Consciousness is a complex and multifaceted aspect of human experience. It involves awareness of oneself and the environment, the ability to perceive sensations, emotions, thoughts, and to have subjective experiences. Impairment of consciousness can occur due to various factors such as injury, illness, or medical conditions affecting the brain.
The reticular formation is a complex network of nuclei and nerve fibers located in the brainstem, playing a crucial role in regulating consciousness, arousal, and attention. It’s involved in various essential functions, including sleep-awake transitions, filtering sensory information, and maintaining alertness.
One of its primary roles in consciousness lies in its involvement in the reticular activating system (RAS), which helps control the sleep-wake cycle and overall arousal levels. The RAS receives input from various sensory pathways and sends projections to the thalamus and cerebral cortex, influencing the level of alertness and awareness.
Levels of Consciousness: Neurologists often evaluate consciousness in terms of different levels, ranging from full wakefulness to various states of altered consciousness. These might include:
• Alertness: The ability to stay awake and attentive.
• Arousal: The ability to respond to stimuli.
• Awareness: The capacity to perceive and understand the environment.
States of Consciousness Disorders: Neurology deals with various disorders that can affect consciousness, such as:
• Coma: A state of unresponsiveness where a person cannot be awakened and does not respond to stimuli.
• Vegetative State (Unresponsive Wakefulness Syndrome): The person is awake but not aware, showing no signs of consciousness.
• Minimally Conscious State: A condition where there are minimal but definite behavioral signs of consciousness, such as intermittent response to stimuli.
• Locked-In Syndrome: The individual is conscious and aware but unable to move or communicate verbally due to complete paralysis, often with intact cognitive function.
The most common cause of Locked-In Syndrome is damage to the ventral part of the pons, often resulting from: stroke, trauma, or tumors. The damage disrupts the pathways that allow the brain to send signals to the muscles for voluntary movement which results in central quadriplegia and pseudobulbar palsy. Only some eye movements and blinking are preserved.
Glasgow Coma Scale (GCS): Widely used to assess consciousness in patients with traumatic brain injury. It evaluates eye, verbal, and motor responses to stimuli using a point system ranging from 15-3 points (it can never be less than 3 or 0!)
Eye Opening (E): Assesses the patient’s ability to open their eyes spontaneously or in response to stimuli.
Score: Ranges from 4 (spontaneous eye opening) to 1 (no eye opening).
Verbal Response (V): Evaluates the patient’s verbal interactions and responses.
Score: Ranges from 5 (oriented and converses normally) to 1 (no verbal response).
Motor Response (M): Assesses the patient’s motor abilities or responses to commands.
Score: Ranges from 6 (obeys commands) to 1 (no motor response).
|
Glasgow Coma Scale |
||
|
Response |
Score |
Description |
|
Eye Opening |
4 points |
Eyes open Spontaneously |
|
3 points |
Eyes open to speech |
|
|
2 points |
Eyes open to pain |
|
|
1 point |
No response |
|
|
Verbal Response |
5 points |
Oriented |
|
4 points |
Confused |
|
|
3 points |
Inappropriate words |
|
|
2 points |
Incomprehensible sounds |
|
|
1 point |
No verbal response |
|
|
Motor Response |
6 points |
Obeys commands |
|
5 points |
Purposeful movement to painful stimulus |
|
|
4 points |
Withdraws from pain |
|
|
3 points |
Abnormal flexion to pain (decorticate) |
|
|
2 points |
Abnormal extension to pain (decerebrate) |
|
|
1 point |
No motor response |
|
*Remember mnemonic for calculation: eyes – 4 letters (4 points max score), voice – 5 letters (5 points max score), motion – 6 letters (6 points max score)
Delirium refers to a sudden and severe disturbance in mental abilities that results in confused thinking and reduced awareness of the environment. It’s often a symptom of an underlying medical condition, a side effect of medication or can be seen as a post-surgery complication. Elderly individuals have a high risk of developing delirium. Symptoms can vary but commonly include:
· Reduced awareness of the environment: The person might seem disoriented or have difficulty paying attention to their surroundings.
· Difficulty focusing or maintaining attention: They may struggle to stay focused on a conversation or task.
· Altered thinking: Delirium can cause confusion, disorientation, and difficulty organizing thoughts.
· Emotional disturbances: Patients might experience agitation, irritability, or even hallucinations.
Managing delirium involves addressing its underlying causes and providing supportive care. Some approaches include:
· Identifying and treating the underlying cause: This could involve addressing infections, adjusting medications, correcting dehydration, or electrolyte imbalances.
· Creating a calm environment: Can help reduce agitation and confusion.
· Reorientation techniques: Gentle reminders about the time, place, and situation
· Medication: These are usually short-term and carefully administered.
· Involving family and caregivers.
Brain death
Brain death, on the other hand, is a complete and irreversible loss of brain function. It’s a state where there’s no longer any activity in the brain, including the brainstem. This condition is typically diagnosed by medical professionals through specific criteria:
· Unresponsive Coma: The patient must be in a deep coma and completely unresponsive to all stimuli, including pain, auditory, visual, and other forms of stimulation.
· Cause of Coma Known and Irreversible: This could be due to severe brain injury, trauma, hypoxia (lack of oxygen), stroke, or another extensive brain-related issue that is known to be irreversible.
· Absence of Brainstem Function: This is confirmed through a series of tests that assess the absence of:
· Pupillary response to light
· Vestibulo-ocular reflex (caloric reflex test)
· Corneal reflex
· Gag reflex
· Facial movements to pain
· Apnea Test: This test confirms the absence of brainstem function controlling breathing. It involves temporarily disconnecting the patient from the ventilator and observing if they can initiate breathing on their own.
· Repeat Examinations: The criteria for brain death usually require that these clinical tests confirming the absence of brain function be performed at two separate time points by different physicians, typically with a gap of several hours in between. This helps ensure accuracy and reduces the chance of error.
· Exclusion of Reversible Conditions: such as drug intoxication, severe hypothermia, or certain metabolic disorders that can mimic brain death.
· Documentation and Reporting
EEG in brain death. In brain death, the EEG typically shows a complete absence of electrical activity in the brain. This means a flat or isoelectric EEG, indicating no measurable brain waves. This absence of brain activity persists across all areas of the brain, including the cortex, which is responsible for conscious awareness and higher brain functions.
Reflexes in brain death. In brain death, reflexes that are controlled by the brainstem often cease to function. Medical professionals typically assess several brainstem reflexes as part of the clinical evaluation to confirm brain death. These reflexes include:
· Pupillary reflex: Lack of response to light. In brain death, the pupils are typically fixed and dilated and do not respond to light.
· Corneal reflex: Absence of a blink response when the cornea (the clear covering of the eye) is touched with a cotton swab or a puff of air.
· Oculocephalic reflex (doll’s eyes reflex): When the head is turned to one side, the eyes normally move in the opposite direction. In brain death, this reflex is typically absent, and the eyes remain fixed in position.
· Oculovestibular reflex (cold caloric reflex): In this test, cold water or air is gently introduced into the ear canal, which normally causes the eyes to move in a specific pattern. In brain death, there is typically no eye movement in response to this stimulation.
· Gag reflex: Absence of a gag response when the back of the throat is stimulated. However, this reflex alone is not enough to confirm brain death as it can be affected by other factors.
Verified by Dr. Petya Stefanova
