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Diffuse Axonal Injury: Grading, Treatment & Recovery

Instructor: Lisa Millraney

Lisa has 27 years of experience treating speech, language, memory and swallowing disorders. She has a master's degree in speech pathology from Vanderbilt University.

In this lesson, we will learn about the type of brain injury known as diffuse axonal injury. We will discuss its causes and treatment approaches, as well as the system of grading the injury and factors that impact the prognosis for recovery.

The Moment of Impact

It happened in an instant, during a hotly contested international auto race. Two drivers, Luis and James, were jockeying for position when something went terribly wrong. Both their cars spun wildly out of control and crashed. Racing fans watched in horror as the two were carefully removed from the wreckage of their vehicles and rushed away in ambulances.

Carla and Gino were huge racing fans and saw the accident on TV. They waited along with the rest of the world for word on the two popular drivers' conditions. Finally a statement was released: both drivers had suffered multiple injuries, but the most serious was diffuse axonal injury. ''What does that even mean?'' Gino exclaimed.

''I don't know,'' Carla replied, ''but my cousin Rebecca is a nurse. I bet she'll know.''

Diffuse Axonal Injury--What It Is

When Carla asked her cousin, Rebecca explained that diffuse axonal injury or DAI is a type of closed head injury, an injury that does not involve an open wound to the head or skull. It's a common injury, but can be quite severe. It is most frequently caused by car accidents, but can also be found in babies who have been shaken by abusive caregivers, athletes who are hit during a play, or soldiers who encounter explosives.

As the name implies, the damage to the brain is diffuse, extending over a large area. It is caused by violent movement of the brain within the skull, and results in shearing damage to the axons. They are the cells that carry messages between the grey and white matter of the brain. The axons get torn, and swelling or edema can result. Thus, the communication between parts of the brain is disrupted, and functions like speech, consciousness, and even breathing can be interrupted or cease altogether. ''Both Luis and James were probably unconscious when they were taken to the hospital,'' Rebecca said.

Diagnosing and Grading DAI

Rebecca continued by saying,''At the hospital, they were probably given an MRI, or magnetic resonance imaging test. It's the best at detecting the injuries of DAI. Other tests, like a CT scan, can't detect the tiny widespread tears and swollen spots.''

Rebecca told Carla and Gino that in severe cases of DAI, as many as 9 out of 10 patients never wake, a condition called persistent vegetative state. However, many cases of DAI are not nearly that severe. DAI is graded based on where the damage is. A Grade 1 is injury just to the axons; Grade 2 also has damage to the corpus callosum, the bundle of nerves that connect the right and left halves of the brain. Grade 3 is the worst, affecting the brainstem as well. Since that's where a lot of the basic functions of life are controlled, Grade 3 patients are the ones who generally remain in a persistent vegetative state.

Treatment of DAI--Stabilization and 'Watchful Waiting'

''It sounds awful!'' Gino said. ''So how do doctors treat it?''

Rebecca related the treatment steps: ''The first step is to stabilize the patient and keep the brain from swelling--the edema often causes as much damage as the tearing of the axons.'' She explained that there wasn't anything surgical that could usually be done to control or repair DAI, although in cases of extreme swelling, a surgeon may have to open the skull to give the brain room to expand and prevent even more damage.

Medications are most commonly used to manage the swelling. If the patient can't breathe on their own, they will need a ventilator to breathe for them. ''After those treatments are applied,'' Rebecca said, ''the medical staff's main job is what we call 'watchful waiting'. We closely monitor all the patient's vital signs, watch for brain swelling to go down, and wait for them to wake up. It can be frustrating, but it's very exciting when the patient finally regains consciousness. The sooner that happens, the better the prognosis.''

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