While most sport-related concussions are mild, the potential always exists for a more serious, life-threatening head injury, such as an epidural hematoma (bleeding between the skull and the brain).
Because studies have shown that athletes at the collegiate and high school level may demonstrate neuropsychological deficits that are not be picked up in a sideline assessment, and are more likely to have delayed onset of symptoms  it is particularly critical that an athlete suspected of having a concussion not be left alone and should be monitored by a parent or other responsible adult during the first 24 to 48 hours for signs that require immediate hospitalization 
An athlete must go to a hospital emergency room if he or she:
- has a headache that gets worse and does not go away
- Is very drowsy or can't be awakened (woken up)
- Can't recognize people or places
- Is vomiting repeatedly
- Behaves unusually,
- Becomes increasingly, restless or agitated
- Experiences convulsions or seizures (arms and legs jerk uncontrollably)
- Has weak or numb arms or legs
- Is unsteady on their feet
- Has slurred speech
- Has one pupil which is larger than the other
- Loses consciousness (even briefly)
- Will not stop crying/cannot be consoled, or
- Their symptoms get worse.
The advice to parents: err on the side of caution.
1. McCrory P, et al. Concussion Statement on Concussion in Sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012. Br J Sports Med 2013;47:250-258.
2. Sports Concussion Assessment Tool 3. Br J Sports Med 2013;47:259.
3. Pocket Concussion Recognition Tool. Br J Sports Med 2013;47:267.
Revised November 3, 2015