Not all brain injuries involve a blow to the head or lesion. Indeed, your brain can be injured even when nothing comes into contact with your head. Anoxic brain injuries occur when the brain is deprived of oxygen. The aftermath of a lack of oxygen to the brain is largely dependent on the extent of the oxygen deprivation, also known as hypoxia. Some people recover with little to no consequences, while others need years of rehabilitative therapy.
Brain Oxygen Deprivation: The Basics
Doctors typically refer to two distinct forms of oxygen deprivation: anoxic brain injuries occur when the brain is totally deprived of oxygen due to sudden cardiac arrest, choking, strangulation, and other sudden injuries. Hypoxic brain injuries occur when the brain receives less oxygen than it needs, but is not completely deprived of oxygen. Because the effects of the two injuries are similar, many brain experts use the terms interchangeably.
A few seconds of oxygen deprivation won't cause lasting harm, so a child who holds his breath in frustration, a combatant choked unconscious during a Jiu-Jitsu, and a diver who needs a few extra seconds to come up for air are unlikely to experience brain damage. The precise timeline of anoxic brain injuries depends on a number of personal idiosyncrasies, including overall brain and cardiovascular health, as well as the level of blood oxygenation at the time of injury. Generally speaking, injuries begin at the one-minute mark, steadily worsening thereafter:
- Between 30-180 seconds of oxygen deprivation, you may lose consciousness.
- At the one-minute mark, brain cells begin dying.
- At three minutes, neurons suffer more extensive damage, and lasting brain damage becomes more likely.
- At five minutes, death becomes imminent.
- At 10 minutes, even if the brain remains alive, a coma and lasting brain damage are almost inevitable.
- At 15 minutes, survival becomes nearly impossible.
There are, of course, exceptions to every rule. Some training routines help the body make more efficient use of oxygen, enabling the brain to go longer periods without this vital element. Free divers routinely train to go long periods without oxygen, and the current record holder held his breath for 22 minutes without sustaining brain damage!
Why the Brain Needs Oxygen
The brain represents just 2% of body weight, yet it uses about 20% of the body's oxygen supply. Without it, the brain can't perform even the most basic functions. The brain relies on glucose to power neurons that control everything from conscious functions like planning and thought to automatic unconscious processes like heart rate and digestion.
Without oxygen, the brain's cells cannot metabolize glucose, and therefore cannot convert glucose into energy.
When your brain is deprived of oxygen, then, the ultimate cause of brain death is inadequate energy to power the brain's cells.
Signs of Oxygen Deprivation
Most cases of oxygen deprivation have an immediate, obvious cause. A person is at risk of oxygen deprivation under a number of circumstances, including:
- Strangulation, which blocks blood flow to the brain, thereby preventing oxygen from getting to the brain's cells.
- Cardiac or respiratory arrest due to accidents, heart attacks, strokes, and similar catastrophic events.
- Brian tumors that impede blood flow.
- Heart arrhythmias.
- Smoke or carbon monoxide inhalation.
- Extremely low blood pressure, which is common when the body goes into shock due to other injuries.
- Poisoning, including via overdose of prescription and illicit drugs or alcohol.
- Broken or compressed trachea.
- Birth-related injuries in newborns.
Early signs of oxygen deprivation include:
- Changes in heart rate.
- Decreased circulation in the hands or feet.
- Parts of the body turning blue.
- Fainting, seeing spots, or being unable to think clearly.
- Decreased judgment or awareness.
- Inability to follow directions or complete complex tasks.
Oxygen deprivation is always a medical emergency demanding prompt attention. If you suspect someone is suffering from oxygen deprivation, call 911 immediately. Rapid intervention can be life-saving, and may reduce the risk of serious, lifelong brain damage.
Effects of Oxygen Deprivation
The effects of oxygen deprivation are similar to those of other brain injuries. The prognosis depends on how severe the lack of oxygen to the brain was, the extent of neuron death, and the quality of medical and rehabilitative care. With quality physical therapy, your brain may learn to compensate for damaged regions, so even severe injuries warrant an ongoing commitment to physical therapy.
Common long-term effects of oxygen deprivation can include:
- Damage to specific brain regions deprived of oxygen. Various brain regions tend to coordinate different functions, so some functions might be severely crippled, while others remain intact. For instance, the injury survivor might be able to understand language but unable to speak.
- Changes in mood or personality.
- Difficulty with memory, including the ability to recall facts, names of objects or people, recognize faces, learn new information, or recall autobiographical facts.
- Changes in motor skills. A number of brain regions help coordinate movement, so if these areas are damaged, you may struggle to walk, write, or engage in other functions.
- Chronic pain. When the brain is damaged, it may incorrectly process pain signals, causing you to feel pain even when there is not an injury.
- The inability to feel pain, or to correctly respond to pain signals. For instance, pain in your arm might feel like pain in your leg.
- Difficulties with impulse control. Many brain injury survivors develop addictions, aggressive behavior, or sexually inappropriate compulsions.
- Symptoms of mental illnesses such as depression or anxiety.
- Dementia-like symptoms, including confusion, memory difficulties, and signs of rapid brain aging.
Treatment for Brain Oxygen Deprivation
Treatment should always begin with addressing the source of oxygen deprivation, since the longer oxygen deprivation continues, the more severe the damage will likely be. Your doctor may use a tracheotomy to ensure you get sufficient oxygen if something blocks your wind pipe. Other treatment options may include surgery to remove a blockage or lesion, and steroids to reduce swelling in your brain.
In the days following your injury, your treatment team will turn its attention toward long-term recovery. Your brain is highly adaptive to its environment, so continued challenges are the best option for helping your brain recover and work around your injuries. Your treatment plan may include:
- Exercise therapy to increase blood flow to the brain.
- Physical therapy to help you regain lost motor function.
- Occupational therapy to help you find new ways to complete everyday tasks.
- Speech therapy to help you regain lost speech and language.
- Psychotherapy to help you learn to cope with your injuries.
- Family support groups to educate you and your family about life with a brain injury.
You may also need follow-up treatments, such as chemotherapy to further shrink a brain lesion, medication to prevent a blood clot, or regular MRI scans to assess brain damage.
- Olson, Leslie C., How Brain Death Works, https://science.howstuffworks.com/life/inside-the-mind/human-brain/brain-death1.htm
- Brain Death, https://www.nhs.uk/conditions/brain-death/
- Brain Injury By a Lack of Oxygen/Oxygen Deficiency, Brain Injury Explanation, https://www.braininjury-explanation.com/causes-disorders/brain-injury-by-lack-of-oxygen
- What Happens to the Brain Without Oxygen?, AB Studio, https://youtu.be/f_R_9Z0Afcw
Written by Zawn VillinesZawn Villines is a writer specializing in health and legal journalism. Raised by a lawyer and lobbyist who advocated for spinal cord injury survivors, she is a lifelong advocate for spinal injury victims and their loved ones. You can connect with Zawn on Google+ below.
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