Definition of Concussion

A concussion is a brain injury that may result in a bad headache, altered levels of alertness, or unconsciousness.

Causes, incidence, and risk factors

There are more than a million cases of concussion each year in the United States.


Concussions don’t always involve a loss of consciousness. In fact, most people who have concussions never black out. Some people have had a concussion and never even realized it.

Signs and tests

A neurological examination may show abnormalities. The doctor will check your pupil size.


A health care provider will do a brain and nervous system (neurological) evaluation to determine the right treatment for an uncomplicated concussion.

Expectations (prognosis)

Full recovery is expected from an uncomplicated concussion. Dizziness, memory loss, problems thinking, irritability, headaches, sleep disturbances, and other symptoms may occur continue for weeks or even months afterwards.


Jacob L. Heller, MD, Emergency Medicine, Virginia Mason Medical Center, Seattle, Washington, Clinic. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 3/18/2010


ADAM Medical Encyclopedia

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