Diffuse Axonal Injury

Excerpt

In the United States, traumatic brain injury (TBI) is a leading cause of death and disability among children and young adults. The Centers for Disease Control and Prevention (CDC) estimates that there are over 1.5 million reported cases of TBI every year in the United States. TBI is classified as mild, moderate, and severe based on the Glasgow coma scale (GCS). TBI patients with a GCS of 13 to 15 are classified as mild, which includes the majority of TBI patients. Patients with a GCS of 9 to 12 are considered to have a moderate TBI, while patients with a GCS below 8 are classified as having a severe TBI.

The GCS measures the following responses to 3 functions:

1. Eye opening (E)

   1. (4): spontaneous

   2. (3): to voice

   3. (2): to pain

   4. (1): none

2. Verbal response (V)

   1. (5): normal conversation

   2. (4): oriented conversation

   3. (3): words, but not coherent

   4. (2): no words, only sounds

   5. (1): none

3. Motor response (M)

   1. (6): normal

   2. (5): localized to pain

   3. (4): withdraws to pain

   4. (3): decorticate posture

   5. (2): decerebrate

   6. (1): none

Diffuse axonal injury (DAI) is a type of TBI that results from a blunt injury to the brain. DAI is caused by rapid rotational or linear acceleration-deceleration forces that stretch and disconnect white-matter tracts. Although often invisible on initial CT, DAI underlies a substantial proportion of the TBI patients and is a leading determinant of prolonged coma and long-term disability. Clinically, patients with DAI can present with a spectrum of neurological dysfunction. This can range from clinically insignificant to a comatose state. However, most patients with DAI are identified to have severe TBI.

Some authors have suggested the use of the term traumatic axonal injury instead of DAI, because the axonal injury in DAI is multifocal rather than diffuse. The NIH CDE repository defines traumatic axonal injury as the presence of "multiple, scattered, small hemorrhagic and/or nonhemorrhagic lesions in a more confined white matter distribution".