A diffuse axonal injury (DAI) is a type of brain injury which involves damages to the axons, caused by shearing forces which push tissues in the brain past each other. As the “diffuse” in the name implies, a diffuse axonal injury can cover a large area of the brain, as opposed to a focal injury, in which the damage is concentrated in one region. These injuries can be challenging to diagnose because the damage may not always show up in medical imaging studies.
Diffuse axonal injuries are classically caused by things like car accidents, falls, and abuse. Anything which shakes, rapidly rotates, or abruptly decelerates the head can lead to a diffuse axonal injury, because it puts shearing stresses on the brain. The hallmark symptom of this type of injury is unconsciousness. In around 90% of patients, the patient actually never regains consciousness after a DAI, and for the 10% who wake up, recovery can be a long process.
This type of brain injury is extremely common, and it's among the most fatal types of brain injury. On the mild end of the spectrum, a diffuse axonal injury can cause a concussion. More commonly, people become severely impaired. Individuals who regain consciousness generally need a great deal of supportive care, and improvements in their condition are usually seen within the first year, although therapy and treatment should still be continued after this point.
Immediate treatment for a diffuse axonal injury involves supporting the patient while she or he is unconscious. Pressure inside the skull is monitored carefully so that it can be relieved if it gets too high, and the patient may be placed on a ventilator if breathing difficulties arise. For patients who do not regain consciousness, lifetime support in a treatment facility for people with traumatic brain injuries is needed. For patients who wake up, recovery can include physical therapy, speech therapy, occupational therapy, and other support measurements to help the patient regain as much function as possible.
The prognosis for someone with a diffuse axonal injury varies. Some people recover very well, and may experience no long term effects. Other people may require supportive therapy throughout their lives, but be quite independent otherwise, and some develop severe impairments which require them to have aides at all times. Patients who do not regain consciousness are unlikely to improve, and the costs for their care can be extremely high.