Secondary brain injuries are the injuries that cause most TBI side effects.
But what exactly are secondary brain injuries, and are there any ways to prevent them?
In today’s article, we’ll be getting a little more technical than we normally do here to give you everything you need to know about secondary brain injuries.
We’ll start by discussing the physiological processes behind secondary brain injuries, then we’ll look at the different types of secondary injuries and what measures you can take to prevent them.
Secondary Brain Injuries
Most doctors divide traumatic brain injury into two stages: primary and secondary injuries.
The primary injury refers to the direct results of initial impact or damage. For example, a blunt force can shake the brain inside the skull, which damages cerebral blood vessels and stretches the neural axons.
On the other hand, secondary injuries are the indirect results of brain injury that occur in the hours or days following an injury.
Secondary injuries almost always ultimately lead to a lack of oxygen in the brain, called cerebral hypoxia.
This lack of oxygen damages and sometimes kills brain cells previously unharmed in the initial injury, which explains why most TBI patients continue to deteriorate days after the initial blow to their head.
What Causes Secondary Brain Injuries?
The causes of secondary brain injuries are either intracranial or extracranial.
Harmful processes inside the brain, which take place immediately after primary injury, trigger intracranial secondary injuries. Extracranial injuries are caused by outside influences.
We’ll discuss the different intracranial secondary injuries first.
Intracranial Secondary Brain Injuries
Intracranial secondary injuries are the result of a cascade of harmful processes in the brain.
There are two primary sources of intracranial secondary injuries: Chemical changes and hematomas.
In the moment immediately after the primary injury, cerebral blood flow decreases, and the brain releases chemicals called free radicals, unstable oxygen molecules that inflame brain tissue.
The inflammation causes brain tissue to swell, which leads to increased intracranial pressure. (ICP)
This ICP leads to a further decrease in cerebral blood flow, which eventually causes cerebral hypoxia to set in.
As a result, nerve cells start dying.
If the skull is fractured, this usually causes a rupture in the meningeal blood vessels.
Meningeal vessels refers to arteries found on the outer portion of the protective layer of membrane (called the dura) that lies between the brain and the skull.
The blood from these broken vessels pools into a hematoma that forms in the space between the skull and the dura.
As the hematoma grows, it presses down on the brain and reduces blood flow to that area.
As a result, oxygen is restricted in those parts of the brain, and brain cells die.
Other types of hematomas, such as subdural and subarachnoid hematomas, can also form within the brain itself.
Extracranial Secondary Brain Injuries
Besides internal problems, external factors can also cause secondary brain injuries.
These factors include respiratory failure, blood loss, infections and seizures.
Respiratory failure or any sort of impairment to breathing can aggravate the brain and cause an increase in intracranial pressure, which cuts off oxygen to the brain.
Sometimes a head injury itself can disrupt a person’s ability to breathe (also known as central apnea). Or the person might aspirate on their vomit, which injures their lungs and cuts off oxygen.
This is why one of the main concerns of emergency traumatic brain injury treatment is to ensure that the person is getting enough oxygen.
Blood loss from other injuries, if left untreated, can also damage the brain.
Too much blood loss leads to anemia, which causes your brain not to receive oxygen from healthy red blood cells.
Infections and Seizures
An open head injury often leads to infection.
If the brain gets infected, this could have a devastating effect and cause even more brain damage.
Infections in the brain can also lead to seizures and epilepsy after TBI.
Seizures, left uncontrolled, will cut off blood and oxygen supply to the brain, which will only lead to more secondary brain injuries.
Preventing Secondary Brain Injuries
Preventing secondary brain injuries is crucial to keep a brain injury from worsening.
Doctors take many measures to try to reduce the harm from secondary brain injuries. These include:
- Operations to remove hematomas and relieve intracranial pressure
- Antibiotics to prevent infection
- Sedation to prevent further inflammation
Therefore, the best thing you can do to prevent secondary brain injuries, even if you think your head injury is relative mild, is to have a doctor monitor you for signs of secondary brain injury, such as hematomas or raised intracranial pressure.
The earlier the doctors can catch these secondary injuries, the better your chances of making a full recovery.