Hospital Medicine


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I. What every physician needs to know.

Concussion is a form of brain injury that may result from a direct blow or from rapid rotation, acceleration and/or deceleration of the brain inside the skull. Concussions differ from other forms of traumatic brain injury in that there is no apparent structural damage to the brain parenchyma, no intracranial hemorrhage, and no skull fracture but there is an alteration of the cellular processes in the brain. These perturbations of cellular function cause the concussive phenomenon.

Concussion can occur without direct impact or loss of consciousness, and can result in physical, cognitive or emotional symptoms that are evident immediately or evolve over hours, days or weeks.

There are no studies of concussion in hospitalized patients, so recommendations for concussion evaluation and management are typically adopted from the sports literature.

Sports medicine has defined most of the practice guidelines for concussion. Patients with physical disabilities, psychiatric illness, dementia, or altered mental status at baseline may require modified evaluation or closer observation.

The 3rd International Conference on Concussion in Sport, held in Zurich in 2008, offers a revised consensus statement on concussion in sport, which may help in evaluation of both outpatients and inpatients. “Concussion is defined as a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces."

Several common features that incorporate clinical, pathologic, and biomechanical injury constructs that may be utilized in defining the nature of a concussive head injury.

  • Concussion may be caused by either a direct blow to the head, face, or neck or a blow elsewhere on the body with an “impulsive” force transmitted to the head.

  • Concussion typically results in the rapid onset of short-lived impairment of neurologic function that resolves spontaneously.

  • Concussion may result in neuropathological changes, but the acute clinical symptoms largely reflect a functional disturbance rather than structural injury.

  • Concussion results in a graded set of clinical syndromes that may or may not involve loss of consciousness. Resolution of the clinical and cognitive symptoms typically follows a sequential course. In a small percentage of cases, however, post-concussive symptoms may be prolonged.

  • No abnormality on standard structural neuroimaging studies is seen in concussion.

Postulated causes for the mechanism of concussion include microscopic axonal injury leading to impaired axonal transport and edema, release of neurotransmitters (acetylcholine, glutamate, aspartate) and cytotoxic edema of white matter tracts.

Grading a concussion is a helpful tool in the management of the injury and depends on: 1) presence of loss of consciousness, 2) duration of loss of consciousness, 3) duration of post-concussive amnesia, and 4) persistence of post-concussive symptoms. Though there is no consensus on concussion grading, the two most commonly used guidelines for concussion in sport are the American Association of Neurology guidelines and Cantu guidelines.

For athletes, grade of injury helps establish a safe back-to-play plan and may help predict duration of recovery.

Cantu Guidelines for concussion in sport by neurosurgeon Dr. Robert Cantu are as follows:

  • Grade I – no associated loss of consciousness, amnesia absent or lasting less than 30 minutes.

  • Grade II – loss of consciousness less than 5 minutes duration, amnesia lasting between 30 minutes and 24 hours

  • Grade III – loss of consciousness for more than 5 minutes, amnesia lasting longer than 24 hours

Some concussions are associated with seizures that occur at the time of trauma or up to 1 week after the traumatic event. These seizures are generally treated with anti-epileptic therapy in the acute setting and then weaned over several weeks after seizure event, mainly to prevent status epilepticus that is associated with increased mortality. It is controversial whether or not these early seizures result in or are associated with post-traumatic epilepsy.

Grade of injury correlates with the likelihood of seizure, and warrants neuroimaging to evaluate for intracranial hemorrhage or depressed skull fracture. Seizures can develop any time after a brain injury event, but the majority occur within 2 years of the injury and represent post-traumatic epilepsy.

Occasionally, concussions may be associated with transient cortical neurologic deficits, such as global amnesia or cortical blindness. These deficits are thought to be secondary to vasospasm and may be a trauma-induced migraine equivalent.

Second impact syndrome results from acute and sometimes fatal cerebral edema that can occur when a patient sustains a repeated concussion before complete recovery from a previous concussion. This may be due to vascular congestion and increased intracranial pressure, which can occur very rapidly. Similar to risk of concussion in sport, the risk of second-impact syndrome is higher in impact sport.

A concussion can be complicated by a brain contusion that can be associated with localized ischemia, edema, and development of intracranial hemorrhage. Signs of a cortical contusion vary depending on size, number, and location and may delay recovery from concussion.

Concurrent research in adult concussion indicates metabolic and cognitive processes return to a pre-concussed state after 7-10 days in the majority of concussed individuals. Approximately 10% of patients have persistent symptoms of concussion that comprise the post-concussion syndrome.

The Diagnostic and Statistical Manual of Mental Disorders (DSM IV) defines this syndrome as cognitive deficits in attention or memory and at least three additional symptoms, such as fatigue, insomnia, headache, dizziness, irritability, mood disturbance, apathy, or personality changes. These symptoms can last for months after a concussion and are difficult to distinguish from other diagnoses such as major depression disorder.

II. Diagnostic Confirmation: Are you sure your patient has concussion?

Concussion is a clinical diagnosis that relies on a history of injury reported by a patient or a witness of an event, and the presence of post-injury physical examination findings and symptoms listed below.

Assessment may be complicated in a patient with dementia, psychiatric disease or altered mental state at baseline. Computed tomography (CT) and magnetic resonance imaging (MRI) neuroimaging is normal in most concussions, though is indicated in patients suspected of having an intracranial hemorrhage, focal neurological deficits, associated seizure, or prolonged loss of consciousness (see imaging studies in the diagnostic evaluation below). Concussion should be graded on severity of injury, symptoms, and length of symptoms. Worsening of symptoms or recurrence after resolution can signal a higher-grade injury than upon original evaluation.

A. History Part I: Pattern Recognition:

A patient with suspected concussion typically has a history of a trauma or impact that may result in rapid acceleration and deceleration of the patient or head of the patient, such as motor vehicular accident, fall, occupational or recreation accident, or battery. Any of these events followed by a witnessed loss or change in consciousness, seizure, or onset of symptoms described below, should raise suspicion for concussion or another type of brain injury. The majority of concussions are not accompanied by loss of consciousness but often result in self-reported symptoms that may be missed unless specifically evaluated. Concussion should also be suspected in any patient with face, head, or neck injury.

A patient with an acute concussion may report symptoms of headache, neck pain, dizziness, nausea, vomiting, confusion, anterograde or retrograde amnesia, blurred vision, tinnitus, and sensitivity to noise and light. Though many of these symptoms can be transient, headache can persist for hours to months depending on the severity of injury. Over the course of hours or days, the patient may develop additional symptoms. These typically include ongoing memory disturbances, decreased concentration, increased emotionality, sleep disturbances including both insomnia and hypersomnia, mood changes, personality changes, disinhibition, and fatigue. Patients may also report feeling in a fog or slowed down.

For most concussed individuals, symptoms improve or resolve within 7-10 days. Symptoms may worsen or recur after resolution with increased physical exertion, or cognitive or psychological stress. Ongoing symptoms may signal that a patient needs to extend the period of brain rest. If symptoms persist after a month of rest (see treatment below), suspect a more serious injury than originally diagnosed such as a higher grade concussion, mild traumatic brain injury, or onset of post-concussion syndrome. Post-concussion syndrome is characterized by fatigue, headaches, equilibrium disturbances or difficulty in concentrating that may persist for weeks to months after the initial injury. A patient with ongoing symptoms two weeks after injury should be referred for neuroimaging and neuropsychological testing.

B. History Part 2: Prevalence:

It is difficult to accurately estimate incidence and prevalence of concussions. Most concussed individuals do not seek medical attention, especially if their symptoms are mild or improve quickly. Estimates of the number of persons with all types of brain injury ranges from 1.5 to 2 million, with 80% of injuries considered mild at time of evaluation in the emergency department. According to the Centers for Disease Control nd Prevention (CDC), children aged 0 to 4 years, adolescents aged 15 to 19 years, and adults aged 65 years and older are most likely to sustain a traumatic brain injury (TBI). Adults aged 75 years and older have the highest rates of TBI-related hospitalization and death. Men have higher rates of concussion in all age groups.

The highest at-risk groups for concussion include athletes in high-impact sports such as football, ice hockey, soccer, boxing, field hockey, lacrosse, and rugby. In the general population, concussions most frequently result from motor vehicle accidents, falls, cycling-related injuries, and battery. Unfortunately, patients with previous concussions are at increased risk of repeat concussions, and are most susceptible during the post-concussion period. Those with three or more prior concussions are also at an increased risk of developing post-concussion syndrome, as are women, patients over age 40, and those with history of depression.

C. History Part 3: Competing diagnoses that can concussion.

Loss of consciousness in a concussed individual, lasting greater than 5 minutes and Glasgow Coma Scale (GCS) less than 15, can also meet criteria for mild traumatic brain injury, which may result in long-term or permanent cognitive impairment. Similar to concussion, an intracranial hemorrhage can present with history of trauma and symptoms including headache, nausea, dizziness, seizure, and loss of consciousness, but evolves with worsening of symptoms, such as decreased level of consciousness and neurologic deficits, and it requires immediate intervention. Other conditions that may share features with concussions include migraine, headache, stroke, transient ischemic attack (TIA), seizure, brain contusion, tumor, metabolic encephalopathy, and skull fracture without brain injury.

Migraines and other headaches can only be distinguished from concussion by history, context, and observation over time. Neuroimaging is warranted if stroke, TIA, brain contusion, seizure, tumor, or skull fracture is suspected. Seizure foci may or may not be evident on neuroimaging, though all new onset seizures require thorough evaluation. Metabolic encephalopathy from prescribed or self-administered substances, electrolyte derangement, renal and hepatic failure, bacteremia, or other acute illness can result in symptoms similar to those of a concussion but should be suspected particularly if abnormal vital signs are present. As with seizure and syncope, it is sometimes difficult to ascertain the sequence of events that may have led to a fall in an unwitnessed event.

D. Physical Examination Findings.

Common general physical examination findings of an acutely concussed patient can include altered state of consciousness or brief loss of consciousness, seizure, postictal state, confusion, anterograde or retrograde amnesia, inattention, unsteady gait, slurred speech, vacant stare, agitation, or irritability.

A thorough neurologic examination should include a Glasgow Coma Scale, cranial nerve exam, sensory exam including proprioception. Some patients may have cortical blindness or blurred vision, may report tinnitus or hearing difficulties. Evaluation may reveal abnormal gait, positive Romberg, and decreased strength or coordination in upper or lower extremities.

Non-verbal patients or those with an altered mental status at baseline should be assessed for listlessness, increased fatigue or hypersomnolence, agitation, vomiting, change in eating habits, increased unsteadiness, or decreased independence with self-care tasks.

In a patient who is verbal and does not have an altered mental status at baseline, perform a cognitive assessment with a tool to test orientation, immediate memory, and concentration such as the Standardized Assessment of Concussion (SAC) test. This tool is best utilized in combination with other tools such as symptoms, reaction time, and thorough physical examination —see diagnostic tests below—in emergency departments and in athletes suspected of having a concussion during competition.

If the patient remains in the hospital, nursing staff should be asked to monitor symptoms (see above) every four hours. The patient should also be reassessed by a physician with a repeat physical exam 24 hours after injury.

E. What diagnostic tests should be performed?

Evaluate for symptoms, documenting severity (mild, moderate or severe) for each of: headache, nausea, vomiting, dizziness, poor balance, blurred or double vision, sensitivity to light, sensitivity to noise, tinnitus, difficulty concentrating, feeling slowed down, fatigue, feeling depressed, agitation or irritability, amnesia (if present, document length and anterograde or retrograde).

Standardized Assessment of Concussion (SAC)

The orientation test consists of five questions, scoring one point for each correct answer for a total of 5 points:

  • “What month is it?”

  • “What is today’s date?”

  • “What is the day of the week?”

  • “What year is it?”

  • Reassess within an hour with “What time is it right now?”

The immediate memory test consists of three trials testing recall of five word threads after reading statements at a rate of one word per second. Score one point for each correct response for a total of 15 points.

  • Trial 1: “I am going to test your memory. I will read you a list of words and when I’m done, repeat back as many words as you can remember, in any order.” Sample words to choose from: elbow, apple, carpet, saddle, bubble, candle, paper, sugar, sandwich, wagon, baby, monkey, perfume, sunset, icon, finger, penny, blanket, lemon, insect

  • Trial 2 and 3: “I am going to repeat the same list again. Repeat back as many words as you can remember in any order, even if you said the word before.”

Concentration test consists of two exercises for a total of 5 points. In the first exercise, the physician reads a string of numbers and asks the patient to repeat them backwards in the reverse order to which they were read. For example, if the physician reads 7–1–9, the patient would say 9–1–7. There are four sequences, each valued at 1 point. The first trial should have a sequence of three numbers, increasing each sequence length by one digit if the patient is able to complete this exercise correctly. If the patient is unable to complete a sequence after two trials, discontinue this exercise.

The second concentration test requests the patient to list the months of the year in reverse order starting with December. The entire sequence is valued at 1 point. After completion of this section, ask the patient for the list of words from the immediate recall assessment for a delayed memory evaluation of the string of five words for an additional 5 points.

The SAC test has a maximum total of 30 points, and the majority of non-concussed patients score between 25 to 30 points. In a patient with history consistent with concussion and previously normal mental status, a score of less than 25 may be consistent with injury.

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

There are no laboratory tests helpful in evaluation for concussion at this time.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Concussion is not associated with abnormal findings on neuroimaging. However, it is imperative to evaluate the risk of intracranial hemorrhage in all patients presenting with possible concussion or traumatic brain injury, and to obtain neuroimaging in at-risk patients. The American College of Emergency Physicians (ACEP) and the Centers for Disease Control and Prevention (CDC) formed a panel to evaluate and guide clinical policy on neuroimaging and clinical decision-making in adults presenting to the emergency department with mild traumatic brain injury. Their advice is set put below.

“A non-contrast head CT is indicated in head trauma patients with loss of consciousness or post-traumatic amnesia only if one or more of the following is present: headache, vomiting, age greater than 60 years, drug or alcohol intoxication, deficits in short-term memory, physical evidence of trauma above the clavicle, post-traumatic seizure, GCS score less than 15, focal neurologic deficit, or coagulopathy. A non-contrast head CT should be considered in head trauma patient with no loss of consciousness or post-traumatic amnesia if there is a focal neurologic deficit, vomiting, severe headache, age 65 years or greater, physical signs of basilar skull fracture, GCS score less than 15, coagulopathy, or dangerous mechanism of injury (for example, ejection from a motor vehicle, a pedestrian struck, and fell from a height of more than 3 feet or 5 stairs).”

Other tests such as positron emission tomography, structural MRI, functional MRI, diffusion tensor imaging may provide additional information but are still in the research phase of clinical utility.

F. Over-utilized or “wasted” diagnostic tests associated with this diagnosis.

In patients with no risk factors for intracranial lesions, neuroimaging is very unlikely to yield positive findings in in the emergency department setting. However, there are no studies in concussion in hospitalized patients to guide practice.

III. Default Management.

Physical and cognitive rest is key to concussion recovery. The patient should be instructed to avoid strenuous physical and cognitive activities for at least 24 hours or until previous symptoms are completely resolved as such activity can delay recovery. These activities include reading, checking e-mail, watching television, engaging in stressful discussions or decision making.

If a patient is discharged prior to complete resolution of concussion symptoms, give instruction not to operate machinery, including cars and even bicycles. The patient should also avoid alcohol, benzodiazepines, non-steroidal anti-inflammatory drugs (NSAIDs), and narcotics or other medications that can increase the risk of bleeding, alter mental status, or increase risk of seizure. In the inpatient setting, symptom management may include triptans and topiramate prophylaxis for headache, and anti-emetics such as ondansetron for nausea. Opiates can be used for severe headache. Appropriate acute symptom management may decrease likelihood of post-concussion syndrome.

A. Immediate management.

There are no interventions that can reverse injury or symptoms of concussion. The concussed patient should be advised to rest in a dark room, and to minimize noise and unnecessary interruptions. Headache is the most common symptom of concussion and should be managed with acetaminophen and triptans if possible. Ondansetron may be used for nausea. Avoid medications that lower seizure threshold and are associated with increased bleeding. Medications that alter mental status such as opiates or benzodiazepines can be very useful in an observed setting. Nursing staff should obtain neurological checks every 4 hours during the initial 24 hours after trauma. If the patient has a safe discharge plan, a responsible caregiver needs to assess the patient every 4 hours for the first 24 hours.

B. Physical Examination Tips to Guide Management.

In hospitalized patients, repeat evaluation of symptoms and neurological exam including cranial nerve exam, strength, gait, Romberg, and SAC or similar test (if applicable) should be repeated 24 hours after initial event. A decline in function, focal neurologic deficits, or lack of improvement may signal that the initial diagnosis was not consistent with concussion.

C. Laboratory Tests to Monitor Response To, and Adjustments in, Management.

There are no laboratory tests to evaluate or monitor for concussion at this time.

D. Long-term management.

Patients with concussion should be instructed to remain on cognitive and physical rest for at least 24 hours or until symptoms are completely resolved prior to increasing their level of activity. Once symptom-free, the patient can increase the level of activity to include low-impact physical exertion not requiring agility or balance. If symptoms recur, activity should be immediately discontinued until symptom free for at least another 24 hours. If there are no symptoms with low level of exertion, the patient can increase the level of activity every few days. Any recurrence of symptoms should signal immediate cessation, rwith est for at least 24 hours and resumption of previous symptom-free activity.

For 90% of patients, the symptoms of concussion resolve after 2 weeks. Ongoing symptoms of headache, fatigue, insomnia, dizziness, irritability, mood disturbance, apathy, or personality changes may signal post-concussion syndrome, which requires further evaluation and management by a neurologist or neuropsychologist. Though there are several modalities including tricyclic antidepressants, neuroepinephrine selective reuptake inhibitors, and anti-epileptic agents in use for this syndrome, there are no clinical trials that show superiority of any of these agents. Patients with new onset seizures within one week of the traumatic event should be started on anti-epileptic medications and weaned several weeks after. This is mainly to prevent status epilepticus.

E. Common Pitfalls and Side-Effects of Management

The most important factors in concussion management is evaluating for other serious injuries including intracranial hemorrhage and more serious traumatic brain injury, educating patients about the importance of rest in recovery, and ensuring proper follow-up options for possible complicated recovery.

IV. Management with Co-Morbidities

The evaluation for concussion may be significantly more difficult in a patient who is severely physically handicapped and unable to participate in tests of balance or coordination.

Evaluation of both symptoms and obtaining an accurate mental status examination will also be more difficult in a patient with altered mental status or cognitive or psychiatric impairment at baseline. Though management would center on physical and cognitive rest, there is a lower threshold to perform neuroimaging and have closer observation after initial injury.

A patient with previous concussions requires close observation, increased length of time on cognitive rest, and slower return to activities to decrease delayed recovery, post-concussion syndrome, and second impact syndrome.

A. Renal Insufficiency.

No change in standard management.

B. Liver Insufficiency.

No change in standard management.

C. Systolic and Diastolic Heart Failure

No change in standard management.

D. Coronary Artery Disease or Peripheral Vascular Disease

No change in standard management.

E. Diabetes or other Endocrine issues

No change in standard management.

F. Malignancy

No change in standard management.

G. Immunosuppression (HIV, chronic steroids, etc).

No change in standard management.

H. Primary Lung Disease (COPD, Asthma, ILD)

No change in standard management.

I. Gastrointestinal or Nutrition Issues

No change in standard management.

J. Hematologic or Coagulation Issues

Intracranial hemorrhage must be excluded with any head trauma.

K. Dementia or Psychiatric Illness/Treatment

Evaluation of both symptoms and obtaining an accurate mental status examination will be more difficult in a patient with altered mental status or cognitive or psychiatric impairment at baseline. Though management would center on physical and cognitive rest, there is a lower threshold to perform neuroimaging and have closer observation after initial injury.

V. Transitions of Care

A. Sign-out considerations While Hospitalized.

Repeat complete neurological exam with a decline in neurologic checks completed by nursing staff. If there is any focal neurologic deficits or decline from previously documented exam, obtain neuroimaging and consider neurosurgery consultation.

B. Anticipated Length of Stay.

Concussion can be managed as an outpatient for majority of patients. Twenty-four to forty-eight hour observation may be necessary for patients that had a prolonged loss of consciousness, uncomplicated seizure, or do not have a home and responsible carer to observe patient for 48 hours after discharge. A patient with isolated concussion and negative head CT result is at minimal risk for developing an intracranial lesion and therefore may be safely discharged.

C. When is the Patient Ready for Discharge.

A patient is ready for discharge as soon as symptoms are adequately managed if there are no risk factors that require neuroimaging or if non-contrast head CT is negative.

D. Arranging for Clinic Follow-up

Patients should have all information regarding their concussion given in writing and if possible sent to a primary care provider as well, since memory may be impacted by concussion.

1. When should clinic follow up be arranged and with whom.

All patients should ideally have evaluation of symptoms by a primary care provider or a health care provider who is trained in concussion management two weeks after a traumatic event.

2. What tests should be conducted prior to discharge to enable best clinic first visit.


3. What tests should be ordered as an outpatient prior to, or on the day of, the clinic visit.


E. Placement Considerations.

Concussion alone does not result in disability requiring placement into a facility.

F. Prognosis and Patient Counseling.

Patients with concussion should be instructed to remain on cognitive and physical rest for at least 24 hours or until symptoms are completely resolved prior to increasing their level of activity. Once symptom-free, the patient can increase the level of activity to include low-impact physical exertion not requiring agility or balance. If symptoms recur, activity should be immediately discontinued until symptom free for at least another 24 hours. If there are no symptoms with low level of exertion, the patient can increase the level of activity every few days. Any recurrence of symptoms should signal immediate cessation, with rest for at least 24 hours and resumption of previous symptom-free activity.

Patients can be counseled that in 90% of diagnosed concussions, symptoms resolve within two weeks of injury with rest. The remaining 10% of patients may experience prolonged symptoms, most commonly headache, fatigue, and feeling generally “slowed down.” These symptoms may be part of a post-concussion syndrome which requires further evaluation by a primary care physician or a concussion specialist. Patients with this syndrome and ongoing symptoms of concussion have increased rates of depression at baseline and have an increased rate of depression after a concussion due to disabling effects of ongoing symptoms.

Since balance, cognition, and reaction time can be altered after a concussion, patients should be counseled to avoid driving or operating machinery for at least 24 hours. Instruction should be given on the importance of cognitive and physical rest and stepwise return to activities. There is an increased risk of repeat concussion prior to resolution of concussion symptoms so patients should also be encouraged to avoid at-risk situations as possible.

VI. Patient Safety and Quality Measures

A. Core Indicator Standards and Documentation.

There are no Centers for Medicare and Medicaid Services (CMS) guidelines for concussion management. Detailed documentation of physical and cognitive exam is most valuable to immediate and long-term management.

B. Appropriate Prophylaxis and Other Measures to Prevent Readmission.

Written instructions and information about concussion at time of discharge is a validated tool for safe discharge of a concussed individual. These serve as guidance during the recovery phase of a concussion. The patient should evaluate symptoms daily until resolution and contact a primary care provider in the event of worsening or new symptoms. Slow resumption of activity will decrease likelihood of delayed recovery. Appropriate symptom management may have a role in preventing post-concussion syndrome. A post-concussion evaluation of symptoms at the 2-week visit should enable proper triage for further neurocognitive or neuropsychological testing in any patient with ongoing symptoms.

VII. What's the evidence?

Erickson, JC. "Treatment outcomes of chronic post-traumatic headaches after mild head trauma in US soldiers: an observational study.". Headache. 2011.

Faux, S, Sheedy, J, Delaney, R, Riopelle, R. "Emergency department prediction of post-concussive syndrome following mild traumatic brain injury—an international cross-validation study". Brain Inj. vol. 25. 2011. pp. 14-22.

Jagoda, AS, Bazarian, JJ, Bruns JJ, Jr, Cantrill, SV, Gean, AD, Howard, PK, Ghajar, J, Riggio, S, Wright, DW, Wears, RL, Bakshy, A, Burgess, P, Wald, MM, Whitson, RR. "American College of Emergency PhysiciansCenters for Disease ControlPrevention:Clinical policy: neuroimaging and decision making in adult mild traumatic brain injury in the acute setting". Ann Emerg Med. vol. 52. 2008. pp. 714-48.

Karceski, S. "Concussion.". Neurology. 2011.

Kelly, JP, Rosenberg, JH. "Diagnosis and management of concussion in sports". Neurology. vol. 48. 1997. pp. 575.

McCrea, M. "Standardized mental status testing on the sideline after sport-related concussion.". J Athl Train. vol. 36. 2001. pp. 274-279.

McCrory, P, Meeuwisse, W, Johnston, K. "Consensus statement on concussion in sport, 3rd International Conference on Concussion in Sport, held in Zurich, November 2008". Clin J Sport Med. vol. 19. 2009. pp. 185-200.

Ryan, LM, Warden, DL. "Post concussion syndrome.". Int Rev Psychiatry. vol. 15. 2003. pp. 310-6.

Smits, M, Dippel, DJ, Haan, GG, de Dekker, HM, Vos, PE, Kool, DR, Nederkoorn, PJ, Hofman, PM, Twijnstra, A, Tanghe, HJ, Hunink, MM. "External validation of the Canadian CT Head Rule and the New Orleans Criteria for CT scanning in patients with minor head injury.". JAMA. 2005. pp. 1519-1525.

Williams, DH, Levin, HS, Eisenberg, HM. "Mild head injury classification". Neurosurgery. vol. 27. 1990. pp. 422.

Williams, WH, Potter, S, Ryland, H. "Mild traumatic brain injury and post-concussion syndrome: a neuropsychological perspective.". J Neurol Neurosurg Psychiatry. vol. 81. 2010. pp. 1116-22.

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