A loss of consciousness of a few seconds or minutes is a mild injury and rarely results in permanent brain damage. Most fighters with such injuries are not admitted to the hospital. The loss of the consciousness results from a pressure wave from the force of the blow. If the pressure of the wave is higher than the person’s blood pressure, blood flow to the brainstem is interrupted and the person passes out. As the pressure wave recedes and blood flow to the brainstem returns, the person come to. Even if the person makes a full recover, years later, at post-mortem examinations, speck-like hemorrhages, called petechial hemorrhages, may be seen in the brain. Sometimes small tears are found in the fiber tracts of the brain, called white matter, that transmit messages from one region of nerve cells, called gray matter, to another region. Although each mild injury is not serious, repeated mild injuries may have a cumulative effect and may result in permanent brain damage. As the tiny petechial hemorrhages and the tiny tears in the white matter accumulate over time, a fighter may begin to stagger, lose balance, experience short-term memory loss, and make movements as if they were still in the ring, called being punch drunk”
A loss of consciousness of 1–24 hours is a moderate head injury. Most fighters with such injuries are admitted to the hospital. Moderate head injuries may or may not result in permanent brain damage. In a moderate injury, as the pressure wave recedes, the person does not regain consciousness because of secondary complications, such as:
- Epidural Hematoma. Bleeding from a tear in an artery in the space between the skull and the outer covering of the brain (the dura).
- Subdural Hematoma. Bleeding from a tear in a vein between the dura and the brain.
- Intra-cerebral Hematoma. Bleeding into the brain itself.