Concussion - An Introduction

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What is Concussion?

A concussion is a blow to the head or body that causes the brain to shake inside the skull. This can change the way your brain normally works. It is sometimes called a mild traumatic brain injury. It is also sometimes called minor head injury. A concussion can result from any kind of blow, such as a car crash, a sports injury, a fall or an assault. There is no single universal definition of concussion, but most professionals accept that for an injury to be classified as mild or minor, the person must be unconscious for 30 minutes or less (sometimes this figure is quoted as 20 minutes and sometimes 15 minutes). It is possible to be concussed without losing consciousness.

What are the symptoms?

Concussion symptoms can include:

  • Headaches
  • Weakness
  • Numbness
  • Decreased coordination or balance
  • Confusion
  • Nausea
  • Slurred speech
  • Vomiting

Sometimes people complain of “just not feeling like themselves.” If you or a loved one notices any of these symptoms, you should seek medical attention immediately.

How long do symptoms last?

Recovery times from concussion vary. For most people, the symptoms are temporary and may resolve in a few hours or days. For a few people the effects can be much more severe and longer lasting. When the effects of a head injury persist in this way, over weeks, months or sometimes years, the person may be experiencing Post Concussion Syndrome.

Post Concussion Syndrome (PCS)

Post Concussion Syndrome is a complex disorder in which various symptoms — such as headaches and dizziness — last for weeks and sometimes months after the injury that caused the concussion. Most people recover from concussion relatively quickly within a few hours or days with rest and sleep. Most people are able to return to work within two weeks of the injury. Symptoms can last longer for some people, and can seem more severe than perhaps a casual observer would guess from the initial injury. Post Concussion Syndrome describes the situation where someone is experiencing the more severe and long lasting after-effects of a relatively mild blow to the head.

Diagnosing Post Concussion Syndrome is hard. The symptoms are also associated with other problems, including work or relationship stress, drug and alcohol issues, depression, a virus, or a more serious psychological or psychiatric problem. Whether you get Post Concussion Syndrome or not does not appear to be linked to the severity of the injury. Some people experience many concussions and do not get PCS. Risk factors for Post Concussion Syndrome include:

  • Multiple previous head injuries
  • A history of serious emotional or psychiatric problems
  • Alcohol or solvent abuse
  • A demanding occupation
  • Age (children, teenagers, and the elderly are more vulnerable) 

For more information on Post concussion syndrome, see this page at which also has a factsheet for download.

Is a Concussion Dangerous?

A concussion or Mild Traumatic Brain Injury is rarely dangerous on its own and does not result in death. However, having a concussion can be a risk factor for more serious conditions, such as Second Impact Syndrome or for Chronic Traumatic Encephalopathy.

Although most concussions result in only temporary effects, all concussions should be taken seriously. If you experience a concussion in the course of sporting activity for example, make sure you get medical attention immediately. There are guidelines for various sports to ensure that you do not put yourself in further danger.

What is Second Impact Syndrome?

Second impact syndrome describes the situation in which an individual gets a second injury before the symptoms from a previous concussion have resolved. In the case of second impact syndrome, the brain swells rapidly and dangerously, resulting in death or severe brain injury.

Second Impact Syndrome is rare, but it is often fatal.

What is Chronic Traumatic Encephalopathy (CTE)?

Chronic Traumatic Encephalopathy (CTE) is a progressive disease of the brain found in athletes and other people with a history of repeated head injury, including concussions. The symptoms include memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, and, eventually, progressive dementia.

CTE historically has been most associated with boxing and American Football, but more recent studies have identified other sports which present risk of CTE, including Rugby, Football, Hockey, Wresting, Equestrian sports and others.

What Guidelines are there for Concussion in Sport?

International Guidelines

The international community have agreed an overall approach to dealing with concussion in sport, which is contained in this document:

Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012

For the Irish response, see our news item on the Joint Oireachtas Committee for Health report on Concussion in Sport.


Rugby’s governing body in Ireland , the IRFU have an excellent brochure on the management of concussion at

and a section on their website at has much useful material


The GAA website has an extensive section on the management of concussion at


The FAI has  a section on their website devoted to management of concussion at


The Irish Hockey Association has a set of guidelines at

Concerned about concussion?

If you think you may be suffering from the effects of concussion, seek medical help immediately. Consult a doctor or your GP. If you have prolonged aftger-effects from a blow to the head, see the section on Post Concussion Syndrome above. 

Tools and Resources

The SCAT3 (Sport Concussion Assessment Tool) is available from

Download the " Concussion Smart" App (for iOS) by Acquired Brain Injury Ireland from the App store on

The Neuropsychology of Concussion

Slides from a recent presentation by Dr. Elaine Kelly at the conference "Sports Injuries, Concussion and the Law", Dublin 2015