Loss of Consciousness


Loss of consciousness (LOC) is a common medical situation and majority of these patients are brought to the emergency room and then may get admitted to the hospital. A neurologist is frequently called upon to evaluate & manage these patients.

LOC itself is not a disease, it is only the symptom (manifestation) of an underlying disease process.

This condition is not necessarily neurological, several non-neurologial conditions as mentioned below also can manifest with LOC.

The term is used when there is a total unresponsiveness to verbal and many other stimuli. Term coma is preferred when somebody is deeply unconscious.

The multitude conditions that can present with LOC include;

• Fainting (syncope)
• Seizures
• Strokes (especially the posterior circulation)
• Infections (meningitis, encephalitis)
• Raised ICP (intracranial pressure)
• Head Injuries
• Medication induced
• Toxin induced
• Metabolic/endocrine/electrolyte related
• Psychogenic (e.g. conversion disorder, factitious, malingering etc)

More details


The LOC associated with syncope is usually brief, some patients regain consciousness within few seconds as they collapse on to the ground.


Seizure related LOC is seen with generalized seizures. It could be primary or secondary generalized seizures. In addition to being unconscious during the actual seizure episode, many of these patients go into a state called as post-ictal condition where patients continue to be either unconscious or confused. It may last for several minutes to hours, very rarely even days.


With the strokes it is the posterior circulation episodes that may be associated with LOC. There are two pairs of artery supply to the brain; the carotid arteries are in the front and the vertebrobasilar arteries lie in the posterior aspect or back aspect of the neck and brain. The brain centers related with maintaining the consciousness are located mainly in the brainstem area and are supplied by posterior circulation, that is why stroke in these areas can cause LOC.


Infections like severe meningitis and/or encephalitis cause brain swelling, raise the ICP and knock somebody out. Encephalitis involving the brainstem can affect the centers regulating the consciousness as well.

Raised ICP:

Raised ICP due to almost any cause can effectuate LOC. Infections already mentioned above. A big stroke in the cerebral hemispheres, strokes of the cerebellum and/or brainstem, obstructive hydrocephalus (abnormally large ventricles with excessive CSF-cerebrospinal fluid) etc all can case LOC.

Head Injuries:

Head injuries like concussion, contusion, epidural, subdural bleeding all can knock somebody out.

Medication side effect:

Medications especially overdose e.g. diazepam, phenobaritone can cause LOC.

Toxin exposure:

Toxins like alcohol intoxication, organophosphorous poisoning can cause LOC.

Metabolic/endocrine/electrolyte abnormalities:

Conditions including severe kidney, liver failure, severe hypothyroid state, diabetes, hyponatremia (low sodium in the blood) all can make somebody present with Loss of consciousness. Coma is generally a preferred term while dealing with some of these conditions.


There are innumerable causes for loss of consciousness including neurological, non-neurological medical, psychiatric etc. If the history gives clues then only a small number of investigations may be necessary otherwise a bunch of tests are generally required to establish the diagnosis. Tests are ordered on case to case basis and usually include the following;

• Blood tests like electrolytes, Liver function tests, ammonia, complete blood count etc
• Urine analysis
• CT or MRI of brain
• Blood and/or urine toxicology screen
• CSF (cerebrospinal fluid) analysis etc.


The general treatment would usually include;

• Hospitalization,
• Stabilization, close monitoring, maintaining blood pressure, pulse etc
• Oxygen supply if needed breathing assistance like ventilator if needed
• Intravenous fluids, glucose, multivitamins, thiamine etc

The specific or definite treatment would depend upon the cause for Loss of Consciousness and usually includes;

• Antibiotics if infection/sepsis is suspected
• Anti epileptic medications if seizures are the cause
• Stroke treatment if that is the cause
• Head injury protocol if that caused the LOC
• If metabolic/electrolyte/endocrine causes are detected they are treated appropriately etc

Loss of Consciousness to Neurology Articles