Quantitative and Qualitative Disorders of Consciousness, Evaluation of the state of consciousness in children and adults, Brainstem reflexes

The human dimension of consciousness is conditioned by wakefulness. Wakefulness is the optimal state of the CNS in which a person can adequately respond to changes in the external environment.

Neurophysiologically, wakefulness is maintained by the reticular formation, specifically the ARAS — an integrative network of nonspecific ascending pathways that relay peripheral stimuli to the brainstem, diencephalon, and cortex to keep the brain activated.

Psychiatric definition of consciousness is that it is the ability to be aware of oneself as an individual in contrast to the surrounding world; the ability to correctly interpret one’s own experiences.

Quantitative Disorders

If wakefulness is impaired, it results in a quantitative disorder of consciousness.

They arise from lesions of the ARAS.

From a time perspective, they are classified as long-term or short-term.

Short-term

Syncope

Short-lasting loss of consciousness that can acutely endanger life (e.g., while driving or falling from height).

It is caused by global cerebral hypoperfusion, with a sudden onset and a loss of postural tone and rapid spontaneous recovery within seconds to a few minutes. The patient often does not recall the event.

Etiological classification:

1. Reflex syncope
   • Vasovagal: disrupted autonomic regulation → parasympathetic dominance → bradycardia + hypotension; typical during prolonged standing in heat.
   • Carotid sinus syndrome: bradycardia + hypotension triggered by pressure on the carotid sinus (e.g., tight collars).
2. Orthostatic syncope
   • Due to insufficient vasoconstriction after standing up quickly; occurs in older adults, patients on antihypertensives, and people with alcohol misuse.
3. Cardiac syncope
   • Caused by arrhythmias or structural heart disease.
4. Other causes
   • Neurological, oncological, or metabolic conditions.

Epileptic seizure

An epileptic seizure is a sudden, short-lasting burst of abnormal electrical activity in the brain. It usually causes a brief blackout, confusion, and sometimes incontinence, followed by a gradual return to normal.

It can be due to an irritative lesion like a scar, tumor, or inflammation.

Metabolic diseases

Conditions that don’t resolve on their own—like hypoxia, hypoxemia, or hypoglycemia—can prolong impaired consciousness. Hypoglycemia causes CNS suppression from lack of fuel and symptoms from catecholamine release.

Infants show irritability, feeding issues, pallor, hypotonia, hypothermia, apneas, bradycardia, reduced consciousness, and seizures; older children show confusion, irritability, tremor, pallor, sweating, tachycardia, weakness, seizures, and coma.

Long-term, early-life or recurrent severe hypoglycemia can cause neurological impairment and secondary epilepsy, with MRI often showing poor gyrification, reduced myelination, and cortical atrophy.

Long-term

Somnolence

State of increased sleepiness. The patient has little spontaneous activity but controls sphincters. Reacts to verbal stimuli.

Sopor

Deep sleep from which the patient can be awakened by painful stimuli. Sphincter control is lost.

Coma

The most severe impairment of consciousness. Basic reflexes fade; e.g., pupils stop reacting to light. No sphincter control. Respiratory and circulatory disturbances appear.

• Lighter coma – mydriasis, mild light reaction
• Deeper coma – miosis
• Deepest coma – paralytic mydriasis without reaction

Brain Death

Occurs when there is a complete, irreversible loss of all brain functions. Spontaneous breathing ceases, light and pain responses are absent. Brainstem reflexes are abolished. Angiography shows cessation of cerebral circulation.

Brain death is considered the death of the individual. It allows termination of resuscitation and the use of suitable organs for transplantation, following strict criteria (expert committee, determination of cause of coma, angiographic findings, etc.).

Apallic Syndrome (Persistent Vegetative State)

Severe cortico-subcortical lesion with preserved brainstem function. Brainstem reflexes including breathing remain intact. Eyes may follow surroundings reflexively, but the patient is unaware. No cognitive functions.

Most often due to global cerebral hypoxia and diffuse axonal injury. Usually irreversible, however in some cases slight improvement occurs.

Locked-in Syndrome

Loss of motor function due to interruption of corticospinal and corticobulbar tracts. Consciousness is preserved, and the patient may be fully lucid. In classic form, the patient can blink and perform vertical eye movements.

Qualitative Disorders

Wakefulness is mostly preserved, but some psychological functions are altered. Disturbances in perception, thinking, emotions, memory and behavior occur.

Obnubilation (clouded consciousness)

A state in which the person remains oriented and can perform some learned, automatic motor routines, but these actions are purposeless, and overall behavior is altered. Awareness is dulled and responses are slowed, but basic orientation is still present.

Delirium (acute confusional state)

Characterized by a sudden loss of time and spatial orientation, accompanied by hallucinations, vivid dream-like experiences, and fluctuating attention. The person may appear agitated, frightened, or confused, and their perception of reality is distorted.

Amentia (confusion)

Similar to delirium but without hallucinations. It features anxiety, helplessness, incoherent or fragmented thinking, and moments of near-normal clarity alternating with deep confusion. Disorientation is broad:

• Autopsychic (not knowing who they are)
• Allopsychic (not knowing where they are)
• Time disorientation (not knowing what time it is)

4. Somnambulism (sleepwalking)

An incomplete awakening from non-REM sleep, during which the person can walk or perform simple actions with a vacant expression. Behavior is automatic, poorly coordinated, and not consciously controlled. After awakening, the person typically has no memory of the event.

Glasgow Coma Scale

The Glasgow Coma Scale (GCS) is a widely used clinical tool for assessing a patient’s level of consciousness, particularly after head injury or in any condition involving altered mental status.

It provides a standardized way to evaluate brain function based on three observable components:

• eye opening
• verbal response - evaluates orientation and coherence of speech
• motor response

Each component is scored separately, and the sum which is the GCS score ranges from 3 to 15.

Eye opening

	Adults	Children
1	no response	no response
2	to pain	to pain
3	to speech	to speech
4	spontaneous	spontaneous

Verbal response

	Adults	Children
1	no response	no sounds
2	incomprehensible sounds	moans or grunts to pain
3	inappropriate words	cries to pain
4	confused conversation	irritable, crying spontaneously
5	oriented	coos, babbles, interacts

Motor response

	Adults	Children
1	no response	no response
2	extension (decerebrate)	extension (decerebrate)
3	abnormal flexion (decorticate)	abnormal flexion (decorticate)
4	withdraws from pain	withdraws from pain
5	localizes pain	localizes pain
6	obeys commands	obeys commands

The total score (GCS score) classifies the severity of impairment:

13–15: mild injury or minor impairment

9–12: moderate impairment

3–8: severe impairment or coma

Brainstem Reflexes

Brainstem reflexes help determine whether the brainstem is functioning in an unconscious patient.

If they are present, the cause of coma is often above the brainstem. If they are absent, it suggests brainstem damage, which is associated with deeper coma and a worse prognosis.

Oculocephalic Reflex (“Doll’s eye”)

Positive oculocephalic reflex

The unconscious patient’s head is gently turned side to side (only if we suspect the cervical spine is not injured!!).

Normal: the eyes move opposite the head turn → brainstem intact.

Abnormal: the eyes move with the head → brainstem lesion.

Oculovestibular reflex

Oculovestibular Reflex (Caloric test)

Cold water is instilled into the ear canal with the head elevated 30°.

Normal: the eyes deviate toward the irrigated side → intact vestibular and brainstem pathways.

Abnormal: no eye movement → brainstem dysfunction.

References

1. STAŇKOVÁ, M. České ošetřovatelství 6 – Hodnocení a měřící techniky v ošetřovatelské praxi. 1. vydání. Brno : Institut pro další vzdělávání pracovníků ve zdravotnictví, 2000.
2. AMBLER, Zdeněk. Základy neurologie. 6. vydání. Praha : Galén, 2006.
3. Disorders of Consciousness [online]. Medlink; [cit. 7. 12. 2025]. Link: https://www.medlink.com/articles/disorders-of-consciousness