Impaired consciousness

12 min read

What is impaired consciousness?

A disorder of consciousness, or impaired conciousness, is a state where consciousness is affected by an injury to the brain.

Consciousness refers to both wakefulness and awareness. Wakefulness is the ability to open your eyes and have basic reflexes, such as coughing, swallowing and sucking. Awareness is associated with more complex thoughts and actions, such as following instructions, remembering, planning and communicating.

There are several different states of impaired consciousness, depending on how these abilities are affected. These include:

  • coma
    – when there are no signs of wakefulness or awareness
  • vegetative state – when a person is awake but showing no signs of awareness
  • minimally conscious state – when there is clear but minimal evidence of awareness that comes and goes

Read more about the

features of disorders of consciousness

Why they happen

Disorders of consciousness can occur if the parts of the brain involved with consciousness are damaged. These types of brain injury can be divided into:

  • traumatic brain injury – the result of a
    severe head injury
    , such as that sustained during a car accident or a fall from a great height
  • non-traumatic brain injury – where the injury to the brain is caused by a health condition such as a
  • progressive brain damage – where the brain is gradually damaged over time, for example due to
    Alzheimer's disease

Read more about the

causes of disorders of consciousness

Making a diagnosis

A disorder of consciousness will only be confirmed after extensive testing to determine levels of wakefulness and awareness. These examinations need to be carried out by someone experienced in disorders of consciousness, although the views of other healthcare professionals and family members will also be taken into consideration.

For some states of impaired consciousness, such as vegetative state, there are recommended criteria to help confirm a diagnosis.

Read more about

diagnosing disorders of consciousness

Treatment and care

Treatment can’t ensure recovery from a state of impaired consciousness. Instead, supportive treatment is used to give the best chance of natural improvement. This can involve:

  • providing nutrition
  • making sure the person is regularly moved so they don't develop pressure ulcers
  • gently exercising their joints to prevent these from becoming tight

In some cases, a treatment called sensory stimulation may be used in an attempt to increase responsiveness. This involves stimulating the main senses, such as vision, hearing and smell. For example, a person’s favourite song may be played to stimulate their hearing. However, it’s not entirely certain how effective this treatment is.

If health professionals and family members agree there is no point in continuing treatment, the decision usually has to be referred to the courts before treatment can be withdrawn. This would usually be considered if a person was in a state of impaired consciousness for at least 12 months, as the chance of recovery by this point are remote.

Read more about

treating disorders of consciousness


It’s impossible to predict the chances of someone in a state of impaired consciousness improving. It largely depends on the severity and type of brain injury, the person’s age, and how long they’ve been in a state of impaired consciousness.

Some people improve gradually, whereas others stay in a state of impaired consciousness for years. Many people never recover consciousness.

There are only isolated cases of people recovering consciousness after several years. The few people who do regain consciousness often have severe disabilities caused by the damage to their brain.

Impaired consciousness symptoms

Different disorders of consciousness can be classified by the brain functions affected.

The main disorders of consciousness are outlined below.


A coma is when a person shows no signs of being awake and no signs of being aware. A person in a coma lies with their eyes closed and doesn’t not respond to their environment, such as voices or pain.

A coma usually lasts for less than two to four weeks, during which time a person may wake up or progress into a vegetative state or minimally conscious state.

Read more about


Vegetative state

A vegetative state is when a person is awake but is showing no signs of awareness.

A person in a vegetative state may open their eyes, wake up and fall asleep at regular intervals and have basic reflexes, such as blinking when they are startled by a loud noise or withdrawing their hand when it’s squeezed hard. They are also able to regulate their heartbeat and breathing without assistance.

However, a person in a vegetative state does not show any meaningful responses, such as following an object with their eyes or responding to voices. They will also show no signs of experiencing emotions.

If a person is in a vegetative state for a long time, it may be classified as:

  • a ‘continuing vegetative state’ – where someone is in a vegetative state for longer than four weeks
  • a ‘permanent vegetative state’ – where someone is in a vegetative state for either more than six months (if caused by a non-traumatic brain injury) or more than 12 months (if caused by a traumatic brain injury). See
    causes of impaired consciousness
    for more information about the different types of brain damage.

If a person is diagnosed as being in a permanent vegetative state, recovery is extremely unlikely, but not impossible.

Minimally conscious state

A person who shows clear, but minimal or inconsistent awareness is classified as being in a minimally conscious state. They may have periods where they can communicate or respond to commands, such as moving a finger when asked to do so.

A person may enter a minimally conscious state after being in a coma or vegetative state. In some cases a minimally conscious state is a stage on the route to recovery, but in others it’s permanent.

Like vegetative state, a minimally conscious state may be considered to be ‘continuing’ if it lasts longer than four weeks. However, it is more difficult to diagnose a ‘permanent minimally conscious state’ because it depends on things such as the type and severity of the brain injury and how responsive the person is. In most cases, a minimally conscious state is not usually considered to be permanent until it has lasted for several years.

Read more about

how states of impaired consciousness are diagnosed

Impaired consciousness causes

Disorders of consciousness can occur if the parts of the brain responsible for consciousness are injured or damaged.

The main causes can generally be divided into:

  • traumatic brain injury
  • non-traumatic brain injury
  • progressive brain damage

Common examples of these types of brain damage are outlined below.

Traumatic brain injury

Traumatic brain injury occurs when an object or outside force causes severe trauma to the brain. This is most often due to:

  • falls
  • traffic accidents
  • violent assault


severe head injury
for more information.

Non-traumatic brain injury

Non-traumatic brain damage is usually caused by a health condition such as:

  • a condition that deprives their brain of oxygen, as without a continuous supply of oxygen the tissue that makes up the brain will begin to die
  • a condition that directly attacks the tissue of their brain

Specific causes of non-traumatic brain injury include:

  • strokes
  • heart attacks
  • severe brain infections, such as
    (an infection of the outer layer of the brain) or
    (an infection of the brain itself)
  • drug overdoses
  • poisoning
  • almost drowning or other types of suffocation, such as smoke inhalation
  • a blood vessel bursting leading to bleeding inside the brain – the medical term for this is a ruptured

Progressive brain damage

In some cases, brain damage can gradually occur over time. Examples of conditions that cause progressive brain damage include:

Impaired consciousness diagnosis

It takes extensive testing to assess levels of wakefulness and awareness before a disorder of consciousness can be confirmed.

This may involve tests such as brain scans, but it’s largely based on the specific features a person displays, such as whether they can respond to commands. Read more about the

features of disorders of consciousness

The Glasgow Coma Scale

Doctors can score a person's level of consciousness using a tool called the Glasgow Coma Scale. This assesses three things:

  • eye opening – a score of 1 means the eyes don’t open at all, and 4 means opens eyes spontaneously
  • verbal response to a command – 1 means no response, and 5 means a person is alert and talking
  • voluntary movements in response to a command – 1 means no response, and 6 means a person can follow commands

A lower score indicates a more severely impaired consciousness, such as a

, although this level will be monitored regularly to look for any changes.

The brain injury association, Headway, has more detailed information about the Glasgow Coma Scale.

Brain scans

Brain scans are used to help assess the level of brain damage in someone with impaired consciousness, but can also be helpful in assessing how a person responds to stimulation. This can be especially useful if a person cannot move or speak.

There are several types of scans that can assess brain function, but most commonly a

magnetic resonance imaging (MRI) scan
is used. An MRI scan uses strong magnets and radio waves to create a detailed image of the brain.

Brain scans can show changes if the brain is responding to lights and sound. However, they do not necessarily show awareness because the brain is able to respond to stimulation even without you being aware of it.

Research is being carried out into ways brain scans can be used to show true awareness.

Criteria for a vegetative state

A vegetative state is when a person is awake but showing no signs of awareness. Doctors are particularly careful when diagnosing a permanent vegetative state, as there is a risk of misdiagnosis. A confident diagnosis can only be made if the following criteria have been met:

  • The cause of the brain injury has been established – for example, if a case of
    is suspected then a diagnosis can be confirmed by testing the fluid that surrounds the brain for infection.
  • It has been confirmed that drugs or medication are not responsible for the symptoms.
  • It has been confirmed that treatable problems with the body’s chemistry (a metabolic disorder) are not responsible for the symptoms of loss of awareness – an example of a metabolic disorder is a diabetic coma, where people lose consciousness because their blood sugar levels are either dangerously high or dangerously low.
  • The possibility of a treatable cause in the brain, such as a brain tumour, has been ruled out by brain imaging scans, such as a MRI scan.
  • Examinations have been carried out by a trained assessor experienced in prolonged disorders of consciousness

For a permanent vegetative state to be confirmed, the above criteria must apply and six months must have passed since the start of symptoms after a non-traumatic brain injury, or 12 months after a traumatic brain injury.

Impaired consciousness treatment

Treatment can’t ensure recovery from a state of impaired consciousness, but measures can be taken to increase the chances of natural improvement.

This will usually involve:

  • providing nutritional support through a feeding tube
  • making sure the person is regularly moved so they don't develop pressure ulcers
  • gently exercising their joints to prevent them from becoming tight
  • keeping their skin clean
  • managing their bowel and bladder, such as using a tube known as a catheter to drain the bladder
  • keeping their teeth and mouth clean

Attempts will also be made to reduce the chances of infection, which can be dangerous for someone in a state of impaired consciousness.

Sensory stimulation

A treatment called sensory stimulation may help increase responsiveness in some people with impaired consciousness.

It involves stimulating some of the main senses – touch, hearing, vision and smell – for a short time each day. It’s usually carried out by a trained specialist, but family members are often encouraged to be involved. Some examples of sensory stimulation include:

  • visual – showing photos of friends and family, or a favourite film
  • hearing – talking, or playing a favourite song
  • smell – putting flowers in the room or spraying a favourite perfume
  • touch – holding their hand, or stroking their skin with different fabrics

It’s not entirely clear how effective sensory stimulation is, but it’s sometimes considered worthwhile.

Withdrawing nutritional support

If a person is in a state of impaired consciousness for a long time, usually at least 12 months, it may be recommended that nutritional support is withdrawn. This is because:

  • there is almost no chance of a recovery by this point
  • prolonging life would have no benefit to the individual concerned
  • prolonging treatment would offer only false hope and cause unnecessary emotional distress to the friends and family of the person concerned

The medical team will discuss the issue with family members, and will give them time to consider all the implications.

If the court agrees with the decision, nutritional support will be withdrawn and the person will die peacefully within a few days or weeks.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.