What is Diffuse Axonal Injury & How is it Treated?
What is a Diffuse Axonal Injury?
Diffuse Axonal Injury (DAI) is a one of the most fatal and common brain injuries. Severe diffuse axonal injury is one of the major causes of death in patients suffering from traumatic brain injury. In Diffuse Axonal Injury, patient has extensive damage where there is formation of widespread lesions in the white matter tracts over a widespread region. Diffuse axonal injury is the leading cause of unconsciousness and constant vegetative state after serious head injury. Diffuse axonal injury is seen in about 50% of patients who have suffered severe head injury. The prognosis of diffuse axonal injury is not good as it often results in patient being in a coma, where more than 90% of them with severe diffuse axonal injury do not regain consciousness and those who do, mostly become significantly impaired.
There are different degrees of severity of diffuse axonal injury. It can be mild to moderate to severe. Concussion is thought to be a milder form of diffuse axonal injury.
Classification of Diffuse Axonal Injury (DAI)
Diffuse axonal injury comes under the heading of a diffuse brain injury, which means that it is not restricted to a specific area and occurs in a widespread area. Based on the severity of the injury, diffuse axonal injury is classified into:
Grade-I Diffuse Axonal Injury: There is widespread axonal damage without any focal abnormalities.
Grade-II Diffuse Axonal Injury: Along with widespread axonal damage, focal abnormalities are also present, particularly in the corpus callosum.
Grade-III Diffuse Axonal Injury: There is widespread axonal damage, focal abnormalities along with injury to the rostral brainstem which often results in tears in the tissue.
Causes of Diffuse Axonal Injury (DAI)
The cause of diffuse axonal injury is not a simple blow to the head, but a severe cutting force to the head, which results in rapid acceleration or deceleration; or backwards and forwards movement of the brain, within the skull. Some of the causes where this type of head injury leading to diffuse axonal injury includes: An automobile accident, physical violence/abuse, sports injuries, falls and shaken baby syndrome, which is child abuse.
Violent and rapid acceleration or deceleration of the brain leads to its displacement within the skull resulting in disruption of axons, which are responsible for sending messages between neurons; and are also parts of nerve cells. Patient has shearing injury to the brain where there is sliding of tissue over tissue resulting in development of lesions, which are responsible for unconsciousness and the vegetative state occurring after a traumatic brain injury. Death of brain cells also occurs from a diffuse axonal injury resulting in swelling in the brain. This in turn leads to increased pressure within the brain causing diminished blood circulation to the brain adding further brain injury. The shearing force also discharges chemicals which further damages the brain.
Symptoms of Diffuse Axonal Injury (DAI)
Loss of consciousness is the primary symptom of diffuse axonal injury. This can persist up to 7 hours or more. Depending on the region of the brain that is most affected, patients suffering from mild to moderate diffuse axonal injury, and who are conscious, can exhibit other signs of brain damage. It is imperative to seek immediate medical treatment if someone suffers from such symptoms.
Diagnosis of Diffuse Axonal Injury (DAI)
If the patient is conscious and has sustained mild diffuse axonal injury, then patient’s medical history will be asked along with other questions, such as the method of the injury and the type of symptoms experienced by the patient. Patient’s cognitive function is also tested along with other tests to determine the degree of the axonal injury. As majority of the patients suffering from severe diffuse axonal injury do not regain consciousness, certain imaging tests are done to assess the extent of injury and these tests are:
CT Scan: An x-ray machine along with a computer monitor is used where detailed images of the structures inside the brain can be viewed. The results of CT scan can be false negative, so this test is not always dependable in case of diffuse axonal injury.
Magnetic Resonance Imaging (MRI): In this test, radio waves and magnets with a computer screen are used, so that detailed cross-section images of the brain can be seen. This is the most preferred imaging test for diagnosis of diffuse axonal injury.
Electroencephalogram (EEG): The electrical activity in the brain is measured with the help of this test.
Diffusion Tensor Imaging: This is one of the newer tests that help in finding out the degree of injury to the white matter fiber tract even if the result of a standard MRI is negative.
Evoked Potentials: Also known as Somato-Sensory Evoked Potential (SSEP) test, Visual Evoked Potential (VEP) test, Brainstem Auditory Evoked Response (BAER) test; these are the tests which look at the auditory, visual and sensory pathways of the brain.
Treatment for Diffuse Axonal Injury (DAI)
There is no specific treatment for Diffuse Axonal Injury and treatment comprises of standard treatment to any head injury which consists of trying to halt the increase in the intracranial pressure and stabilize the patient.
Immediate steps are taken to bring down the swelling within the brain, as it causes further damage. Medications, such as steroids are given to bring down the swelling and inflammation associated with diffuse axonal injury after which the patient will be put under observation. For patient with diffuse axonal injury, surgery is not an option. Patients who have suffered mild or moderate diffuse axonal injury will undergo rehabilitation after they have regained consciousness and have stabilized. For this, patient needs attention from a multidisciplinary staff which consists of nurses, doctors, physical and occupational therapists along with other specialists who have to design an individualized recovery program for traumatic brain injury that will facilitate the patient to perform the maximum level of his/her daily function. The stage of rehabilitation for patients with Diffuse Axonal Injury includes: Physical therapy, speech therapy, occupational therapy, adaptive equipment training, recreational therapy and counseling.
Prognosis of Diffuse Axonal Injury (DAI)
The prognosis of Diffuse Axonal Injury is usually not good. Recovery is possible in mild to moderate types of diffuse axonal injury, where the patient can end up with some long-term problems. There are different degrees of severity for diffuse axonal injury where concussion is considered one of the milder forms of it.
Around 90% of patients who survive Diffuse Axonal Injury do not regain consciousness and remain in a vegetative state; whereas, the remaining 10% who regain consciousness are usually left with some type of severe impairment.