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How do doctors know if someone is in a coma?

Doctors use a variety of tests and procedures to determine if a patient is in a coma. The main way is by assessing the patient’s level of consciousness using standardized scales such as the Glasgow Coma Scale. Doctors also look for certain physical signs and symptoms to help diagnose a coma. Imaging tests like CT scans and MRIs can also be used to visualize any brain abnormalities or damage that may be causing the coma.

What is a coma?

A coma is a profound state of unconsciousness in which a patient cannot be awakened or respond meaningfully to stimuli. It is a medical emergency that requires prompt treatment and close monitoring. Some key things to know about comas:

– Caused by injury, illness, or other medical condition affecting the brain. Common causes include traumatic brain injury, stroke, lack of oxygen to the brain, seizures, drug overdose, and metabolic disorders.

– Patient is unresponsive even to very strong stimuli like pain, light, or sound. They show no signs of conscious awareness or ability to voluntarily move.

– Eyes remain closed and do not open, even if eyelids are lifted. Pupils may be dilated but do not respond to light.

– Breathing becomes irregular and may require ventilator support. Other reflexes like swallowing, gag, and cough are also impaired.

– Coma is different from brain death where all brain and brain stem functions have irreversibly ceased. Coma patients retain some brain stem reflexes and have potential for recovery.

– Coma usually lasts from 2-4 weeks, though can persist longer depending on cause. Some patients may transition from coma to vegetative state showing only reflex actions.

What are the different levels of unconsciousness?

There are various levels and types of altered consciousness that doctors distinguish between:

– **Alert:** Patient is fully awake, aware, responds to environment.

– **Drowsy/Lethargic:** Patient shows dulled responses but awakens easily.

– **Stupor:** Patient is mostly unresponsive but shows some reaction to stimuli.

– **Coma:** No eye opening, speech, voluntary movements even with strong stimuli. Only basic reflexes remain.

– **Vegetative State:** Prolonged coma state where sleep-wake cycles return but no awareness. May show reflexive behaviors like grunting, yawning.

– **Brain Death:** Irreversible loss of all brain and brain stem function. Confirmed by strict neurological criteria.

How do doctors diagnose a coma?

Doctors use several methods together to determine if a patient is in a coma:

Evaluation of Responsiveness

The doctor first checks for responsiveness by talking to the patient, shouting if needed, and applying stimuli like pressure to the fingernails or sternum. A comatose patient will show no eye opening or verbal/motor response to any of these. The doctor notes whether the patients opens their eyes, speaks, or moves voluntarily on their own or in response.

Physical Exam

A full neurological exam is done to note:

– Breathing pattern and need for respiratory support

– Pupil size and reaction – constriction to light stimulus

– Corneal reflexes – blinking when cornea is touched

– Oculocephalic reflexes – eyes moving when head turned left/right

– Gag, cough, and swallowing reflexes

– Movement in arms and legs – may be decerebrate or decorticate posturing

Glasgow Coma Scale

The Glasgow Coma Scale (GCS) objectively scores a patient’s level of consciousness based on their verbal, motor, and eye opening responses. Lower scores indicate deeper coma.

Score Eye Opening Verbal Response Motor Response
1 None None None
2 To pain Incomprehensible sounds Extension to pain
3 To speech Inappropriate words Abnormal flexion to pain
4 Spontaneous Confused Flexion/Withdrawal to pain
5 N/A Oriented Localizes to pain
6 N/A N/A Obeys commands

A comatose patient usually scores between 3-8 based on preserved brainstem reflexes. The scale is repeated regularly to track their progress.

Imaging Tests

Tests like CT scans and MRIs provide visualization of the brain and can detect strokes, tumors, blood clots, bleeding, contusions, or other abnormalities that may be causing the coma. Repeated imaging may be needed to follow injury evolution.


Electroencephalography (EEG) measures electrical activity in the brain. It can help identify seizures or encephalopathy as a coma cause and also track brain function. Certain EEG patterns may help predict coma outcomes.

What causes coma?

Causes of coma can be broadly divided into:

Structural Brain Lesions

– Traumatic brain injury – Bleeding, swelling, contusions from blows to the head. Common in car accidents, falls, violence, sports injuries.

– Stroke – Bleeding (hemorrhagic), blood clots (ischemic), or vessel blockages diminishing blood flow and oxygen to brain tissue.

– Brain tumors – Mass effect compressing vital brain structures. Often in frontal, temporal, parietal lobes.

– Infections – Swelling and inflammation of brain tissue due to meningitis, encephalitis, or brain abscess.

– Toxic-metabolic disorders – Liver/kidney failure leading to waste buildup and electrolyte imbalances affecting brain cells.

Functional Causes

– Lack of oxygen – Hypoxia from drowning, cardiac arrest, shock, respiratory failure.

– Seizures – Generalized seizure activity suppressing brain function. Non-convulsive status epilepticus.

– Drug overdose – Sedatives, opioids, alcohol, other toxins.

– Endocrine issues – Thyroid, adrenal or pituitary gland dysfunction altering hormones.

Other Factors

– High fever – Hyperthermia impacting brain cellular function.

– Low blood sugar – Hypoglycemia due to diabetes, malnutrition, alcoholism etc.

– Electrolyte disturbances – Imbalances like hyper/hyponatremia, hyper/hypocalcemia.

– Infections – Sepsis, multiple organ dysfunction exposing brain to toxins.

What happens to the brain during a coma?

The comatose brain is in a state of depressed function due to varied underlying causes. Some key changes occurring:

Diminished Electrical Activity

– The EEG shows slowing and attenuation of normal brain wave patterns.

– In mild coma, alpha and theta waves persist. As coma deepens, only delta waves or electrocerebral silence may remain reflecting cortical inactivation.

– Specific EEG patterns like burst-suppression may indicate structural damage or poor outcome.

Impaired Blood Flow

– Reduced cerebral blood flow from restricted or blocked vessels limits oxygen and nutrients to brain tissue.

– Loss of autoregulation can cause unstable blood pressures, either too high or too low for normal perfusion.

– Brain swelling (edema) may compress microcirculation.

Cellular Dysfunction

– Neurons deplete their energy stores and cannot fire properly.

– Ionic shifts lead to accumulation of calcium, sodium, and glutamate further harming cells.

– Loss of glucose and oxygen supply forces anaerobic metabolism.

– Mitochondrial damage and free radical release lead to apoptosis and cell death.

Metabolic Changes

– Glucose use, ATP production, and oxygen consumption decline up to 40-50%.

– Cerebral glucose levels may be very high or low.

– Lactate rises along with csf glutamate, dopamine, and GABA.

Loss of Connectivity

– Widespread structural disconnections in the cortical and thalamo-cortical circuits.

– Functional connectivity declines between distant brain regions.

– Thalamus gets disconnected from the cortex.

How is a coma treated?

As coma has varied causes, treatment focuses on:

Addressing Underlying Cause

– Reverse hypoxia – Protect airway, give oxygen, ventilate

– Control seizures – Give anticonvulsants

– Lower intracranial pressure – Drain excess csf, hyperventilate, elevate head

– Treat infections – Antibiotics, antivirals

– Remove brain lesions surgically – Clot evacuation, tumor resection

Supportive Medical Care

– Airway/breathing – Intubation, ventilation if needed

– IV fluids and nutrition – Maintain glucose, electrolyte balance

– Bowel/bladder care – Incontinence management

– Skin care – Prevent pressure ulcers

– Physical therapy – Passive range of motion exercises

Monitoring and Prevention

– Vital signs, ICP, cerebral oximetry

– Avoid complications like DVT, pneumonia

– EEG for seizure detection

– Imaging to follow injury evolution

Targeted Therapy

– Neuroprotective agents – Hypothermia, citicoline, albumin

– Stimulants – Amphetamines, zolpidem, amantadine

– Neuromodulation – Vagal nerve, DBS stimulation

What is the outlook for coma patients?

The prognosis for coma patients depends on:


– Traumatic comas have better recovery than non-traumatic

– Structural damage carries worse outlook than toxic-metabolic comas


– Younger patients have better potential for neuronal plasticity

– Chronic illness negatively impacts recovery

Time Unconscious

– Duration over 4 weeks indicates poor prognosis

– Longer comas have higher mortality

Early Signs

– Absent brainstem reflexes predict poor outcome

– Some EEG patterns indicate irreversible damage

Level of Support

– Careful medical management improves outcomes

– Access to rehab services aids recovery


– Following commands signifies termination of coma

– Reaching conscious state within a month prognosticates well

Coma Duration Mortality Rate Favorable Outcome
1 week 10% 87%
2 weeks 17% 69%
1 month 36% 46%
3 months 62% 14%

With dedicated care, 1 in 3 coma patients can have good cognitive recovery. Supportive family involvement also helps. Talking, reading, music may stimulate the patient’s brain even when unresponsive.


Doctors assess coma using clinical evaluation of responses, detailed physical exams, scoring systems, imaging, and EEG. Determining the underlying cause guides appropriate life-supporting and restorative treatments. While coma prognosis depends on multiple factors, patients still stand a fair chance of regaining consciousness with prompt care. Close monitoring and follow-up continue to be critical during the recovery phase. With compassionate support and rehabilitation, some coma survivors can eventually regain their quality of life.