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Current State of Concussion Research
Jason P. Mihalik, PhD, CAT(C), ATC Assistant Professor
Department of Exercise and Sport Science The University of North Carolina at Chapel Hill
7th Annual Sports Related Conference on Concussion & Spine Injury
Friday, May 14, 2010 Fenway Park, Boston, MA
What is a concussion?
• A complex pathophysiological process affecXng the brain, induced by traumaXc biomechanical forces – Direct blow or impulsive forces transmiZed to head – Typically results in rapid onset of neurological impairments
– Concussion is a funcXonal—not structural—injury – May or may not include LOC – Not idenXfiable on standard imaging (CT, MRI)
(CIS Guidelines, 2009)
Brain injury: a major public health concern
50,000 Deaths
235,000 HospitalizaXons
1,111,000 Emergency Department Visits
??? Receiving Other Medical Care or No Care
(Langlois et al. 2004: CDC/NCIPC)
Costs associated with TBI
• 1.6 to 3.8 million TBI result from sports each year (Langlois et al., 2006 – JHTR)
• $56.3 billion in direct and indirect costs (Langlois et al., 2004 – CDC)
• CDC states TBI (specifically its preven5on) must con5nue to be a na5onal priority
“I thought mouthguards were designed to prevent concussion” Can mouthguards prevent concussion?
• Does wearing a mouthguard affect incidence of concussion? – No significant relaXonship between wearing a MG and incidence of
concussion in games or pracXces; type of MG also did not play a role (Momsen et al. UNC Thesis-‐2004)
• How effecXve is “brain pad” mouthguard? – Random clinical trial comparing WIPSS Brain Pad to mouthguard of
choice
– Result: no difference in number of concussions between Brain Pad MG and MG of choice (Barbic et al. CJSM-‐2005)
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• Custom vs. non-‐custom mouthguards? – No associaXon between mouthguard type and number of concussions in all games and pracXces (Wisniewski et al. Dent Traumatol-‐2004)
• Does wearing a mouthguard reduce the neurocogniXve deficits that follow concussion? – 180 student-‐athletes were assessed following MTBI – Use of mouthguard does liZle to reduce the acute severity of neurocogniXve dysfuncXon and onset of symptoms following sports-‐related head trauma (Mihalik et al. Dent Traumatol-‐2006)
Can mouthguards prevent concussion? Can mouthguards prevent concussion?
• A lack of evidence for mouthguard use prevenXng concussion (Knapik et al. Sports Med-‐2007)
• Do these findings make sense clinically? Biomechanically?
• Mouthguards are effecXve in reducing maxillofacial and dental trauma and should be worn for that reason
TBI: A mulXfaceted condiXon
TraumaXc Brain Injury
CogniXon
Concussion history
Postural stability Mechanism of injury
Physical exam
Symptomatology
Mechanism of injury
• Accelerometer research • Football • Ice hockey
Injury prevenXon
• AnXcipaXon • InfracXons
What kinds of impacts cause concussion?
Mechanism of injury
Historical biomechanics research
• Used animal models: cats, dogs, and monkeys – Pre-‐1940, impacts imparted to fixed heads – 1940s marked pendulum hammers and suspended subjects (Denny-‐Brown & Russell, 1941)
– High-‐speed cinephotography (Pudenz & Shelden, 1946)
• Physical model: wax skull/gelaXnous brain – Developed to eliminate need for animal model – IniXal descripXon rotaXonal acceleraXon was likely needed to produce corXcal lesions and concussion (Holbourn, 1943 & 1945)
Mechanism of injury
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Historical biomechanics research
• Ommaya & Gennarelli (1974): – Ooen credited for rotaXonal acceleraXon – Important addiXon: direct head impacts not needed
– No injuries resulted from linear impacts – 2-‐12 min LOC in 13 monkeys rotaXonal MOI
• 1 never awoke • 2 others died within 1 hour of the impact
Mechanism of injury
Recent contemporary work
• NFL Concussion CommiZee: – Laboratory reconstrucXon of concussive injuries captured on video (Pellman et al. 2003)
• Limited number of cases reconstructed (31/182)
• Injuries likely to occur if lin acc exceeds 70-‐75 g
Mechanism of injury
HIT System • Helmets fiZed with six single-‐axis accelerometers, baZery pack, and telemetry unit
• Spring-‐loaded ensuring contact with head • Data collected at 1 kHz over 40 ms
Mechanism of injury
HIT System
• Data are date-‐ and Xme-‐stamped
• TransmiZed to Sideline
Response System
• Measures: – Impact severity – LocaXon of impact
Mechanism of injury
• 31 total impacts for both sessions • Between 2.87 g to 97.97 g (mean = 28.95 g)
Impact Data
Mechanism of injury
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• Helmets-‐only pracXce > games • Top of helmet impacts > all other areas
Mechanism of injury
Neurosurgery, 2007
Leading with the head: Is it sXll a problem?
• In short: yes • 20% of all impacts occurred to top of head • Our data suggest that players were more likely to sustain an impact of >80 g to top of the head than: – Right side (8.5X) – Leo side (6.54X) – Front (7.08X) – Back (2.43X)
Mechanism of injury
• Impacts exceeding theoreXcal thresholds did not result in deficits on clinical measures
Mechanism of injury
Neurosurgery, 2007
• No relaXonship between severity of head impact and acute clinical outcomes
Mechanism of injury
Neurosurgery, 2007
Mechanism of injury
Case # Player
Position* Linear Magnitude (g)
Rotational acceleration
(rad/s2)
Impact Location
ΔSymptom Scores†
ΔSOT Composite‡
ΔANAM Composite‡
1 OL 60.31 5419.18 Front 2 -4.88
2 RB 60.51 163.35 Top 12 -19.15 -0.20
3 LB 63.84 5923.27 Front 8 -15.68 -0.35
4 WR 66.36 5573.42 Front 23 3.85
5 RB 77.68 3637.48 Top 8 -29.18 0.22
6 DB 84.07 5299.57 Front 7 -2.25 -0.26
7 DB 85.10 3274.05 Top 4 4.11 0.49
8 LB 94.20 7665.10 Front No baseline data available
9 DL 99.74 8994.40 Front 27 -4.07 0.14
10 OL 100.36 1085.26 Top 0 -2.00 1.01
11§3 LB 102.39 6837.62 Right 30 -60.01 -1.56
12 OL 107.07 2811.45 Top 9 -20.57 -0.76
13§5 RB 108.02 6711.00 Front 2 -17.79
14 DB 109.88 6632.77 Top 16 2.70 -0.06
15§14 DB 115.50 2303.63 Top 2 -1.49
16 DL 119.23 7974.22 Right 12 2.89 0.12
17 LB 157.50 1020.00 Front 14 0.71 0.42
18 WR 168.71 15397.07 Back 13 7.33 0.79
19 RB 173.22 4762.74 Top 32 8.08
Mechanism of injury
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• Impacts same as college football players • Top of head hits problemaXc in youth hockey
Mechanism of injury
JSET, 2008
ImplicaXons to youth athleXcs
• Youth ice hockey players sustain impacts similar to Division I football players – 20 to 23 g, depending on posiXon (Mihalik, Guskiewicz, et al.,
2007) – Of great concern: smaller size and younger age
• 4x more impacts in games (~2700 vs. ~650)
• Further quesXon proposed injury thresholds (Pellman et al., 2003)
Mechanism of injury
Injury prevenXon: AnXcipaXon
Injury prevenXon
Injury prevenXon: AnXcipaXon
• AnXcipated collisions < unanXcipated collisions • ImplicaXons for collision sports
Injury prevenXon
Pediatrics, 2010 (In Press)
Teaching AnXcipaXon
• Coaching techniques – PracXce: game-‐related contact drills
• Small games drills
Injury prevenXon: InfracXon
Checking from behind
Elbowing/head contact Injury prevenXon
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• Elbowing, head contact, high sXcking > legal
• Coaches, players, and officials share a responsibility for injury prevenXon
Injury prevenXon
MSSE, 2010 (In Press)
Head impact biomechanics
• Effect of special teams vs. offense and defense • Cervical muscle strength • Player aggression • ConXnued descripXve exploraXon • ConXnued injury study
• Inclusion of different populaXons: – Female, lacrosse, military – Neuroimaging at all levels
“Should my child rest or go to school?”
• 95 concussed student athletes categorized into 5 groups: – No school or exercise acXvity – School acXvity only – School acXvity and light acXvity at home (i.e. mowing lawn, slow jogging)
– School and sports pracXce – School and sports game
• Neuropsychological tesXng and symptom status were analyzed
Rest or no rest?
• Highest level of acXvity following concussion resulted in worse outcomes
• Intermediate levels of acXvity had the best outcomes (But also likely the least severely injured)
• Absolute rest resulted in worse outcomes than intermediate levels of ac5vity
(Majerske, Mihalik et al. JAT-‐2008)
• Is there a potenXal for Xmed exerXon or rehabilitaXon strategies? Area for future research
“Should my child go to school?” Managing FuncXonal Academic Deficits
Neuropsychological Deficit
Functional School Problem Management Strategy
Short focus on lecture, classwork, homework
“Working” Memory Holding instructions in mind, reading comprehension, math calculation, writing
Repetition, written instructions, use of calculator, short reading passages
Memory Consolidation/ Retrieval
Retaining new information, accessing learned info when needed
Smaller chunks to learn, recognition cues
Processing Speed Keep pace with work demand, process verbal information effectively
Extended time, slow down verbal info, comprehension-checking
Fatigue Decreased arousal/ activation to engage basic attention, working memory
Can we use technology to assess and rehabilitate concussion?
• Theory: virtual reality environments provide a mechanism to sXmulate, but not endanger, athletes with concussion
• Different types of VR exist – Cave AutomaXc Virtual Environment (CAVE)
– Head-‐mount display* – Stereo projecXon
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Virtual Reality Balance Error Scoring System
in Virtual Reality
Mihalik et al. J Sport Rehab -‐ 2008
Does the weight of the HMD affect balance? – Main finding: it does not
(Mihalik et al., J Sport Rehab -‐ 2008)
Virtual Reality and RehabilitaXon
Injury rehabilitaXon
Virtual reality and rehabilitaXon
• AffiliaXons with EA Sports
• Nintendo WiiFit – ImplemenXng postural control as a part of a compliant dual task paradigm
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What is to come
• EducaXon • EducaXon • EducaXon
– Coaching iniXaXves – Parental educaXon – Player development – Official educaXonals intervenXons – Physician awareness – CAT(C)/ATC training
Concluding thoughts…
• Clinicians must conXnue to ask quesXons • Researchers must strive to answer RQs
• There is sXll much unknown about concussion
• Concussion management is not an auto-‐pilot funcXon
• Litmus tests to detect injury do not exist
Acknowledgments
Jason P. Mihalik, PhD, CAT(C), ATC Matthew A. Gfeller Sport-Related Traumatic Brain Injury Research Center The University of North Carolina
E-mail: [email protected] Office: 919.843.2014 Lab: 919.962.0409 Fax: 919.962.0489