Sunday, January 5, 2014

Concussions in the NHL


According to TSN, there are currently 100 players injured in the NHL across all 30 teams. There are currently 6  players injured due to concussions (with an additional 3 due to post-concussion syndromes), making head injuries a major topic around the hockey world. This is evident by the increased focus on hits to the head by the Department of Player Safety.

Earlier in the season, New York Rangers forward Rick Nash was diagnosed with a concussion and placed on IR after a high hit by San Jose Sharks defenseman Brad Stuart. As shown in the suspension video below, Stuart makes significant head contact by launching himself up into Nash. As the primary point of contact (PPOC) was the head and Nash was injured, Stuart was suspended three games for the hit.

At the time, this wasn't good news for Rangers fans since it wasn't Nash's first concussion. Nash reportedly suffered a concussion after a hit by Lucic just twelve games into last season and missed four games. Nash has since returned and has 16 points in 26 games on the season.

Of the other NHLers sidelined due to a concussion, all were caused due to contact with the head (Update: Backstrom, Josi and Kronwall have returned. This article has been in the process of writing since October so not all are up to date, sorry!).


Also known as a mild traumatic brain injury, the concussion is the most common type of traumatic brain injury. At the 4th International Conference on Concussion in Sport (Zurich, November 2012), a panel discussion took place to obtain a consensus-based definition of a concussion. The Concussion in Sport Group (CISG) defined a concussion as follows:
Concussion is a brain injury and is defined as a complex pathophysiological process affecting the brain, induced by biomechanical forces. Several common features that incorporate clinical, pathologic and biomechanical injury constructs that may be utilised in defining the nature of a concussive head injury include: 
  1. Concussion may be caused either by a direct blow to the head, face, beck or elsewhere on the body with an "impulsive" force transmitted to the head.
  2. Concussion typically results in the rapid onset of short-lived impairment of neurological function that resolves spontaneously. However, in some cases, symptoms and signs may evolve over a number of minutes to hours.
  3. Concussion may result in neuropathological changes but the acute clinical symptoms  largely reflect a functional disturbance rather than a structural injury and, as such, no abnormality is seen on standard structural neuroimaging studies.
  4. Concussion results in a graded set of clinical symptoms that may or may not involve loss of consciousness. Resolution of the clinical and cognitive symptoms typically follows a sequential course. However, it is important to note that in some cases symptoms may be prolonged.  
Boy, that's a pretty long definition. In essence, a concussion is a head injury with a temporary loss of brain function that may result in a variety of physical, cognitive, and emotional symptoms.


Concussion is considered to be among the most complex injuries to diagnose in sports medicine. The majority of concussions in sport occur without a loss of consciousness or frank neurological signs and the symptoms can be difficult to recognize (McCrory et al.). The aforementioned Zurich 2012 consensus panel agreed that concussion "is an evolving injury in the acute phase with rapidly changing clinical signs and symptoms, which may reflect underlying physiological injury in the brain." Additionally, there is no perfect diagnostic test that physicians can rely on for an immediate diagnosis of  a concussion, especially in a sporting environment. Most concussions also cannot be identified or diagnosed by advanced neuroimaging techniques, such as a CT scan or MRI, unlike other neurological injuries/diseases.

Right now, a concussion is a clinical diagnosis based largely on the observed injury mechanism (point of contact, force on head area, etc.), signs, and symptoms. The first step towards a diagnosis of a concussion is actual recognition of the injury. As always in the NHL, a huge hit will garner the most attention, however it's important for team trainers, coaches, and physicians to be vigilant of smaller hits or multiple hits in a short period of time. The combined effects of multiple hits over a short period of time may be worse than just one large hit. This is largely due to the unknown mechanism of the injury. For example, a recent study evaluated the relationship between the force of impact and clinical outcome, finding that magnitude of impact did not correlate with clinical injury (Guskiewicz et al.). The study showed that despite the fact that the impact magnitude of the hits sustained by concussed athletes ranged from 60.51 to 168.71 g (!), no significant relationships between those impacts and symptom severity/neurocognitive functioning were found.

Sport-related concussions are very difficult to diagnose. This is especially true when the injury is 'mild' or when the symptoms or subtle or masked by the athlete. It's quite common for athletes (at all levels) to assume that "having your bell rung" is part of the game, and don't recognize the significance or consequences of playing with concussions. A study of high-school football players, only 47.3% of players with a concussion reported their injury (of the cohort that didn't report, 66.4% didn't think their injury was serious enough, 41% didn't want to be held out of play) (McCrory et al.).

The symptoms of a concussion are just one component of making a diagnosis, but important to note. The hallmark signs of acute sports concussion include:

  • Loss of consciousness (LOC)
  • Problems with attentional mechanisms
    • Manifested as (but not limited to): slowness to answer questions and follow directions, easily distracted, poor concentration, vacant stare/glassy eyed. 
  • Memory disturbance
  • Balance disturbance
Over the course of the first 24 hours following a concussion injury, other signs and symptoms may manifest. However, it's important to note that there is a large range of these symptoms and they often vary, not all of these symptoms are seen in every case of sports concussion. The most common symptoms reported in concussion literature include:
  • Somatic symptoms such as headache
  • Cognitive symptoms such as feeling like in a fog
  • Emotional symptoms such as lability
  • Physical symptoms such as LOC and amnesia
  • Behavior changes such as irritability
  • Cognitive impairment
  • Sleep disturbance (insomnia)
  • Dizziness and balance problems
  • Blurred vision
  • Fatigue

If any one or more of these symptoms is recognized, a concussion should be suspected and a management plan should be implemented.

Since concussions are often hard to recognize and to diagnose, the McCrory et al study as well as the Zurich Consensus on Concussion in Sport proposed diagnostic criteria for sideline evaluation:
An athlete shows any of the following, they need to be removed from play and assessed.

  • Initial obvious physical signs consistent with concussion (LOC, balance problems)
  • Teammates, trainers, coaches observe cognitive or behavior changes in functioning consistent with concussion symptoms reported
  • Any concussion symptoms reported by the athlete injured
  • Abnormal neurocognitive or balance examination
Following a removal from play:
  • Physician evaluated the player using standard emergency management principles, most notably to exclude  severe head trauma or cervical spine injury
  • Once first aid issues are addressed, assessment of the concussive injury should be made using the SCAT3 or other sideline assessment tools (NHL uses ImPACT concussion testing, read here:
  • The player should not be left alone following the injury and serial monitoring for deterioration is essential over the initial few hours following injury (as seen on 24/7, Abdelkader was driven home by his parents following several hours of testing at Joe Louis arena)
  • A player with diagnosed concussion should not be allowed to return to play on the same day. 
    • It has been unanimously agreed that an athlete should not return to play on the same day of the injury. Studies have shown that athletes allowed back into play following a concussion may demonstrate neuropsychological deficits post injury. 

The SCAT3 is a standardized tool for evaluating injured athletes for concussion and can be used in athletes aged from 13 years and older.


As stated in the International Conference on Concussion in Sport, the consensus panel agreed that the "cornerstone of concussion management is physical and cognitive rest until the acute symptoms resolve and then a graded program of exertion prior to medical clearance and a return to play."

However, current research related to advances in the management of sport concussion is sparse. There is not much evidence for concussion therapies, including how much rest is optimal, different physiotherapy treatments, etc. There is a need for studies which evaluate the effects of a resting period, pharmacological interventions (many doctors will prescribe pain medications as well as anti-inflammatory medications), rehabilitative techniques and exercise (low-levels) for players who have sustained a concussion. 

The graduated return to play protocol following a concussion is a stepwise process and is outline below: 

In this stepwise progression, an athlete only proceeds to the next level if they are asymptomatic at the current level. Each step should take at least 24 hours, making the minimum amount of time to proceed through the full rehabilitation protocol one full week. Athletes should never return to play on the same day as an injury.

Persistent symptoms (>10 days) are reported in 10-15% of all concussions but may be higher in populations such as hockey players and younger aged athletes. Each case should be managed effectively and not rushed.

One thing to consider, especially in the case of NHL concussions, is the role of pharmacological therapy. Drugs may be applied to managing a concussion in two different ways. The first is managing specific or prolonged symptoms such as anxiety, insomnia or sleep disturbance, and post-concussive headaches. The second is using pharmacological therapy as a way to modify the underlying pathophysiology of the condition, with the aim of shortening the duration of concussive symptoms. However, this approach is still only used by experts and involves drugs such as anti-inflammatory medication.
One of the most important considerations in the management of a concussed athlete, is that not only should they be symptom-free, but they need to be symptom-free when off of their pharmacological therapies, so that they don't mask or modify the symptoms.

Management of a concussion is different in each case. Some studies now believe that concussion/TBI is a disease process, rather than an isolated self-limited event (Masel and DeWitt) with post-concussive symptoms, especially post-traumatic headaches reflecting persistent, potentially progressive brain dysfunction.


A few of the most covered topics regarding concussion in the media right now is the phenomenon known as chronic traumatic encephalopathy (CTE). There is a growing awareness that repetitive minor TBIs may lead to persistent cognitive, behavioral, and psychiatric problems and, rarely, to the development of CTE, a progressive degenerative disease which can only be definitively diagnosed postmortem. CTE results in a degeneration of the brain tissue an an accumulation of tau protein. Media outlets report that CTE may show symptoms of dementia (memory loss, aggression, confusion, depression) years after the initial trauma.

However, while clinicians need to be mindful of the potential for long-term problems while managing their athletes, several studies disagree with the media hype of CTE. First and foremost, the International Consensus agreed that CTE represents a distinct tauopathy with an unknown incidence in athletic populations. There has yet to be a proven cause and effect relationship demonstrated between CTE and concussions or exposure to head trauma in sports. CTE has yet to be related to concussions alone and at present, there are no published epidemiological, cohort or prospective studies relating to CTE. The speculation surrounding concussion exposure to CTE is unproven but doctors still need to proceed cautiously and address the fears of parents/athletes from media pressure related to the possibility of CTE.

When meeting with a premiere neuropsychiatrist, he explained to me that there is an absurd amount of hype and lies in some of the articles dealing with CTE. Essentially, no brain that has been autopsied, screened, and diagnosed with CTE has actually been a good brain to diagnose or relate solely to concussions. For example. every single brain that has been diagnosed in the media studies you may have read about is one of a person with distinct underlying neurological problems, or has taken a large load of medications (thinking of Boogard who died of an accidental drug and alcohol overdose). The extent to which age-related changes, psychiatric or mental health illness, alcohol/drug use or co-existing medical or dementing illnesses contributed to the process is unaccounted for in the published CTE literature. The sample size (hey advanced stats guys) of brains diagnosed with CTE is so small and more good brains need to be autopsied and compared. Additionally, the doctor said that second-impact syndrome is a complete myth, but more research needs to be done.


Hopefully this clears things up with NHL fans regarding concussions. They are a serious issue in the game today, and there is serious effort by the NHL to invest in new research.

If you have any questions, please let me know! Hopefully I will be writing more concussion-themed articles soon!


Masel BE, DeWitt DS. Traumatic brain injury: A disease process, not an event. J Neurotrauma. 2010;27:1529-1540. 

McCrory P, et al. Br J Sports Med 2013;47:250-258.

McCrory P, et al. Br J Sports Med 2013;47:268-271.

Guskiewicz KM, Mihalik JP, Shankar V, et al. Measurement of head impacts in collegiate football players: relationship between head impact biomechanics and acute clinical outcome after concussion. Neurosurgery 2007;61:1244–52.