The death of a 42 year old man on a roller coaster at Six Flags Over Georgia this week has sharpened questions about amusement park safety. Reports of other serious roller coaster injuries, including cases requiring emergency brain surgery, have added urgency to those concerns.

Six Flags Over Georgia was set to reopen Friday. CNN wellness expert Dr. Leana Wen, an emergency physician and clinical associate professor at George Washington University, explained the potential health risks riders should consider.

Wen said serious injuries are uncommon when compared with the enormous number of amusement park rides taken each year. According to the International Association of Amusement Parks and Attractions, the chance of suffering a serious injury on a ride at a fixed site US amusement park is approximately one in 15.5 million rides.

That figure has important limitations. It covers all amusement park rides rather than roller coasters alone, not every injury is necessarily reported, and the data comes from an entity sponsored by the industry.

There is also no independent national database that captures every amusement park injury and death. That absence makes the available statistics useful but incomplete when assessing the risks associated with roller coasters.

Roller coasters subject riders to substantial physical forces through rapid acceleration, deceleration, sudden drops and abrupt changes in direction. G forces can increase or decrease the pressure riders feel, while collisions, restraint problems and other mechanical or operational incidents can also cause severe injuries.

The cause of an injury must be distinguished from the circumstances surrounding it. The investigation into the Six Flags Over Georgia death remains ongoing, and its cause is not known to be the same as the mechanism behind brain injuries reported on another Six Flags roller coaster.

A rider does not have to strike their head to suffer a serious brain injury. Sudden acceleration, deceleration or directional changes can make the head move abruptly, causing the brain, which is suspended in fluid inside the skull, to shift relative to surrounding structures.

One possible result is a subdural hematoma, which involves bleeding between the brain and its outer protective covering. The bleeding can place pressure on the brain and represents a very serious injury.

Several riders suffered that injury after riding the X2 roller coaster at Six Flags Magic Mountain in California, including two who required emergency brain surgery. Other potential injuries include concussions, damage to brain tissue and bleeding around or within the brain.

Some brain injury symptoms may resolve over time, but other cases can result in permanent neurological damage or death. The range of possible outcomes makes unusual or worsening symptoms after a ride especially important to recognize.

Jerking movements can also strain the muscles and ligaments supporting the neck, producing neck pain, stiffness and headaches similar to whiplash symptoms after a car accident. Symptoms may begin immediately or emerge later that evening or the following day.

Dizziness, nausea and motion sickness are more common but less serious. They occur when the brain receives conflicting information from the eyes and the balance organs in the inner ear, and they usually fade shortly after the ride ends.

A far rarer but extremely serious risk is cervical artery dissection, a tear in the inner lining of an artery supplying blood to the brain. Sudden neck movements can contribute to this potentially life threatening condition, which can cause a stroke.

People with significant neck or back conditions, spinal instability, recent orthopedic injuries or recent surgery may face greater risks. Those with unstable heart disease, serious arrhythmias or poorly controlled high blood pressure should avoid rides carrying warnings about those conditions.

People with known brain aneurysms, previous strokes or serious neurological conditions should consult their physicians before riding. Additional caution applies to people taking blood thinning medications, pregnant women and families ensuring that children meet every height and restraint requirement.

A sudden severe headache, repeated vomiting, confusion, unusual sleepiness or vision changes require emergency medical care. Sudden weakness, numbness, facial drooping, difficulty speaking, loss of balance, trouble walking or severe neck pain accompanied by neurological symptoms also demand immediate evaluation.

Symptoms can appear hours after someone has left the amusement park, so persistent or worsening headache or neck pain should not be dismissed. Riders can alert amusement park staff for help finding an emergency room or calling 911.

Before boarding, riders should review posted safety rules, physical requirements and health warnings. People with underlying medical issues should seek guidance from their clinicians about which attractions to avoid.

Millions of people enjoy amusement parks each year without injury, and available statistics indicate that severe harm is rare. Still, the fastest and most intense roller coasters carry risks, and visitors can choose less demanding attractions based on their health, preferences and comfort.