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Current State of Concussion Research
What is a concussion? • A complex pathophysiological process affecXng the brain, induced by traumaXc biomechanical forces
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
Brain injury: a major public health concern
50,000 Deaths
– 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)
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)
235,000 HospitalizaXons
• CDC states TBI (specifically its preven5on) must con5nue to be a na5onal priority
1,111,000 Emergency Department Visits ??? Receiving Other Medical Care or No Care (Langlois et al. 2004: CDC/NCIPC)
“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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Can mouthguards prevent concussion?
Can mouthguards prevent concussion? • 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)
• 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
Postural stability
Mechanism of injury
Concussion history
CogniXon
Mechanism of injury
• Accelerometer research • Football • Ice hockey
Physical exam
TraumaXc Brain Injury
Injury prevenXon
Symptomatology
• AnXcipaXon • InfracXons
Historical biomechanics research
What kinds of impacts cause concussion?
• 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 Mechanism of injury
(Holbourn, 1943 & 1945)
Mechanism of injury
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Historical biomechanics research • Ommaya & Gennarelli (1974):
Recent contemporary work • NFL Concussion CommiZee:
– 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
– 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
• 1 never awoke • 2 others died within 1 hour of the impact Mechanism of injury
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
HIT System • Data are date-‐ and Xme-‐stamped • TransmiZed to Sideline Response System • Measures: – Impact severity – LocaXon of impact
Mechanism of injury
Mechanism of injury
Impact Data • 31 total impacts for both sessions • Between 2.87 g to 97.97 g (mean = 28.95 g)
Mechanism of injury
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Leading with the head: Is it sXll a problem?
• Helmets-‐only pracXce > games • Top of helmet impacts > all other areas
Mechanism of injury
• 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
Neurosurgery, 2007
• Impacts exceeding theoreXcal thresholds did not result in deficits on clinical measures
Mechanism of injury
• No relaXonship between severity of head impact and acute clinical outcomes
Mechanism of injury
Neurosurgery, 2007
Neurosurgery, 2007
Case #
Player Position*
1 2
Mechanism of injury
Linear Magnitude (g)
Rotational acceleration (rad/s2)
Impact Location
ΔSymptom Scores†
ΔSOT Composite‡
OL
60.31
5419.18
Front
2
-4.88
ΔANAM Composite‡
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
4.11
0.49
DB
85.10
3274.05
Top
8
LB
94.20
7665.10
Front
9
DL
99.74
8994.40
Front
4
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 -0.76
No baseline data available 27
-4.07
0.14
12
OL
107.07
2811.45
Top
9
-20.57
13§5
RB
108.02
6711.00
Front
2
-17.79
14
DB
109.88
6632.77
Top
16
2.70
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
-0.06
Mechanism of injury
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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
• Impacts same as college football players • Top of head hits problemaXc in youth hockey
• 4x more impacts in games (~2700 vs. ~650) • Further quesXon proposed injury thresholds (Pellman et al., 2003)
Mechanism of injury
Mechanism of injury
JSET, 2008
Injury prevenXon: AnXcipaXon
Injury prevenXon: AnXcipaXon
• AnXcipated collisions < unanXcipated collisions • ImplicaXons for collision sports Injury prevenXon
Injury prevenXon
Pediatrics, 2010 (In Press)
Teaching AnXcipaXon
Injury prevenXon: InfracXon
• Coaching techniques – PracXce: game-‐related contact drills • Small games drills
Checking from behind
Injury prevenXon
Elbowing/head contact
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Head impact biomechanics
• Elbowing, head contact, high sXcking > legal • Coaches, players, and officials share a responsibility for injury prevenXon
• • • • •
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
Injury prevenXon
MSSE, 2010 (In Press)
“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
“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
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, comprehensionchecking
Fatigue
Decreased arousal/ activation to engage basic attention, working memory
Memory Consolidation/ Retrieval
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
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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Balance Error Scoring System in Virtual Reality
Virtual Reality
Mihalik et al. J Sport Rehab -‐ 2008
Does the weight of the HMD affect balance? – Main finding: it does not
Virtual Reality and RehabilitaXon
(Mihalik et al., J Sport Rehab -‐ 2008)
Virtual reality and rehabilitaXon • AffiliaXons with EA Sports • Nintendo WiiFit – ImplemenXng postural control as a part of a compliant dual task paradigm
Injury rehabilitaXon
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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: jmihalik@email.unc.edu Office: 919.843.2014 Lab: 919.962.0409 Fax: 919.962.0489
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