A concussion is a traumatic head injury that occurs when the brain shifts inside of the skull, often coming into contact with the skull. Concussions usually occur when the head hits a hard surface, which may occur during an accident or sporting event. It's a common misconception that a person loses consciousness when he or she suffers a concussion, but this is not always the case. While severe concussions often cause a patient to lose consciousness, milder ones may not.

Even a mild concussion can have lasting side effects, which include headaches, fatigue and loss of memory. Sometimes concussions that initially seem minor cause severe bleeding on the brain -- this can lead to death if not treated properly. Thus, it is important for anyone who suffers a concussion, no matter how mild, to head to the ER or at least seek prompt medical treatment . Being aware of the common symptoms of a mild concussion can help you recognize this injury in yourself or a loved one, so you know when to seek care.

Confusion and Mental Fog

Often, after a concussion, a patient will feel mildly to moderately confused. He or she may not remember hitting the head. Sometimes calling up memories and answers to simple questions takes a little longer than normal. The person may insist he or she is okay, but if you think he or she seems a little "slow" and out of sorts, insist on seeking medical attention.

Slurred Speech

If you or someone you know is experienced slurred speech after hitting the head, there's a good chance of a concussion. Sometimes only certain words or sounds may sound slurred, while other times all speech may sound as if the person is drunk.

Headache

"I don't have a concussion, I just have a headache because I hit my head" is a common phrase uttered by athletes and others whose heads collide with solid objects. However, if someone has a headache after hitting his or her head, this is actually a sign of a concussion. Sometimes the headache does not develop right away. Even if it shows up an hour or two after the event, it's best to head to the emergency room.

Nausea and Vomiting

Sometimes the head feels just fine after a concussion, but the person experiences a lot of nausea and vomiting. These symptoms are often overlooked, as they don't seem to be related to a head injury -- but they are. The concussion can put pressure on the nerves leading to the digestive tract, leading to feelings of nausea.

Ringing in the Ears

A high-pitched ringing sound after hitting the head is indicative of a concussion. Sometimes this is the only symptom patients experience initially, but it's important to seek treatment promptly because other more serious symptoms may appear.

Disordered Sense of Smell and Taste

This symptom may not present itself until a few hours after the concussion when the person attempts to eat. Some concussion patients think they smell obnoxious odors that no one else smells. Others suddenly find that their favorite foods taste terrible.

Sensitivity to Light and Sound

If you notice someone does not want to be around bright lights or is reacting negatively to loud noises after hitting the head, he or she probably has a concussion.

Loss of Balance

This symptom appears more often in children than adults. You may notice that the person sways as he or she walks, or needs to hold onto something or someone in order to walk.

If you or someone you know experiences any of the symptoms above, seek medical care promptly. It's hard to know how severe a concussion is without a complete medical evaluation. Even if the individual turns out to be perfectly fine, you're always better off safe than sorry when it comes to head injuries.