A concussion is an injury to the brain that results in temporary loss of normal brain function. It is usually caused by a blow to the head. Cuts or bruises may be present on the head or face, but in many cases there are no signs of trauma. Many people assume that concussions involve a loss of consciousness, but that is not true. In most cases, a person with a concussion never loses consciousness.
The formal medical definition of concussion is: a clinical syndrome characterized by immediate and transient alteration in brain function, including alteration of mental status and level of consciousness, resulting from mechanical force or trauma.
People with concussions often cannot remember what happened immediately before or after the injury, and they may act confused. A concussion can affect memory, judgment, reflexes, speech, balance, and muscle coordination. Paramedics and football trainers who suspect a concussion may ask the injured person what year it is or direct them to count backwards from 10 in an attempt to detect altered brain function.
Even mild concussions should not be taken lightly. Neurosurgeons and other brain injury experts emphasize that although some concussions are less serious than others, there is no such thing as a "minor concussion." In most cases a single concussion should not cause permanent damage. A second concussion soon after the first one, however, does not have to be very strong for its effects to be deadly or permanently disabling.
Prevalence and Incidence
Concussions are a common occurrence in sports. In the United States alone, there are an estimated 300,000 concussions annually among professional, college, and high school football players. This figure may be low because of cases that are self-treated or unreported.
Reasonable estimates show that between 4 to 20 percent of college and high school football players will sustain a brain injury over the course of one season. The risk of concussion in football is three to six times higher in players who have had a previous concussion.
A study conducted by McGill University in Montreal found that 60 percent of college soccer players reported symptoms of a concussion at least once during the season. The study also revealed that concussion rates in soccer players were comparable to those in football. According to this study, athletes who suffered a concussion were four to six times more likely to suffer a second concussion.
Concussions are also commonly caused by automobile and biking accidents, and by falls around the home, especially among toddlers and older adults.
Mild injuries to the brain like concussions may not be observable in routine neurological examinations. Diagnostic tests will typically not show any changes. Therefore, diagnosis is based on the nature of the incident and the presence of specific symptoms, confusion being a primary one. The three principal features of confusion are:
- Inability to maintain a coherent stream of thought
- A disturbance of awareness with heightened distractibility
- Inability to carry out a sequence of goal-directed movements
The following are concussion symptoms:
- Prolonged headache
- Vision disturbances
- Nausea or vomiting
- Impaired balance
- Memory loss
- Ringing ears
- Difficulty concentrating
- Sensitivity to light
- Loss of smell or taste
If any of these occur after a blow to the head, a healthcare professional should be consulted as soon as possible.
Concussions and Head Injuries
The brain normally floats inside the skull, cushioned gently by the surrounding spinal fluid. The brain consists of a gelatin-like substance and is vulnerable to outside trauma. The skull protects the brain against trauma but does not absorb all the impact of a violent force.
An abrupt blow to the head, or even a rapid deceleration, can cause the brain to bounce against the inner wall of the skull. There is a potential for tearing of blood vessels, pulling of nerve fibers and bruising of the brain substance.
Sometimes the blow can result in microscopic damage to the brain cells without obvious structural damage visible on a CT scan. In severe cases, the brain tissue can begin to swell. Since the brain cannot escape the rigid confines of the skull, severe swelling can compress the brain and its blood vessels and limit the flow of blood. Without adequate blood flow, the brain does not receive the necessary flow of oxygen and glucose. A stroke can occur. Brain swelling after a concussion has the potential to amplify the severity of the injury.
A blow to the head can cause a more serious initial injury to the brain. A contusion is a bruise of the brain involving bleeding and swelling in the brain. It can be thought of as a bruise of the brain tissue.
A skull fracture occurs when the bone of the skull breaks. A skull fracture by itself may not necessarily be a serious injury. Sometimes, however, the broken skull bones cause bleeding or other damage by cutting into the brain or its coverings.
A hematoma is a blood clot that collects in or around the brain. If active bleeding persists, hematomas can rapidly enlarge. Like brain swelling, the increasing pressure within the rigid confines of the skull due to an enlarging blood clot can cause serious neurological problems and can even be life-threatening. Some hematomas are surgical emergencies. Hematomas that are small can sometimes go undetected initially, but may cause symptoms and require treatment several days or weeks later. The warning signs of a serious brain injury are:
- Pain: Constant or recurring headache
- Motor Dysfunction: Inability to control or coordinate motor functions, or disturbance with balance
- Sensory: Changes in ability to hear, taste or see; dizziness; hypersensitivity to light or sound
- Cognitive: Shortened attention span; easily distracted; overstimulated by environment; difficulty staying focused on a task, following directions or understanding information; feeling of disorientation and confusion and other neuropsychological deficiencies.
- Speech: Difficulty finding the "right" word; difficulty expressing words or thoughts; dysarthric speech.
Seek immediate medical attention if any of these warning signs occur.
There is no universal agreement on the grades of severity for a concussion. There are many different guidelines for concussion evaluation and return to play decisions in athletes. Most guidelines recognize three different grades of concussions and share similar recommendations for return to play.
The two sets of guidelines most followed in the United States were formulated by the American Academy of Neurology (AAN) and by Robert C. Cantu, MD.
In 1986, Cantu formulated a set of guidelines that became widely used; these were subsequently adopted by the American College of Sports Medicine (ACSM). In 1991, the Colorado Medical Society Guidelines were formulated in response to several deaths related to head injuries in Colorado high school football players. These guidelines are more restrictive than previous versions and were subsequently adopted by the National Collegiate Athletic Association (NCAA). More recently, the AAN proposed another set of guidelines. Currently there is no consensus within the sports medicine community as to which set of guidelines is the most appropriate.
Grading the concussion is a helpful tool in the management of the injury (see Cantu below) and depends on: 1) Presence or absence of loss of consciousness, 2) Duration of loss of consciousness, 3) Duration of posttraumatic memory loss, and 4) Persistence of symptoms, including headache, dizziness, lack of concentration, etc.
Some team physicians and trainers evaluate an athlete’s mental status by using a five-minute series of questions and physical exercises known as the Standardized Assessment of Concussion (SAC). This method, however, may not be comprehensive enough to pick up subtle changes.
According to the Cantu Guidelines, Grade I concussions are not associated with loss of consciousness, and posttraumatic amnesia is absent or is less than 30 minutes in duration. Athletes may return to play if no symptoms are present for one week.
Players who sustain a Grade II concussion lose consciousness for less than five minutes or exhibit posttraumatic amnesia between 30 minutes and 24 hours in duration. They may also return to play after one week of being asymptomatic.
Grade III concussions involve posttraumatic amnesia for more than 24 hours or unconsciousness for more than five minutes. Players who sustain this grade of brain injury should be sidelined for at least one month, after which they can return to play if they are asymptomatic for one week.
Following repeated concussions, a player should be sidelined for longer periods of time and possibly not allowed to play for the remainder of the season.
The standard treatment for concussion is rest. For headaches, acetaminophen (Tylenol) can be taken. Postconcussive headaches are often resistant to stronger narcotic-based medications.
People who suffer a head injury may suffer from side effects that persist for weeks or months. This is known as postconcussive syndrome. Symptoms include memory and concentration problems, mood swings, personality changes, headache, fatigue, dizziness, insomnia, or excessive drowsiness. Patients with postconcussive syndrome should avoid activities that put them at risk for a repeated concussion. Athletes should not return to play while experiencing these symptoms. Athletes who suffer repeated concussions should consider ending participation in the sport.
Second-impact syndrome results from acute, often fatal brain swelling that occurs when a second concussion is sustained before complete recovery from a previous concussion. This is thought to cause vascular congestion and increased intracranial pressure, which can occur very rapidly and which may be difficult or impossible to control. The risk of second-impact syndrome is higher in sports such as boxing, football, ice or roller hockey, soccer, baseball, basketball, and snow skiing.
The CDC reports an average of 1.5 deaths per year from sports concussions. In most cases, a concussion, usually undiagnosed, had occurred prior to the final one.
Head Injury Prevention Tips
Buy and use helmets or protective head gear approved by the ASTM for specific sports 100 percent of the time. The ASTM has vigorous standards for testing helmets for many sports; helmets approved by the ASTM bear a sticker stating this. Helmets and head gear come in many sizes and styles for many sports and must properly fit to provide maximum protection against head injuries. In addition to other safety apparel or gear, helmets or head gear should be worn at all times for:
- Baseball and Softball (when batting)
- Horseback Riding
- Powered Recreational Vehicles
Head gear is recommended by many sports safety experts for:
- Martial Arts
- Pole Vaulting
- Supervise younger children at all times, and do not let them use sporting equipment or play sports unsuitable for their age.
- Do not dive in water less than 9 feet deep or in above-ground pools.
- Follow all rules at water parks and swimming pools.
- Wear appropriate clothing for the sport.
- Do not wear any clothing that can interfere with your vision.
- Do not participate in sports when you are ill or very tired.
- Obey all traffic signals, and be aware of drivers when cycling or skateboarding.
- Avoid uneven or unpaved surfaces when cycling or skateboarding.
- Perform regular safety checks of sports fields, playgrounds and equipment.
- Discard and replace sporting equipment or protective gear that is damaged.
- Wear a seatbelt every time you drive or ride in a motor vehicle.
- Never drive while under the influence of drugs or alcohol or ride as a passenger with anybody else who is under the influence.
- Keep firearms unloaded in a locked cabinet or safe, and store ammunition in a separate, secure location.
- Remove hazards in the home that may contribute to falls. Secure rugs and loose electrical cords; put away toys; use safety gates; and install window guards. Install grab bars and handrails if you are frail or elderly.
Copyright, the American Association of Neurological Surgeons, November 2005.