Surgical Craniotomy for Trauma

^K diffuse axonal injury (DAI), the most severe of all brain injuries, occurs when nerve axons are stretched, sheared, or even torn apart. The severity and outcome of a DAI depend on the extent and degree of damage to brain structures and can be classified as mild, moderate, or severe DAI. All types of DAI are associated with an immediate and prolonged (>6 hours) coma. Mild DAI is associated with a coma that lasts from 6 to 24 hours and has a 15% mortality rate; 80% of patients experience a good recovery. Moderate DAI, the most common form, is associated with a coma that lasts 24 hours or more, decerebration (extension posturing), and decorti-cation (flexion posturing). Approximately 25% of patients with moderate DAI die. Severe DAI, which has a mortality rate of 50%, occurs when there is an extensive disruption of axons in the white matter of the central nervous system (CNS). People who emerge from coma usually do so in the first 3 months after injury, but many of those who live remain in a persistent vegetative state.

The pathophysiology of DAI is based on a model of shear injury; the brain trauma occurs because of sudden acceleration-deceleration impact can produce rotational forces that affect the brain. The injury to tissue is greatest in areas where the density difference in the brain is greatest, so most of DAI lesions occur at the junction of gray and white matter. Injury results in edema and axonal tearing, and the severity of injury depends on the distance from the center of rotation, the arc of rotation, and the duration and intensity of the force.

0 0

Post a comment