Coma
A deep state of unconsciousness that cannot be reversed by stimulation
Quick Facts
- Type: Neurological emergency
- Common causes: Head injury, stroke, low blood sugar, overdose
- Key sign: Cannot be awakened, no purposeful response
- Action: Call emergency services immediately
Overview
A coma is a state of deep unconsciousness in which a person is alive but cannot be awakened, does not respond to voice or pain in a purposeful way, and has no normal sleep-wake cycles. It reflects serious disruption of the parts of the brain that control awareness and alertness.
A coma is always a medical emergency. It is a symptom of a serious underlying problem rather than a disease on its own. How long it lasts and what happens afterward depend heavily on the cause and how quickly it is treated. Some people recover fully, while others may pass into other states of altered consciousness.
Doctors describe different states of reduced consciousness that a person may move through. A coma is the deepest, with no eye opening and no purposeful response. As some people improve, they may enter a state with sleep-wake cycles but limited awareness, or a state of minimal but real responsiveness. Understanding these stages helps medical teams and families track progress and set realistic expectations during recovery.
Symptoms
A person in a coma shows a profound lack of responsiveness:
- Closed eyes that do not open to voice or touch
- No purposeful movement of the limbs
- No response to spoken words
- Limited or absent reflexes, depending on depth
- Irregular breathing patterns in some cases
- No reaction when spoken to loudly or gently shaken
Before a coma fully develops, a person may show warning signs such as increasing drowsiness, confusion, slurred speech, weakness on one side, severe headache, or repeated vomiting. These changes in alertness should be treated as urgent.
Causes
A coma results from widespread brain dysfunction, which can have many causes:
- Traumatic brain injury: a severe blow to the head from a fall, crash, or assault
- Stroke: bleeding or a blocked artery that deprives the brain of blood
- Lack of oxygen: after cardiac arrest, drowning, or choking
- Blood sugar problems: very low or very high blood sugar in people with diabetes
- Poisoning and overdose: alcohol, opioids, sedatives, or other toxins
- Infections: such as meningitis or encephalitis
- Severe liver or kidney failure, or dangerously low sodium
- Prolonged seizures that do not stop on their own
- Dangerously high or low body temperature
Risk Factors
- Severe head trauma
- Poorly controlled diabetes
- Heart disease or risk of cardiac arrest
- Drug or alcohol misuse
- Severe liver or kidney disease
- Brain infections or untreated severe illness
Diagnosis
Doctors work quickly to find and treat the cause while assessing how deep the coma is.
- Neurological exam: checking response to voice and pain, pupil reactions, reflexes, and breathing
- Glasgow Coma Scale: a scoring system that rates eye, verbal, and movement responses
- Blood tests: for blood sugar, electrolytes, drugs, oxygen levels, and organ function
- Brain imaging: CT or MRI scans to look for injury, bleeding, stroke, or swelling
- Lumbar puncture or EEG: when infection or ongoing seizures are suspected
Treatment
Emergency care focuses first on keeping the person alive and stable, then on reversing the cause.
- Supporting vital functions: protecting the airway, supporting breathing and blood pressure
- Treating the cause: giving glucose for low blood sugar, an antidote for certain overdoses, antibiotics for infection, or surgery for bleeding or pressure on the brain
- Reducing brain swelling: medications or procedures to lower pressure inside the skull
- Ongoing care: nutrition, prevention of bedsores and clots, and physical therapy during recovery
The chance of recovery depends on the cause, the person's age, and how long the brain was affected.
When to See a Doctor
A coma is a life-threatening emergency. Call emergency services immediately if a person cannot be awakened or becomes deeply unresponsive. Also seek emergency care for warning signs that can come before a coma:
- Sudden severe headache, confusion, or slurred speech
- Weakness or numbness on one side of the body
- Repeated vomiting with drowsiness after a head injury
- Known diabetes with extreme drowsiness
- Suspected overdose or poisoning
While waiting for help, keep the airway clear and place the person on their side if they are breathing. Do not give them anything to eat or drink, and tell responders about any recent injury, illness, medications, diabetes, or possible poisoning, as this information can speed up the right treatment.
Frequently Asked Questions
Is a coma the same as being asleep?
No. A sleeping person can be awakened by sound, touch, or pain, but a person in a coma cannot. A coma reflects serious brain dysfunction and is always a medical emergency requiring immediate care.
What should I do if I cannot wake someone up?
Call emergency services immediately. While waiting, check that they are breathing, gently place them on their side to keep the airway clear, and do not give food or drink. Tell responders about any injury, medications, diabetes, or possible overdose.
Can someone recover from a coma?
Yes, recovery is possible, especially when the cause is treated quickly. Outcomes range from full recovery to lasting effects, depending on the cause, the person's age, and how long the brain was affected. Some people transition into other states of reduced consciousness.
How do doctors measure how serious a coma is?
Doctors often use the Glasgow Coma Scale, which scores eye opening, verbal responses, and movement. A lower score means a deeper level of unconsciousness. They combine this with imaging and blood tests to find the cause.
What are common causes of a coma?
Frequent causes include severe head injury, stroke, lack of oxygen after cardiac arrest, very high or low blood sugar, drug or alcohol overdose, and serious infections such as meningitis. Liver or kidney failure can also be responsible.
References
- National Institute of Neurological Disorders and Stroke (NINDS). Coma.
- Mayo Clinic. Coma - Symptoms and causes.
- MedlinePlus, U.S. National Library of Medicine. Coma.
- Cleveland Clinic. Coma.