Concussion is a temporary disturbance of brain function caused by a sudden blow to the head. A concussion typically results in a temporary loss of consciousness, followed by a memory loss for the events just before and after the injury. More extensive memory loss occurs if the injury is severe. A mild concussion may or may not involve unconsciousness and memory loss. It causes a momentary state of confusion.
In a concussion, the blow causes the brain to bounce against the inside of the skull, injuring the brain’s outer surface. Injury to the inner parts of the brain may also occur. The reason unconsciousness occurs is not well understood. One theory is that the blow disturbs function of the cerebral cortex (outermost part of the brain). Another is that the blow injures the deeper parts of the brain that control sleep cycles and alertness.
Determining if an individual has suffered a concussion is often difficult because symptoms are not consistent and may not be immediately apparent. Medical professionals diagnose concussion by performing a neurological examination. This involves checking vision, hearing, balance and coordination, muscle strength, and evaluating alertness and memory. Brain imaging, such as computed tomography (CT) scans or magnetic resonance imaging (MRI), may be used for people who experience severe symptoms or symptoms that become worse over time. In 2018, the United States Food and Drug Administration (FDA) approved a blood test to diagnose concussion. The blood test can be administered within 15 minutes of a head injury and provides results within hours.
The victim of a concussion may stop breathing for a few seconds after the blow. In addition, the victim’s pulse slows, the muscles relax, the pupils widen, and certain reflex actions disappear. As a result, a victim who is standing may fall down. Usually, the injured person regains consciousness within a few seconds. In more severe injuries, the person may not regain full alertness for several days. After a concussion, some people develop dizziness, headaches, ringing in the ears, or changes in behavior. They also may have difficulty concentrating. Such problems may affect the person for months. For information on how to treat the victim of a concussion, see First aid (Concussion) . See also Chronic traumatic encephalopathy (CTE) .
