Explanation of Coma and Persistent Vegetative State

Author: Thomas C. Weiss
Published: 2013/12/11 - Updated: 2023/09/15
Publication Type: Informative
Topic: Traumatic Brain Injury (TBI) - Publications List

Page Content: Synopsis - Introduction - Main

Synopsis: Information regarding coma, a lengthy deep state of unconsciousness and vegetative state where a person can be awake yet is entirely unaware. Unlike a person in a coma, a person in a PVS has sleep and wake cycles or periods when they are awake and asleep.

Defining Coma

Coma: A coma is a lengthy deep state of unconsciousness. People in a coma are alive but cannot move, be aware of, or respond to their surroundings. They lose their thinking abilities but retain non-cognitive functions and standard sleep patterns. Comas can be derived from natural causes or can be medically induced. A coma can have various reasons, including traumatic head injury, stroke, brain tumor, or drug or alcohol intoxication. An underlying illness, such as diabetes or an infection, may cause a coma. A coma rarely lasts beyond two to four weeks. However, some people with coma enter a deeper unresponsiveness or a persistent vegetative state that may remain for years or even decades. Some people may face "brain death," where there is no brain activity, and critical functions like independent breathing are shut down. Removing assistive equipment at this point will lead to death.

Introduction

Coma is a state in which a person's cortex, or higher brain areas, are damaged, resulting in loss of consciousness, an inability to be roused, and unresponsiveness to sound, pain, light, and touch. If the person's lower brain centers are damaged, a respirator might be needed for them to breathe. The damage may be reversible or irreversible. There are various causes of coma, including:

Hypothermia
A post-seizure state
Trauma to the brain
Masses or tumors in the brain
Toxic effects of alcohol or drugs
Stroke caused by clots or bleeding
A lack of oxygen to the brain for prolonged periods

A person may also experience metabolic imbalances such as low or high blood sugar, high blood calcium, or kidney or liver failure abnormalities.

Main Item

Persistent Vegetative State (PVS)

A vegetative state exists when a person can be awake yet is completely unaware. A person in a vegetative state can no longer think, reason, or relate meaningfully with their environment, recognize the presence of those they love, or feel emotions or discomfort. The higher levels of their brain no longer function. A vegetative state is called 'persistent' if it lasts longer than four weeks. As with a person who is in a coma, a person who is in a PVS is completely dependent on all care needs, cannot drink or eat, cannot speak, and is incontinent.

Unlike a person in a coma, a person in a PVS has sleep and wake cycles, or periods when they are awake and asleep. The person can sometimes sneeze, cough, and even smile or cry. The person might, at times, move their legs or arms. A person in a PVS may react automatically to touch, such as drawing a body part away, to sound - such as turning their head toward the sound, or light, such as blinking their eyelids. The person's eyes might move randomly.

If the person's gaze happens to momentarily stop in the direction of someone at the side of their bed, the person might misinterpret the gaze as the person in the PVS is looking at them. The behavior may be confusing and disconcerting to the onlooker, particularly a loved one, who might interpret the gaze as indicating that the person in a PVS is aware but unable to communicate with those around them. All of the behaviors described are automatic and do not require any functioning of the thinking portion of the person in a PVS brain.

Causes of a PVS

Coma has the potential to progress to a PVS. A person rarely remains in a coma for more than 2-4 weeks without recovering, dying, or progressing to a PVS. End-stage dementia may also progress to a PVS.

The rate of recovery is greatly dependent on the cause of the coma or PVS, whether the cause is reversible or not, the amount of damage to the person's brain, the region of the person's brain that is damaged, and the amount of time the person is in a coma or a PVS. When the cause of a coma is corrected before permanent brain damage happens, the coma usually reverses within days.

Unfortunately, when the death of large areas of a person's brain happens, the outcome is often grim. Dead brain tissue does not regenerate. Recovery from illnesses symptomatic of dead brain tissue, such as a stroke, usually is a result of other brain tissue being trained to assume the functions of the tissue that has been lost. If there is not enough brain tissue left to take over the functions of the lost brain tissue, the person will not recover.

The longer a person is in a coma, the larger and more diffuse the area of damage. The older the person, the less their chances are for experiencing a reversal of the coma and recovery of function. Since PVS is a late-stage outcome of causes of irreversible coma or the end stages of dementia, the outlook for a person's recovery is always poor for a person in this condition.

Recovery from a Coma after Months or Years

People who recover from a coma after months or even years are scarce. Suppose a coma is caused by traumatic injury with bleeding in the person's brain, and the injury is limited. In that case, the person can recover - even when the coma has lasted for several months. The chances are greater in younger people. Yet even in a young person who has experienced brain trauma, if the coma lasts longer than six months, the person rarely recovers.

If someone experiences a prolonged coma, not due to trauma such as one due to a stroke, the chance of recovery is small. The rare person destined to recover will show some increase in responsiveness and functioning, no matter how gradual, within the first days to weeks of becoming unconscious. The lack of any improvement over some time is a signal they will not recover.

A person who experiences a prolonged coma due to irreversible damage to their brain caused by a prolonged period of oxygen deprivation has the least chance of recovering. If a coma from this condition, known as 'anoxic encephalopathy,' lasts longer than a week - recovery is sporadic. If the person does not die, they usually progress to a PVS.

Physical Impact of Prolonged Coma or PVS

The notion that an irreversible coma or PVS is a stable and non-progressive condition is inaccurate. While the brain lesion might not be changing or expanding, the changes happening to a person's body are progressive. The physical results of prolonged coma or PVS include the following:

The belief that an irreversible coma or a PVS is a stable non-progressive condition is inaccurate. Although the brain lesion may not be changing or expanding, the changes occurring in the body are relentlessly progressive:

Risk of sepsis
Muscle wasting
Limb contraction
Risk of pneumonia
Skin breakdown/ulcers
Risk of lung scarring or collapse
Recurrent urinary tract infections

The longer a person is in a coma or PVS, the more profound and devastating the physical changes they experience. There are several characteristics of a vegetative state as well. These characteristics include:

No purposeful movement
Inability to follow instructions
Inability to speak or communicate
Might moan or make other sounds
May react to a loud sound with a startle
May smile or cry or make facial expressions
Might briefly move eyes toward people or objects
Sleep-wake cycle with periods of eye-opening/closing

At times, what is referred to as a 'secondary injury' can make being in a coma or vegetative state even direr. Secondary injuries may include pneumonia, infections, or bedsores. People emerging from a coma might also be threatened by a lack of appropriate nutrition, contractures, and deformities of their joints, bones, and muscles.

There are no exact numbers concerning how many people emerge from a coma or how many people will die while in a coma. Research has shown that most people emerge from deep comas within weeks after experiencing a brain injury. Each person, as well as the brain injury they experience, is unique. At times even doctors are surprised by a person's recovery. Instead of emphasizing complete recovery, treatment pursues improved function, prevention of further injury, and rehabilitation of people and their family members on physical and emotional levels.

Author Credentials: Thomas C. Weiss is a researcher and editor for Disabled World. Thomas attended college and university courses earning a Masters, Bachelors and two Associate degrees, as well as pursing Disability Studies. As a CNA Thomas has providing care for people with all forms of disabilities. Explore Thomas' complete biography for comprehensive insights into his background, expertise, and accomplishments.