Diffuse axonal injury (DAI) is a type of traumatic brain injury (TBI). It refers to the shearing of the brain’s long connecting nerve fibers, or axons. DAI can occur during a motor vehicle accident and can lead to a coma.
DAI, also known as traumatic axonal injury, occurs when a sudden violent blow or jolt to the head causes damage to the brain. After the impact, the brain may collide with the inside of the skull, which can result in the shearing of nerve fibers. The injury happens when the brain shifts and rotates inside the skull.
This can affect the ability of various brain regions to communicate with other areas, which may lead to neurological problems, as well as coma, long-term impairment, or death.
In this article, we discuss diffuse axonal injury in more detail, including its causes, how doctors grade it, and the outlook for people with this condition.
Traumatic axonal injury or
Specifically, DAI describes the shearing, or tearing, of nerve fibers known as axons. This trauma usually results from the brain quickly shifting within the skull. Following a sudden impact, mechanical forces cause nerve fibers to stretch and tear.
Axons are the long, thread-like portion of neurons that conduct electrical impulses. They are responsible for communication between nerve cells. As such, damage to axons may impair their ability to communicate and help coordinate bodily functions, which can lead to severe disabilities.
DAI is the most common cause of coma, disability, and persistent vegetative state in people with TBI. Clinically, health experts define DAI as a loss of consciousness that lasts for 6 hours or more after the injury. It may also cause behavioral, social, physical, and cognitive changes in a person that may be temporary or permanent.
DAI is more common in high energy traumatic accidents in which the brain rotates or moves forward or backward inside the skull. Typically, this type of trauma involves accelerating and decelerating motions. If these forces are sufficiently strong, they can damage axons, causing these neuronal interconnections to malfunction or disconnect and affecting many brain areas. DAI commonly affects the
- frontal lobe white matter
- temporal lobe white matter
- corpus callosum
- brain stem
The leading causes of DAI include:
- motor vehicle accidents
- sports-related accidents
- accidental falls, which are more common among older adults
- shaken baby syndrome
Following the traumatic impact, a person with DAI typically presents with loss of consciousness and poor neurological examination results. Experts use the
They calculate a value by adding the totals from three different categories to get a score that ranges from a minimum of 3 to a maximum of 15. A lower score indicates a higher level of impairment. A person with DAI will typically have a GCS score of
- Spontaneous: 4
- In response to speech: 3
- In response to pain: 2
- None: 1
- Orientated response: 5
- Confused conversation: 4
- Inappropriate response: 3
- Incomprehensible sounds: 2
- None: 1
- Obeying commands: 6
- Movement localized to stimulus: 5
- Withdraws: 4
- Abnormal muscle bending and flexing: 3
- Involuntary muscle straightening and extending: 2
- None: 1
The clinical presentation of DAI depends on the severity of the brain injury. In mild cases of DAI, a person may have symptoms that mimic concussion symptoms, including:
Those with more severe DAI may present with loss of consciousness and stay in a vegetative state. Other neurological manifestations of DAI can include dysautonomia. This term describes when the autonomic nervous system does not work as it should. The symptoms may include:
DAI is a
The results of imaging tests can also help doctors make a diagnosis. These tests may include a brain MRI or diffuse tensor imaging (DTI). A
Doctors may also use the
- Grade 1, or mild DAI: Microscopic damage to the white matter of the brain, including changes in the cerebral cortex, brain stem, and corpus callosum.
- Grade 2, or moderate DAI: Larger lesions present in the corpus callosum.
- Grade 3, or severe DAI: Larger lesions present in both the brain stem and the corpus callosum.
The treatment of DAI is similar to the treatment of other head injuries. The goal of emergency care is to
- ensuring that the airway is open
- providing ventilation and oxygen
- maintaining blood pressure
After emergency care, a person may need medications and surgery to help control the symptoms. They may also require rehabilitation. Depending on the extent of the injury, they may need to relearn many everyday tasks, such as how to walk and talk.
Health experts generally
A very small number of those with severe DAI regain their consciousness within the first year after the injury. If a person regains their consciousness and becomes stable, a comprehensive therapeutic program from their brain injury rehabilitation team can help restore their quality of life. This program may include:
- wearing a seatbelt whenever riding in or driving a vehicle
- avoiding driving when under the influence of drugs or alcohol
- wearing the appropriate protective gear or helmet for the sport or activity
- evaluating an older adult’s risk of falling and taking steps to reduce their risk
- keeping the home safe and clutter-free
Diffuse axonal injury describes a severe type of traumatic brain injury. It refers to when trauma causes the brain to shift in the skull, resulting in the shearing of axons. This injury is often fatal. In other cases, a person may remain in a vegetative state or have permanent disability.
Immediate emergency treatment is necessary to stabilize an individual after the injury. Although the outlook for these individuals is usually not positive, a comprehensive therapeutic program can help restore quality of life. To prevent DAI, it is advisable for a person to take suitable safety precautions, such as wearing a seatbelt when traveling in a vehicle.