(HealthDay News) -- A jarring and forceful blow to the head can result in a brain injury called a concussion.

The American Academy of Family Physicians lists the following warning signs of concussion, which should be evaluated as soon as possible by a doctor:

• Headache.
• Difficulty seeing.
• Dizziness.
• Difficulty concentrating, memory loss or confusion.
• Problems retaining balance.
• Nausea.
• Ringing in the ears.