Cortical death - 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.

Coma

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.

Read more about comas.

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.

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.

Read more about how states of impaired consciousness are diagnosed.