why some patients in a vegetative state are aware of their surroundings, as Fernández-Espejo stated, despite their comatose state and their inability to respond.
Why can’t people in a coma respond to stimuli?
The thalamus is a structure that is also considered “the receptor of the brain.” Sensations that come from all the senses (except smell) pass through it. In turn, it acts as a repeater station, where the relevant signals are selected. For example, in repetitive signals, the transmission is interrupted (such as when we wear a ring for many hours and we no longer perceive its friction).
Instead, we do pay attention to the relevant signals, which are sent to the cerebral cortex (the most evolved area of the brain). This area is responsible for issuing a response, which in turn is returned back to the thalamus, which is in charge of executing it.
But what happens in people in a coma? That there is damage to the pathways that physically connect the thalamus, one of the centers of our consciousness, and the motor cortex, which drives voluntary muscular activity. And therefore, the person in a coma cannot respond to stimuli and therefore cannot move.
Testimony of a person who came out of a coma
The newspaper includes the testimony of a woman who suffered a car accident in 2011 and was induced into a coma by a group of expert doctors, with the aim of stabilizing her and saving her life.
This woman stated that she experienced the coma as a diffuse and blurry event, in which her mind could not form concrete thoughts or dreams. However, she explains that she was capable of perceiving pain and forming memories or “memories” so that her brain could make sense of what was happening around her.
The woman also explained that she was able to recognize her husband’s voice when he entered the room, but that she could not understand what he was saying.
On the other hand, she also described strange episodes: for example, the belief or sensation of being raped during that comatose state, and she could feel anal and vaginal pain. However, that diffuse memory actually had to do with surgical interventions to which she was subjected.
She also claimed to be able to feel temperature changes when she was moved between rooms. She also described nightmares that intermingled in a continuous state between wakefulness and sleep.
What science says
What does science say about what people who have gone through a coma describe? To first analyze this state, a series of parameters are taken into account and the person’s brain responses are quantified using sophisticated techniques.
Regarding the parameters, for example the metabolism of gray mass is analyzed; It has been observed how in patients in hypoxic coma this is 50-70% below normal.
On the other hand, in a 2005 study, for example, a significant difference was found in the patient’s brain reaction to the utterance of unknown and known words. That is, his brain reacted or “activated” to the familiar words, as if he were really “hearing” them. Thus, what the study suggests is that the person (or their brain) could be maintaining a certain semantic perception.
In another article, this time from 2019, led by Kotchoubey, researchers found that the electrical activity of the brains of 104 coma patients was similar to that of an ordinary person receiving an instruction.
Bibliographic references:
- Davinia Fernández-Espejo, PhD. (2015). A Thalamocortical Mechanism for the Absence of Overt Motor Behavior in Covertly Aware Patients. JAMA Neurol, 72(12):1442-1450. doi:10.1001/jamaneurol.2015.2614
- Kotchoubey, B., Daltrozzo, J., Wioland, N., Mutschler, V., Lutun, P., Birbaumer, N., & Jaeger, A. (2005). Semantic processing in a coma patient. Grand Rounds, 5: 37-41.