Coma and Persistent Vegetative State

A coma is a term that the average man on the street is aware of, but for the most part the word “coma” doesn’t actually provide a lot of helpful information.

The term coma is used to describe the state where an individual is unconscious and not responding to stimuli, and cannot be woken up. They are however very much alive.

This lack of responsiveness can be attributed to a huge number of different causes and it is this which is the most relevant in determining whether a recovery is likely to be made, whether the individual will go into a permanent vegetative state or remain only minimally conscious.

Understanding what a coma is

A coma is the term used for an individual who is unresponsive and still has brain activity, but only minimally so. Although they are alive they will show no indication that they are aware of life going on around them.

The individual’s eyes will be closed, and regardless of what stimuli is introduced, there will be no response. This includes things such as their favourite piece of music, the presence of their loved ones or even pain. Someone in a coma has no way of being able to communicate voluntarily or be able to move at will. Reflex movement may be seen in the limbs; this is not a sign that the coma is lifting. 

The degree of assistance required can vary depending on the cause which led to the coma, and the severity of the coma. Some individuals retain autonomic responses such as breathing, as well as weak reflexes such as coughing or swallowing. Others require intervention to be able to manage these bodily functions.

Diagnosis

It may appear relatively easy to identify a coma but there are a number of specific features which differentiate it from other conditions.

Specifically, the individual will be unconscious but there will be no pupil responses to light, indicating depression of brain stem activity.

As the individual is unable to describe how they are feeling and what transpired beforehand, the doctors will need to take a comprehensive history from those who were close to them before they became unconscious.

The following information could be useful in reaching a diagnosis:

1. Whether the episode was abrupt or whether the loss of consciousness was gradual
2. Any symptoms which were noticeable beforehand
3. Past medical history
4. Drug use, both prescribed and otherwise
5. Potential contributing events, such as any trauma or recent illnesses

In addition to the information supplied by friends and relatives, the doctors will carry out a physical assessment, plus perform some investigations.

The physical exam will include checking reflexes and stimuli, looking for external signs of trauma such as bruising, and observing patterns of breathing.

Pressure may be placed upon various parts of the body, and either warm or icy water squirted into the ears to watch for any responses within the eye. This will help to identify the degree of unconsciousness and potential brain functioning.

The following tests and investigations may also be performed:

1. Blood tests - to check electrolytes, blood count, glucose, organ function, drugs, alcohol and also whether there are any signs of carbon monoxide poisoning
2. Lumbar puncture - to look more closely for signs of infection
3. CT/MRI scans - to establish if bleeding, tumours or ischemic events have caused the coma. The latter is particularly useful in examining deeper structures such as the brain stem
4. EEG - to check whether seizure activity has caused the coma.

Differential diagnosis

When diagnosing a coma it is important to rule out other conditions such as:

1. Brain death. There may be similarities between brain death and coma, particularly when the latter requires life support. However, with brain death the damage is irreversible and all brain function has ceased. A coma may progress to brain death in severe cases, particularly when the brain injury is widespread
2. Locked-in syndrome. This neurological disorder is very rare but paralyses the individual completely, with the sole exception of eye muscles. There is no change to their intellectual function and they remain alert and awake despite being unable to voluntarily speak or move.

Causes

All comas are caused by some kind of injury to the brain; this can result either from disease or from trauma. These brain injuries can either be permanent or temporary; in the case of the latter, as the injury starts to heal, the individual may show signs of recovery.

Over half of comas are linked to disruptions to the circulatory flow within the brain or trauma. Some of the commonest causes of coma include:

1. Trauma. Any kind of injury to the head can cause the brain to bleed and/or swell. This results in the fluid being squashed up against the skull which can then cause downward pressure onto the brain stem, the part of the brain which regulates awareness and arousal via the Reticular Activating System (RAS).
2. Swelling without trauma. In some cases the brain can swell even when there has been no trauma such as when there has been a deprivation of oxygen, an imbalance of electrolytes or the wrong levels of hormones.
3. Bleeding. When bleeding occurs within the tissues within the brain, the side which is affected may swell and become compressed.
4. Stroke. This can prevent the blood flow to parts of the brain stem and when associated with swelling and blood loss, coma can result.
5. Uncontrolled diabetes. Both hyperglycaemia and hypoglycaemia can lead to a coma but unlike other types, this is usually easily resolved when blood sugar levels are corrected.
6. Hypoxia/anoxia. Drowning, choking, or a temporary cessation in cardiac function can all lead to a reduction in the amount of oxygen which reaches the brain.
7. Seizures. Isolated convulsions rarely lead to complications such as a coma but a dangerous condition known as status epilepticus, where seizure are unremitting, can do so. This type of prolonged seizure activity doesn’t provide sufficient time for the brain to recover between episodes, leading to extended periods of unconsciousness or even coma.
8. Toxins. If the body is unable to eliminate poisonous substances they can quickly accumulate to levels which can become toxic. This includes drugs and alcohol, but also can be the result of medical conditions such as asthma (when carbon dioxide builds up), liver disease (an excess of ammonia) and kidney disease (causing urea to accumulate). Toxic-metabolic encephalopathy is an example of this.
9. Infection. When an infection reaches the central nervous system, such as in the case of either meningitis or encephalitis, a coma can result.
10. Tumours. Both benign and malignant tumours can result in a coma, either as a result of invasion into healthy tissue or due to compression.

In some cases a coma may be medically induced deliberately in order to protect the tissues within the brain from the effects of swelling, typically following trauma. This is achieved by administering an anaesthetic which is carefully controlled, rendering the individual unconscious until the doctors believe it is safe for them to be woken. During this period of unconsciousness, their vital signs will be carefully monitored within an ICU.

Monitoring

For the loved ones of an individual in a coma, the hope that they will wake up is ever-present so having some way of judging whether there is any change can be helpful.

A tool known as the Glasgow Coma Scale (GCS) is used to track and assess the level of an individual’s responsiveness and whether there are any signs of change.

The GCS is split into three main areas:

1. Opening of the eyes - scored between 1-4. An individual who cannot open their eyes would score 1, while someone who can open eyes voluntarily would score 4.
2. Verbal responses - no response would score 1, while an individual who was communicative and alert would score top marks of 5
3. Voluntary movements - scoring one means there is no sign of movement in response to a command while the highest mark of 6 means an individual is able to obey a command for movement.

Out of a total maximum score of 15, most individuals in a coma will score 8 or less. The lower the score is, the greater the chance that serious brain damage may have occurred, hampering the chances of recovery.

All functions will be taken care of within an ICU ordinarily, at least in the short term. This enables them to remain under close monitoring, ensuring their condition remains as stable as possible.

If the coma becomes a longer term condition, support may be given on a hospital ward, with healthcare staff responsible for trying to prevent bedsores from developing by moving and turning the individual regularly, providing nutrition, exercising their muscles and joints gently and keeping infections at bay wherever possible. Bladder and urinary infections are a particular risk during a coma.

Awareness during a coma

Although to the observer it may appear that the individual in a coma is not making any responses to either their environment or stimuli, it is as yet unclear the extent of what may be experienced.

Some people who recovery from comas have a clear memory of some of what went on around them, while others have no recollection at all.

Research has suggested that stimulating the individual, particularly smell, vision, hearing and touch could help to promote a recovery.

Therefore, having tactile input such as their hand being held, playing music through headphone, or spraying a favourite scent or perfume in the room could all beneficial.

Visitors should talk to the individual, even if there’s no sign of a response. It’s also important to be aware that any conversations which take place may be overheard and remembered, even when the individual appears to be in a deep coma.

Prognosis

The potential for recovery from a coma depends greatly on the underlying cause, but it typically only lasts for a few weeks before the individual either begins to slowly regain consciousness or else progress onto either a vegetative state, or a minimally conscious state.

A vegetative state means that the individual has “woken” from the coma and may appear to be awake but despite this continues to show no awareness of either themselves or their environment and there  are no responses to stimuli. A minimally conscious state is similar but the individual does have a limited awareness, but this is transient, and may disappear and reappear regularly.

It is possible to recover from both a vegetative state or a minimally conscious state, but some individuals remain this way for many years, and others never recover at all.

For individuals who wake from a coma, recovery is likely to be slow and arduous, not a sudden, miraculous regaining of consciousness. There may be significant confusion and agitation at the beginning.

Although a coma is a very significant event, some individuals go on to make a full recovery with any sequelae. Others suffer damage to their brain as a result of the coma and have a permanent disability. This could be of varying degrees of severity.

Requiring support from occupation therapy, physiotherapy and psychologists is part of the normal process of rehabilitation. Some individuals will require ongoing support, perhaps lifelong support, in these areas.

There are a number of factors which help to determine the possibility of making a recovery from a coma. These include:

1. Age
2. Cause
3. Extent of brain injury incurred
4. Length of time in a coma

Although these factors can be good indicators of the possibility of recovery, they should not be interpreted as definite. Knowing whether the individual will make a recovery, and the extent of that recovery is very much uncertain, despite the presence of the above positive features. Identifying the cause and treating it promptly can be a very decisive factor.

There are some exceptions as in some cases, a coma can be reversed almost straight away, such as when a blood sugar imbalance is to blame. Early intervention is key, because the longer the condition lasts, the greater the risk of permanent brain damage occurring. The same principles apply for causes such as poisoning or drugs.