Traumatic brain injury classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Traumatic brain injury may be classified into several subtypes including focal or diffuse, open or close, and mild, moderate or severe.

Classification

• Focal vs. Diffuse
  • The damage from TBI can be focal, confined to one area of the brain, or diffuse, involving more than one area.
  • Diffuse trauma to the brain is frequently associated with concussion (a shaking of the brain in response to sudden motion of the head), diffuse axonal injury, or coma.
  • Localized injuries may be associated with neurobehavioral manifestations, hemiparesis or other focal neurologic deficits.
  • Types of focal brain injury include bruising of brain tissue called a contusion and intracranial hemorrhage or hematoma, heavy bleeding in the skull.
  • Hemorrhage, due to rupture of a blood vessel in the head, can be extra-axial, meaning it occurs within the skull but outside of the brain, or intra-axial, occurring within the brain.
  • Extra-axial hemorrhages can be further divided into subdural hematoma, epidural hematoma, and subarachnoid hemorrhage.
  • An epidural hematoma involves bleeding into the area between the skull and the dura.
  • With a subdural hematoma, bleeding is confined to the area between the dura and the arachnoid membrane.
  • A subarachnoid hemorrhage involves bleeding into the space between the surface of the brain and the arachnoid membrane that lies just above the surface of the brain, usually resulting from a tear in a blood vessel on the surface of the brain.
  • Bleeding within the brain itself is called an intracerebral hematoma.
  • Intra-axial bleeds are further divided into intraparenchymal hemorrhage which occurs within the brain tissue itself and intraventricular hemorrhage which occurs into the ventricular system.

• Open vs. Closed
  • TBI can result from a closed or penetrating head injury.
  • A closed injury occurs when the skull is not breached, while a penetrating injury occurs when an object pierces the skull and enters brain tissue.
  • As the first line of defense, the skull is particularly vulnerable to injury.
  • Skull fractures occur when a bone in the skull cracks or breaks.
  • A depressed skull fracture occurs when pieces of the broken skull press into the tissue of the brain.
  • A penetrating skull fracture occurs when something pierces the skull, such as a bullet, leaving a distinct and localized traumatic injury to brain tissue.
  • Skull fractures can cause cerebral contusion.

• Severity
  • Head injuries can be subdivided into mild, moderate, and severe TBI to help predict outcome.
  • One common classification system determines severity based on the Glasgow Coma Scale (GCS) and duration of post-traumatic amnesia (PTA) and loss of consciousness (LOC) according to the table at right.
  • Other classification systems use GCS alone or PTA or LOC alone or together.
  • Prognosis worsens with the severity of injury, but mild TBI is more poorly defined and prognosis is not as clear with it.
  • Mild TBI is also commonly called concussion.
  • Though prognosis for concussion is usually very good, a portion of people may suffer lasting problems associated with the injury, such as post-concussion syndrome.
  • A patient who receives a second concussion before symptoms from another one have healed is at risk for developing a very rare but deadly condition called second-impact syndrome, in which the brain swells catastrophically after even a mild blow.

Levels of TBI severity

	GCS	PTA	LOC
Mild	13 to 15	<1 hour	<30 minutes
Moderate	9 to 12	30 minutes to 24 hours	1 to 24 hours
Severe	<8	>1 day	>24 hours