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Axonal Brain Injury

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Axonal Brain Injury

An anoxic brain injury results from a total lack of oxygen to the brain. A hypoxic brain injury results from a partial disruption of oxygen. In actuality, these injuries are on a continuum and are referred to often as  hypoxic-anoxic injuries or HAI. The longer the deprivation of blood oxygen, the more severe is the damage to the brain.Causes of Anoxic Brain InjuriesWhen the oxygen level is too low for five minutes or longer, certain brain cells begin to irrevocably die.  An anoxic brain injury is a life-threatening one and one that can lead to cognition difficulties and other disabilities.  Anoxic brain injuries mean that the brain has had virtually no oxygen for a period of time.  This is more serious than a hypoxic brain injury.  When brain cells die, this means that the performance of the neurotransmitters fails.  This explains why some of the mood and behavioral changes occur after an anoxic injury.There are Four Types of Anoxia:
  • Anemic anoxia.  This happens when the blood cannot carry enough oxygen to the brain.  This happens with certain forms of lung disease, chronic anemia, carbon monoxide poisoning and acute hemorrhage.  The blood might be there but it is not oxygenated.
  • Toxic anoxia.  This happens when toxins in the system prevent the oxygen from the blood to be used efficiently.  An example of this is carbon monoxide poisoning.
  • Stagnant anoxia. This is also referred to as hypoxicischemia. In this case, there is an internal condition that blocks oxygen in the blood from getting to the brain.  This happens in cardiac arrhythmias, strokes and cardiac arrest.
  • Anoxic anoxia.  This is a condition that happens when there is not enough oxygen in the air to sustain the body.   High altitudes can cause this as well as being a firefighter.
Common Causes of Anoxia are Electrical shock, respiratory arrest, heart attack, drowning, brain tumors, very low blood pressures, poisoning, carbon monoxide exposure, choking, respiratory conditions, certain narcotics and suffocation.
Symptoms of Anoxic Brain InjuryAn anoxic brain injury usually begins with a total loss of consciousness or coma but this doesn’t have to happen that way.  The person can also lapse into a persistent vegetative state in which they have normal sleep wake cycles but they do not respond to stimulation.  This state is also called “wakeful unresponsiveness”.  If the person awakens from their unconscious state, they may experience similar symptoms to suffering from a severe head trauma.  It all depends on the amount of tissue damage that went on during the anoxic episode.

There are many cognitive problems associated with anoxia.  There can be short-term memory loss, especially with a hypoxicischemic injury.   New information cannot be remembered because of damage to the hippocampus.  There is a worsening performance in the executive functions of reasoning, judgment and information processing.  The person can be more impulsive or indecisive.  Concentration may be lacking. The person may have anomia, which is difficulty using or processing words.  There may be visual problems, such as being unable to focus on an object one has reached for.  There may be cortical blindness, in which the eyes are normal but the person cannot see.

There can be physical problems with anoxia.  There can be a lack of coordination, called ataxia.  There may be an inability to do common tasks, such as brushing one’s teeth.  There can be movement disorders such as muscle spasticity, myoclonus and rigidity.  There can be weakness in one or more limbs and headaches.  The anoxic person can have depression, confusion, delusions, hallucinations and personality changes from their anoxic event.
Diagnosis and Treatment of Anoxic Brain InjuriesThis is a serious medical illness and treatment must occur promptly.  The medical tests that can help diagnose anoxic brain damage include the MRI scan, which is considered the gold standard for diagnosing this disease.  A CT scan, which uses computers and x-rays to create a 3 dimensional image of the brain, can also be used.  A test of the evoked potentials of the visual, sensory and auditory aspects of the brain can tell you what’s going on in terms of function.  The EEG can measure the brain’s electrical activity.  Blood tests such as arterial blood gases can tell how much oxygen is in the blood.

The trick to treating anoxic injuries is to pinpoint the cause of the problem.  If it is due to a stroke for example, the doctor needs to immediately thin the blood in order to restore blood flow to the brain.  If it is due to a heart arrhythmia, this means that the priority is to treat the arrhythmia so oxygen can get to the brain.  The idea is to restore oxygen to the brain as quickly as possible.  This will diminish brain damage to the maximal amount.

Steroids can be used to reduce brain swelling because the swelling can cause problems in and of itself.  Barbiturates can be used to reduce brain activity so the tissue has time to recover.  Anti-seizure medication is important because anoxic patients often have seizures.  Patients can be put into a drug induced coma to help them heal.  The patient still could end up with brain death even after the drug induced coma.  The longer the coma, the greater is the chance of brain death.
Once the acute phase is over, the patient enters the rehabilitation phase.  There will be a number of nurses, doctors and rehabilitation specialists involved in the patient’s recovery as the muscles will atrophy for as long as they have been in the coma.