There is a wide variety of pathologies that can arise from an injury to the human brain. One of the effects that these disorders can have is the decrease of the level of consciousness .

Next we’ll look at the different degrees to which a person can lose consciousness because of a pathology, and why this is thought to occur. However, before speaking properly of this type of decrease and therefore the appearance of disorders, it is important to establish that we understand consciousness to mean.

What do we mean by conscience?

The capacity that allows us to obtain knowledge of ourselves and the environment around us is called consciousness. And the degree a person can have of it will be determined by what he or she does or does not do in a neuronal system known as reticular formation, which is distributed throughout the brainstem, diencephalon and hemispheres of the brain.

Through the Ascending Reticular Activating System (SARA), the reticular formation controls the activity of the cortical and thalamic neurons , being this the key for the existence of vigilance (being awake), all thanks to the bidirectional stimulation between the cortical and reticular areas.

Levels of loss of consciousness

There are different phases with respect to loss of consciousness , some of which are more fatal than others. Let’s review them:

1. Confusion

In this phase the damage is relatively slight , although the person cannot reason quickly and clearly and thinking is slow.

2. Obnubation

In this state the person is sleepy, and even falls asleep , even though this is not the right time or place. When they are awake, they are unable to stay alert, and their movements are very restricted. She can wake up when she comes into contact with stimuli, and is able to react to verbal or painful stimulation.

3. Stupor or semi-comma

Here the individual affected by the accident or pathology can only be awakened if he is presented with repetitive and intense stimuli , but the responses he produces will not be coherent and will be slowed down. When he encounters painful stimuli, he confronts them by avoiding them. There is no sphincter control and no motor activity.

4. The coma

Etymologically, coma means deep sleep. It is a pathological state that presents a great loss in the level of consciousness, it is identified as a stage in which the individual cannot feel or wake up, does not produce any verbal or motor response to external stimuli, however penetrating and painful they may be.

It should be noted that, in a coma, what causes loss of consciousness is the result of the brain not being supplied with blood for 20 or more seconds , or when blood perfusion is below 35ml/minute per 100 grams of brain mass. A physiological saving state is entered, so the brain seeks to reduce energy consumption (use less glucose, for example) to avoid further damage to brain cells

5. Brain death

It is the last phase with respect to loss of consciousness, in this case there is no record of brain activity or in the brain stem, as there is a global infarction and total paralysis of cerebral blood flow. Breathing is suspended (apnea), and can only be maintained by artificial means.

Pathologies that cause them

This type of disorder can arise from many different causes . For example, as a result of a head injury, vascular disorder, brain tumor, epilepsy, excessive consumption of alcohol and a very long etcetera.

Fundamentally, any disease or accident with the potential to damage the diencephalon or brain stem is very likely to result in coma or brain death, while less severe degrees of unconsciousness may be caused by more superficial injuries.

Some patients remain in a coma for weeks, months and even years, and enter a state known as a vegetative state , which is characterised by the fact that the autonomous functions such as heart rate, breathing, temperature regulation and blood pressure are preserved, but not the reasoning, behaviour or voluntary interaction towards the outside world.

Bibliographic references:

  • Antonio, P. P. (2010). Introduction to Neuropsychology. Madrid: McGraw-Hill.