Which type of traumatic brain injury is caused by an external force contacting the head, suddenly placing the head in motion?

• A. Deceleration injury
• B. Acceleration injury
• C. Coup injury
• D. Contrecoup injury

Answer: (B)

External force causing rapid acceleration of the head drives the brain to move differently from the skull due to its inertia. When the head is suddenly struck, the skull accelerates quickly while the brain tends to stay in place, creating shear and stretch within neural tissue. This pattern defines an acceleration injury and often leads to diffuse injury mechanisms.

In contrast, deceleration injury comes from the head continuing to move after the initial impact and then slowing down, which produces a different set of forces. Coup injury refers to damage at the site of impact on the brain surface beneath the skull, while contrecoup injury is damage on the opposite side, from the brain rebounding and striking the skull after the initial impact.