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Brain Concussion

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Concussion

Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD

What is concussion and what causes concussion?

Mild traumatic brain injury, or concussion, can be defined as a short-lived loss of brain function due to head trauma that resolves spontaneously. With concussion, function may be interrupted but there is no structural damage to the brain.

The brain floats in cerebrospinal fluid and is encased in the skull. These protections allow it to withstand many of the minor injuries that occur in day to day life. However, if there is sufficient force to cause the brain to bounce against the rigid bones of the skull, then there is potential for injury. It is the acceleration and deceleration of the brain against the inside of the skull that can cause the brain to be irritated and interrupt its function. The acceleration can come from a direct blow to the head or face, or from other body trauma that causes the head to shake. While temporary loss of consciousness due to injury means that a concussion has taken place, most concussions occur without the patient being knocked out. Studies of football players find that the majority aren't aware that they had sustained a head injury.

Picture of the brain and potentially brain injury areas

What are the types of concussion?

Historically, attempts to classify the severity of concussion were based on the loss of consciousness and its duration, and the presence of amnesia. It was presumed that there was a correlation between those two events and the amount of potential brain damage. The International Conference on Concussion in Sports recommended that concussion be divided into two groups: simple and complex.

Simple concussion: In a simple concussion, the person the symptoms gradually resolve, and the patient returns to normal function in 7 - 10 days.
Complex concussion: In complex concussions, symptoms persist and thought processes are affected. Patients with repeated concussions would fall into the complex category.