Loss of Consciousness

When something interferes with interactions in the brain that allow awareness, a person’s level of consciousness can change in several ways. Altered level of consciousness (ALC) is among the most common problems seen in medicine. Studies estimate that up to 5% of emergency room admissions in urban hospitals are related to disorders of consciousness.

Consciousness can be measured on a spectrum that ranges from full wakefulness to deep coma.

Altered levels of consciousness include the following conditions:

  • Confusion: A confused person cannot properly process all the information from their surroundings. Apathy and drowsiness are the most noticeable symptoms. The person may be disoriented, especially to time. A severely confused person is usually unable to carry out more than a few simple commands.
  • Delirium: This is a common and complicated problem, especially in the elderly. The signs of delirium include disorientation, which may be total. People with delirium may not remember who they are, or may have delusions and hallucinations. People with delirium may also become drowsy or less alert at times.
  • Obtundation: A lower level of alertness typically characterizes this state. A person in this state often sleeps much more than usual, and when awakened, remains drowsy and confused. Wakefulness can only be maintained by continuously talking to the person, or through constant painful stimulation.
  • Stupor: Stupor is characterized by unresponsiveness from which a person can be aroused only by vigorous and repeated painful stimulation.
  • Coma: A person in a coma appears to be asleep, but cannot be awakened. Oftentimes reflexes are absent, and the legs and arms may be rigid. The respiration rate of someone in a coma is usually slowed.


Trauma to the brain can cause impaired consciousness. Traumatic brain injury (TBI) is the leading cause of death and disability in young adults in the U.S. Several types of head trauma may cause TBI. For example, a closed head injury – the most common TBI – can result if the head rapidly accelerates or decelerates, causing the brain to move through the fluid in the skull and strike the inside of the skull. Other causes include direct impact on the head or penetration by a foreign object such as a bullet.

Infections are a common cause of impaired consciousness. The inflammation that accompanies infection is responsible for ALC. Encephalitis and meningitis are two nervous system-specific infections that can cause ALC.

Defects in the metabolic system can lead to waste build-up that can cause altered levels of consciousness (ALC). As the body goes about the normal processes needed to keep us alive, chemicals and other by-products are produced. In most cases, byproducts get into the bloodstream and are filtered by the liver, kidneys, and other organs. If one of these systems fails, waste products can build-up and act as a poison that interferes with the brain’s ability to function. The insulin/sugar imbalance of diabetes, for example, is a major metabolic problem that can cause impaired consciousness. Diabetics with low blood insulin levels produce ketones, a toxic by-product of fat metabolism. Conversely, when there is too much insulin, cells begin to starve to death. Either case can result in ALC.

Drug exposure is a common cause for ALC. Drug-induced ALC can result from an overdose of either over-the-counter or illegal drugs. Alcohol intoxication is probably the most common cause of drug-induced ALC. Similarly, exposure to certain readily available home or industrial chemicals can lead to changes in consciousness or even to death.

Structural abnormalities of the brain can lead to ALC [Figure 1]. Tumors (benign or cancerous) can form and crowd out the normal structures of the brain. As a result, weakness in the walls of the blood vessels in the brain (aneurysms) may begin to swell, or may even break, causing blood to pool inside the head and push the brain against the bony wall of the skull. The resulting damage can then cause ALC.

Figure 1. MRI Scan Showing a Brain Tumor

When tumors crowd out the normal structures of the brain, they can cause aneurysms that may rupture. A ruptured aneurysm causes blood to pool inside the head, pushing the brain against the bony wall of the skull. The resulting damage can then cause ALC.


The symptoms of ALC are varied. Initial signs of ALC can be as subtle as slurring words while talking, or as severe as death. ALC can present as any of the levels of consciousness, from confusion to stupor to coma.

Symptoms accompanying ALC provide clues to the underlying cause [Table 1]. For example, if a person with ALC also has a tongue that is bitten or scarred, a doctor would suspect that epilepsy is the underlying cause. Likewise, if the person with ALC also has neck stiffness, the doctor may suspect that meningitis is the cause.

Table 1. Possible Causes of ALC by Accompanying Symptom or Sign

System or region Symptom Possible cause(s)
Vital signs Hypertension Cerebral hemorrhage, hypertensive encephalopathy, increased intracranial pr=
essure, renal or endocrine disorder
Hypotension Ethanol or sedative drug toxicity, blood loss, diabetic coma
Hyperthermia Systemic infection, heat stroke, withdrawal from alcohol or drugs
Hypothermia Ethanol or barbiturate toxicity, shock, extracellular fluid deficit
Bradycardia Heart block, Stokes-Adams syndrome, increased intracranial pressure, hypothyroidism
Tachycardia Arrhythmia associated hypoxemia; atrial fibrillation associated with cerebral embolism
Breath Peculiar odor Alcohol ingestion, hepatic failure, ketoacidosis, or uremia
Skin Jaundice Hepatic disorder
Needle-tracks Drug overdose
Rashes Infectious disease, drug reaction, autoimmune disease, pellagra, thrombotic thrombocytopenic purpura
Pallor Hemorrhage (internal or external)
Head Localized tenderness, hematoma, crepitus Skull fracture
Hemorrhage from ears or nostrils; hematoma, tenderness, or crepitus over mastoid process Basilar skull fracture
Face and conjunctiva hyperemic Alcohol intoxication
Tongue bitten or scarred Epilepsy
Neck Stiffness Suggests meningitis/encephalitis, trauma, or subarachnoid hemorrhage

Risk Factors

Certain causes of ALC are more common in particular groups of individuals. Traumatic brain injury is the leading cause of death and disability in those under 45 years of age, while metabolic problems, which can also cause ALC, occur most often in middle-aged and older people.


Urgent Care
ALC is a medical emergency. As there is usually nothing an onlooker can do to treat the cause, the best advice is to call 911 and get the person to the hospital as soon as possible. It should be remembered, however, that even minor changes such as slurring words or unsteadiness could be an early sign of impending problems that should beinvestigated. Do not wait for the person to – pass out – before seeking medicalcare.

After contacting the ambulance, there are some things that can be done to help keep the person safe until help arrives. For example, if the person does not respond when you shake them or yell their name, check to make sure they are still breathing, and that they have a pulse. If they do not, begin cardiopulmonary resuscitation (CPR).If you do not know CPR, an ambulance dispatcher can talk you through the procedure over the telephone. If heat stroke is a possibility, get the person into the shade or an air-conditioned area immediately. If there is ice available (or even cold soft drink cans), place it in the groin area and under the neck. If you know that the probable cause of ALC is type II diabetes, provide the person with sugar as soon as possible. The best way to provide this sugar is through a paste that can be applied to the gums (called Glucagon, among other things). If this paste is not available, regular table sugar can also be placed under the lips and against the gums. The blood vessels in this area are very close to the surface, and readily absorb the sugar, getting it into the blood system and to the brain very quickly. If the person is having a seizure, do not touch them unless it is absolutely necessary to help them avoid injury. If possible, open their collar, remove ties or other constricting things from around the neck and unbutton their shirt. Never try to force anything into the mouth. Remove from the area any objects such as chairs or tables that the person might strike, thereby further injuring themselves. Do not attempt to restrain the person in any way. When the seizure has stopped, place the person on their side in the recovery position. Look around the area for any pill or chemical containers.This will give the healthcare team valuable clues about overdose, poisoning, or medication interaction as cause for the ALC.

Surgery is used to relieve pressure in the brain from a developing mass. A growing mass, which can take many forms (i.e., bleeding from a stroke or aneurysm, abscess from an infection, a tumor or swelling related to trauma), can press on the brain and cause ALC. If this is the case, your doctor will order surgery to remove the offending mass.

If surgery is necessary, a craniotomy will most likely be done. A craniotomy is a surgical method of cutting open the skull to gain access to the brain. After anesthesia is given and the patient is asleep, the surgeon will cut a flap in the skin to expose the bone of the skull. They will then usually drill a number of holes is the skull and use a specialized saw to connect them. The bone flap is then removed, exposing the brain. What happens next will depend on the underlying cause of ALC. If it is an aneurysm, then it may either be clipped, or a special reinforcing fabric will be placed around it to keep it from getting bigger. If the cause is bleeding into the brain or abscess, the surgical team will remove it from the area. In other cases, a tumor may be removed.

Following surgery, the patient is usually admitted to an intensive care unit where vital signs and pressure inside the skull can beclosely monitored. Medications are usually given to limit the chance for infection and seizures after surgery. The person will also be watched closely for changes in level of consciousness and weakness or loss of speech that often signal problems. Frequently the person will only stay in the ICU for about 24 hours. Depending on the outcome, the person may be released home or sent to are habilitation hospital for further treatment.