1Graduate Department of Rehabilitation Science, University of Toronto, 2Occupational Science and Occupational Therapy, University of Toronto, 3Department of Psychology, University of Toronto, 4Bloorview Kids Rehab, 5Toronto Rehab, 6Cognitive Neurology, Sunnybrook Health Sciences Centre, 7Faculty of Medicine, University of Toronto
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Keightley, M., Green, S., Reed, N., Agnihotri, S., Wilkinson, A., Lobaugh, N. An Investigation of the Effects of Sports-related Concussion in Youth Using Functional Magnetic Resonance Imaging and the Head Impact Telemetry System. J. Vis. Exp. (47), e2226, doi:10.3791/2226 (2011).
One of the most commonly reported injuries in children who participate in sports is concussion or mild traumatic brain injury (mTBI)1. Children and youth involved in organized sports such as competitive hockey are nearly six times more likely to suffer a severe concussion compared to children involved in other leisure physical activities2. While the most common cognitive sequelae of mTBI appear similar for children and adults, the recovery profile and breadth of consequences in children remains largely unknown2, as does the influence of pre-injury characteristics (e.g. gender) and injury details (e.g. magnitude and direction of impact) on long-term outcomes. Competitive sports, such as hockey, allow the rare opportunity to utilize a pre-post design to obtain pre-injury data before concussion occurs on youth characteristics and functioning and to relate this to outcome following injury. Our primary goals are to refine pediatric concussion diagnosis and management based on research evidence that is specific to children and youth. To do this we use new, multi-modal and integrative approaches that will:
1.Evaluate the immediate effects of head trauma in youth
2.Monitor the resolution of post-concussion symptoms (PCS) and cognitive performance during recovery
3.Utilize new methods to verify brain injury and recovery
To achieve our goals, we have implemented the Head Impact Telemetry (HIT) System. (Simbex; Lebanon, NH, USA). This system equips commercially available Easton S9 hockey helmets (Easton-Bell Sports; Van Nuys, CA, USA) with single-axis accelerometers designed to measure real-time head accelerations during contact sport participation 3 - 5. By using telemetric technology, the magnitude of acceleration and location of all head impacts during sport participation can be objectively detected and recorded. We also use functional magnetic resonance imaging (fMRI) to localize and assess changes in neural activity specifically in the medial temporal and frontal lobes during the performance of cognitive tasks, since those are the cerebral regions most sensitive to concussive head injury 6. Finally, we are acquiring structural imaging data sensitive to damage in brain white matter.
1. Obtaining Pre-injury Neuropsychological Baseline Profile on Subject
2. Acquiring Structural and Functional MRI Baseline Images on Subject
3. Recording the Force and Direction of Hits to the Head using the Head Impact Telemetry (HIT) System
4. Performing Post-mTBI Neuropsychological Follow-up Testing
5. Acquiring Structural and Functional MRI Post-mTBI Follow-up Images
6. Performing Matched Control Subject Neuropsychological Follow-up Testing
7. Acquiring Structural and Functional MRI Matched Control Subject Images
8. Data Analyses
9. Representative Results
Head Impact Telemetry System
Table 3 depicts quantitative data recorded for corresponding impacts illustrated in Figure 2. Peak linear acceleration is the maximum linear acceleration of a player's head during impact. The units are g's. A g is the acceleration of gravity at sea level (9.8 meters per second squared). Peak rotational acceleration is the maximum rotational acceleration of a player's head during impact. The units are radians per second squared. Azimuth is a measure of impact location. Azimuth is defined from -180° to 180° with 0° at the back of the head and positive azimuth to the right side of the head. Elevation is the other measure of impact location. Elevation is defined from 0° (horizontal plane passing through the head center of gravity) to 90° (crown of the head).
Figure 3 depicts serial fMRI results from a) concussed athletes with symptom resolution and b) with no symptom resolution. Note: task-related brain activities in the frontal region are clearly observed only in athletes with symptom resolution.
Figure 1. Schematic diagram of the externally ordered working memory task.
Figure 2. Example of HIT System data interface showing directional vectors indicating the location for the six hits described in Table 3. Simbex 2006.
Figure 3. Serial fMRI results from a) concussed athletes with symptom resolution and b) with no symptom resolution. PCS=post-concussion symptoms; n=number of subjects; ▲BOLD = change in blood oxygenation level dependent signal; DLPC = dorsolateral prefrontal cortex.
|Scan Type||Sequence||TE/TR/TI/FA1||Matrix/ FOV(cm)2||NEX3||Slice Thickness/ # Slices||Other||Scan Time|
|T1 weighted||3D spoiled gradient echo with inversion preparation (SPGR-IRprep)||5.9/1.3/300/20||256 160/22||2||1.4/128||7:30|
|PD/T2 weighted||Dual-echo fast spin echo (FSE)||20,102/2.9s/||256 192/22||2||3/48||interleaved||12:00|
|Diffusion Tensor||Single-shot echo planar imaging, with dual spin echo||min/~9s/||128 128/33||2||2.6/50+||b-value:1000 s/mm2
|T2*||Gradient echo||20/350/ /20||256 192/22||1||3/48||interleaved||4:30|
|fMRI||Single-shot T2*, with spiral in/out readout||30/2s/ /70||64 64/20||5/26||peripheral monitoring: respiration, cardiac||12:00-15:00|
|qT2||Poon & Henkleman||10/2500/||128 128/24||4||4/1||21:00|
Table 1. Details of Scan Parameters For Clinical and Functional MR Sequences at 3T.
1 TE (echo time); TR (repetition time); TI (inversion time); FA (flip angle)
2 FOV (field of view)
3 NEX (number of excitations)
|Time||Post-Concussion Symptom Scale (PCS)||Working
|Baseline Year 1||X||X||X||X||X|
|Post-Concussion (PC) Day 1||X||X||X||X|
|PC Day 2||X|
|PC Day 3-4||X|
|PC Day 5-6||X||X||X||X|
|PC Day 7||X|
|Weekly after Day 7||X|
|Baseline Year 2||X||X||X||X||X|
Table 2. Administration of Neuropsychological Measures for All Subjects.
Note: Each individual concussed subject will be matched with orthopedic and no injury control subjects. The control subjects will be administered the measures for the same time frame as the concussed subject they are matched with. For example, if a concussed subject experienced resolution of PCS symptoms on day 14, an orthopedic control subject as well as a no injury control subject would also be administered the full neuropsychological assessment on day 14 (i.e. treated as though their 'PCS' symptoms resolved on day 14) in order to match data points.
|Event Date||Event Time||Peak Linear Acceleration||Peak Rotational Acceleration||Azimuth||Elevation|
Table 3. Sample of data collected from one player with one helmet.
We predict that those youths who show the greatest impact on brain white matter will show the greatest reorganization of brain activity, and the longest behavioural and neural recovery periods. This research will provide a better understanding of pediatric post-concussion events and have a significant impact on medical care, as it will allow us to establish a recovery protocol based on research evidence that is specific to children and youth. Such a protocol can then be translated to stakeholders, including parents, coaches and doctors. To achieve these goals, we will characterize and quantify further the neuropsychological and neural sequelae in concussed pediatric athletes. We also measure cognitive improvement and changes in brain structure and activity patterns that accompany behavioural recovery. In addition, the study will provide a new look at the impact of concussion and repeated non-concussive head impacts on long-term brain plasticity and development in youth.
No conflicts of interest declared.
We would like to thank the Canadian Institutes of Health Research (CIHR) and the Ontario Neurotrauma Foundation (ONF) who have provided funding for this research.
|AccuGait Portable Gait and Balance Platform (Balance Assessment)||AMTI||www.amti.biz|
|NetForce Balance Data Acquisition Software||AMTI||www.amti.biz|
|Visual Conflict Dome||Fabricated by researchers; modeled after: Lovell MR, Collins MW. Neuropsychological assessment of the college football player. J Head Trauma Rehabil. 1998;13(2):9-26.|
|Airex Balance Pad||Airex||www.bebalanced.net|
|Smedlay’s Dynamometer, 100 kg(Grip Strength)||TTM, Tokyo|
|Grooved Pegboard Test||Lafayette Instruments||www.lafayetteinstrument.com|
|Axon Jump Mat||Vacumed||www.vacumed.com|
|Strength Bar||Fabricated by researchers:
|Head Impact Telemetry (HIT) System||Simbex||www.simbex.com|
|Post-Concussion Symptoms Scale Revised (PCS-R)||Adapted from:
Lovell MR, Collins MW. Neuropsychological assessment of the college football player. J Head Trauma Rehabil. 1998;13(2):9-26.
|GE Discovery MR750 3.0T MRI Scanner||GE Healthcare||www.gehealthcare.com|
|GE 8 channel head coil||GE Healthcare||www.gehealthcare.com|
|Lumitouch Reply System||Lightwave Medical Industries||Vancouver, BC 1-(604)-875-4529|
|Back projection screen (for presenting fMRI stimuli)||Unknown|
|Disposable foam ear plugs||PAR Inc.||www.parinc.com|
|Neuropsychological Tests||Pearson Assessments||www.pearsonassessments.com|