Explanation of Coma and Persistent Vegetative State
Synopsis: Information regarding coma and vegetative state when a person has the ability to be awake yet is completely unaware of their surroundings.1
Author: Disabled World
Main DigestComa is a state in which a person's cortex, or higher brain areas, are damages resulting in loss of consciousness, an inability to be roused, as well as 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 to include:
- 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 of time
A person may also experience metabolic imbalances such as low or high blood sugar, high blood calcium, or abnormalities related to kidney or liver failure.
Persistent Vegetative State (PVS)
A vegetative state exists when a person has the ability to be awake, yet is completely unaware. A person in a vegetative state no longer has the ability to think, reason, or relate meaningfully with their environment, to recognize the presence of those they love, or to feel emotions or discomfort. The higher levels of their brain no long function. A vegetative state is referred to as, 'persistent,' if it last for longer than 4 weeks. As with a person who is in a coma, a person who is in a PVS is completely dependent for all care needs, does not have the ability to drink or eat, cannot speak, and is incontinent.
Chart showing causes of coma
Unlike a person in a coma, a person in a PVS has sleep and wake cycles, or periods when they are awake, as well as periods when they are asleep. The person can sneeze, cough, and even smile or cry at times. The person might at times move their legs or arms. A person in a PVS may have automatic reactions 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 just happens to momentarily stop in the direction of someone who is at the side of their bed, the person might misinterpret the gaze as the person in the PVS as looking at them. The behavior may be confusing and disconcerting to the onlooker, particularly a loved one, who might interpret the gaze as an indication that the person in a PVS is aware but unable to communicate to 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 times 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 a 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 extremely rare. If a coma is caused by traumatic injury with bleeding in the person's brain, and the injury is limited, the person has a chance of recovering - even when the coma has lasted for a number of months. The chances are greater in people who are younger. Yet even in a young person who has experienced a brain trauma, if the coma lasts for longer than 6 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 who is 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 a period of 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 achieving a recovery. If a coma from this condition known as, 'anoxic encephalopathy,' lasts longer than a week - recover is very rare. 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 not accurate. While the brain lesion might not be changing or expanding, the changes happening to a person's body are indeed progressive. The physical results of prolonged coma or PVS include the following:
Chart showing some of the physical impact of coma/PVS
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 a number of 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 more dire. 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 the overwhelming majority of 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, as well as rehabilitation of people and their family members on physical and emotional levels.
- 1: Videos Inspire Veterans and Service Members with TBI to Seek Help : Defense and Veterans Brain Injury Center (2016/01/05)
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- 3: Brain's Ability to Heal Itself Research Offers Hope for TBI : Henry Ford Health System (2015/03/23)
- 4: Cell Pores Discovery: Hope for Millions of Brain and Spinal Cord Injury Patients : Aston University (2020/05/17)
- 5: Canadian Government National Guidelines for Concussion Management : Public Health Agency of Canada (2016/10/30)
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<b>Journal:</b> <i>Disabled World</i>. Language: English. Author: Disabled World. Electronic Publication Date: 2013-12-11. Last Revised Date: 2013-12-11. Reference Title: <i>Explanation of Coma and Persistent Vegetative State</i>, Source: <a href=https://www.disabled-world.com/health/neurology/tbi/coma.php>Explanation of Coma and Persistent Vegetative State</a>. Abstract: Information regarding coma and vegetative state when a person has the ability to be awake yet is completely unaware of their surroundings. Retrieved 2021-02-25, from https://www.disabled-world.com/health/neurology/tbi/coma.php - Reference Category Number: DW#267-9982.