Skip to main content Skip to Search Box
Summary Article: Concussion
from The Brain, the Nervous System, and Their Diseases

Concussion means “to shake violently” or “action of striking together” in Latin. A concussion is the most common type of traumatic brain injury (TBI), although it is a very minor form of TBI. Concussions are often seen in sports like football, hockey, and cycling as well as car accidents and falls. A concussion is defined as a head injury with temporary loss of brain function. Impact forces from the accident could cause concussions where the head strikes something.

Grading System

When diagnosing a concussion, health care professionals use a common grading system, which is based on the severity of the head injury. The decision on whether or not to allow athletes to continue to play depends on this grading system following a head injury. In fact, in some states, such as Colorado, it is the law that an athlete cannot return to play after any kind of head injury until he or she has been released by a health care professional (Colorado Legislature, 2011). The American Academy of Neurology employs the following grades. A grade I concussion includes confusion with symptoms lasting less than 15 minutes and no loss of consciousness. A grade II concussion includes symptoms lasting longer than 15 minutes and no loss of consciousness. Finally, a grade III concussion includes loss of consciousness. For grade III concussion, there are two subcategories where grade IIIa is a loss of consciousness that lasts for seconds and grade IIIb is a loss of consciousness that lasts for minutes.

Brain trauma, possibly resulting in concussion.


Signs and Symptoms

Signs and symptoms of a concussion include both physical and cognitive/emotional aspects. A headache is the most common physical sign. Other physical signs and symptoms can include but are not limited to dizziness, nausea, and vomiting, lack of motor coordination, or difficulty balancing. Visual symptoms can include but are not limited to light sensitivity, seeing bright lights, or blurred vision. Ringing in the ears (tinnitus) is also reported. Finally, cognitive symptoms include confusion, disorientation, and difficulty focusing attention. Loss of consciousness could also occur but studies have shown that it is not correlated with the severity of the concussion. Other symptoms could include changes in sleeping patterns and difficulty with reasoning. Since there is a wide range of symptoms it is important to receive care from a health care provider as soon as possible.


A patient's head is always first examined to be sure there is not a more serious head injury like intracranial bleeding. Diagnosis of a concussion is usually based on duration of unconsciousness (less than 30 minutes) and post-traumatic amnesia (less than 24 hours; Hayden et al., 2007). A clinician first determines if there is an altered level of consciousness (LOC) following a head injury. LOC represents a state of brief coma when someone is typically unresponsive to external stimuli. Typical scans such as computed tomography (CT), magnetic resonance imaging (MRI), and electroencephalograms (EEG) are not helpful in determining effects of a concussion because they do not show up on such scans. This is due to the fact that a concussion is a metabolic injury instead of a structural injury. Diagnosing a concussion can be extremely difficult as it shares symptoms with many other conditions.


Today, the best way to prevent concussions is employing general safety measures like wearing a seatbelt when in a moving vehicle, wearing a helmet when playing contact sports or biking, keeping floors clear of clutter, and possibly wearing shoes that do not interfere with balance. The latter two safety measures may prevent accidental falls.


Observation of a concussion patient is critical for several hours after the injury. The key treatment following a concussion is just rest. Activities like driving, texting, schoolwork, and video games are some activities that should be reduced. Plenty of nighttime sleep as well as daytime rest is often prescribed following a concussion. Medications may be prescribed to help with sleep problems and the headaches. Acetaminophen (Tylenol) is typically recommended for a headache due to concussion, because ibuprofen (Advil) and aspirin may increase the chance of intracranial bleeding.

Post-Concussion Syndrome

Post-concussion syndrome occurs when symptoms of a concussion do not resolve for weeks, months, or even years after the initial injury. The most common symptoms are headaches, dizziness, fatigue, sleep problems, and irritability. Symptoms typically go away on their own but may persist for longer periods of time.

Second Impact Syndrome

Second impact syndrome results from acute, often fatal brain swelling that can occur if a second concussion is sustained before complete recovery from a previous concussion. This can cause increased intracranial pressure and vascular congestion. It can occur rapidly and tends to be very difficult to control. The risk of second impact syndrome is extremely high in contact sports like football, hockey, and boxing. Death may occur from a second concussion, particularly when a person had an undiagnosed concussion that was not healed completely before the second concussion occurred.


A research study was completed at the American Academy of Neurology on the effects of repeated mild head impacts in contact sports like football and hockey (Clark, 2012). The study was performed in order to try and explain what brain functions become damaged after numerous mild head impacts (concussions). The study included division I football and hockey players in which a device was placed in their helmets to record the force and time of impact during their entire season. These athletes were then tested on their memory, concentration, and problem solving among other tasks. Their results showed no significant difference from preseason cognitive testing to postseason cognitive testing even though they were impacted on average 470 times. This study was important in determining if even short-term cognitive function among athletes was changed after receiving many impacts over a single season.

See also Conscious and Consciousness; Dizziness and Vertigo; Headache; Trauma

Further Reading
  • Centers for Disease Control and Prevention (CDC). (2011). Concussion and mild TBI. Retrieved from
  • Clark, D. (2012). Effects of repeated mild head impacts in contact sports: Adding it up. Neurology, 78 e140-e142. Retrieved from
  • Colorado Legislature. (2011). Senate Bill 11-040. Retrieved from
  • Hayden, M. G.; Jandial, R.; Duenas, H. A.; Mahajan, R.; Levy, M. (2007). Pediatric concussions in sports: A simple and rapid assessment tool for concussive injury in children and adults. Child's Nervous System, 23(4), 431-435.
  • Renee Johnson
    Copyright 2014 by Jennifer L. Hellier

    Related Articles

    Full text Article Sport-Related Concussion
    Brain Injury Medicine: Principles and Practice

    INTRODUCTION Concussions are common in sports (1–3). Moreover, these injuries might be more prevalent than initially thought because some concuss

    Full text Article Concussion
    Gale Encyclopedia of Nursing and Allied Health

    Definition Concussion is a trauma-induced change in mental status, associated with confusion and amnesia, that may or may not be accompanied by a

    Full text Article Concussion in Sports
    Clinical Sports Psychiatry: An International Perspective

    KEY POINTS Concussion results from a sudden impact to the brain induced by (direct or indirect) traumatic biomechanical forces. Concussion does no

    See more from Credo