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
Note that people with locked-in syndrome are conscious and aware, but completely paralysed and only able to control eye movement. Learn more about paralysis.
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 an injury 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 stroke
progressive brain damage – where the brain is gradually damaged over time, for example because of Alzheimer's disease
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.
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:
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 by this point the chances of recovery are remote.
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 for.
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.
Being in a coma
Information for anyone whose friend or loved one is in a coma
Features of disorders of consciousness
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 respond to their environment, 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.
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).
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.
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.
As with 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.
Locked-in syndrome has similar features to disorders of conciousness. However, a person with locked-in syndrome is both awake and aware, but they are paralysed and unable to speak.
A person with locked-in syndrome can usually move their eyes and are sometimes able to communicate by blinking.
Causes of disorders of consciousness
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 caused by:
Non-traumatic brain injury
Non-traumatic brain damage is usually caused by a health condition such as:
a condition that deprives the brain of oxygen – without a continuous supply of oxygen, brain tissue will begin to die
a condition that directly attacks brain tissue
Specific causes of non-traumatic brain injury include:
severe brain infections, such as meningitis (an infection of the outer layer of the brain) or encephalitis (an infection of the brain itself)
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 aneurysm
Progressive brain damage
In some cases, brain damage can gradually occur over time. Examples of conditions that cause progressive brain damage include:
a brain tumour
Diagnosing disorders of consciousness
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 is largely based on the specific features a person displays, such as whether they can respond to commands.
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 coma, although this level will be monitored regularly to look for any changes.
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 meningitis is suspected, 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 an 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.
Treating disorders of consciousness
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.
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 agreement is reached about withdrawing life support, the decision has to be referred to the courts in England, Wales and Northern Ireland before any further action can be taken. In Scotland, a court ruling is not required, but is often sought.
If the court agrees with the decision, nutritional support will be withdrawn and the person will die peacefully within a few days or weeks.