Keywords magnetic resonance spectroscopy - diffusion tensor imaging - functional magnetic resonance
imaging - positron emission tomography - amyloid imaging
In recent years, particularly in sports, the issue of concussions has garnered significant
public attention and concern. The media has extensively covered the experiences of
high-profile athletes and aspiring young individuals engaged in a wide range of sports,
from American football to rugby, soccer, ice hockey, skiing/snowboarding, and others.
This growing spotlight has prompted national and international organizations to dedicate
substantial efforts to disseminating comprehensive reviews, guidelines, position statements,
and recommendations regarding sports-related concussions.
The primary focus in sports-related concussion management focused traditionally on
preventing a premature return to contact activities and thus avoiding the risk of
concussion-related complications, such as dangerous subsequent blows to the head and
persistent postconcussion symptoms.[1 ]
[2 ]
[3 ]
[4 ]
[5 ]
[6 ]
[7 ]
[8 ]
[9 ]
[10 ]
[11 ]
[12 ]
[13 ] However, an emerging concern now centers on the potential for cumulative long-term
impairments resulting from recurrent concussions and sub-concussive hits sustained
throughout an athlete's career.[2 ]
[3 ]
[4 ]
[5 ]
[6 ]
[7 ]
[8 ]
[9 ]
[10 ]
[11 ]
[12 ]
[13 ]
[14 ] The multifaceted medical considerations surrounding sports concussions emphasize
the need for a multidisciplinary approach to assess and manage these injuries comprehensively.
Concussions, as a form of mild traumatic brain injury (mTBI), have become a significant
public health concern, with an annual influx of ∼ 200,000 individuals into emergency
departments, as estimated by the Centers for Disease Control and Prevention (CDC).[1 ]
[14 ]
[15 ]
[16 ] Diagnosing and managing concussions present complex challenges, primarily relying
on clinical symptoms, physical examinations, behavioral assessments, and cognitive
deficits. Precise determination of the juncture at which an athlete can safely return
to competitive activities remains a formidable clinical quandary.[1 ]
[14 ]
[17 ]
Traditional neuroimaging, in the form of computed tomography (CT) or magnetic resonance
imaging (MRI), often fails to reveal structural brain injury because concussive events
rarely result in macroscopic anatomical abnormalities.[18 ]
[19 ]
[20 ]
[21 ]
[22 ] As a result, the contemporary management of concussions relies on other objective
and subjective indicators, such as symptomatic checklists, physical examinations,
comparisons with baseline testing, balance assessments, and computerized neuropsychological
testing.[15 ]
[17 ]
[18 ]
[19 ]
[23 ]
[24 ]
[25 ]
[26 ] Furthermore, the quantification of concussion severity is inundated with challenges,
requiring an exploration of advanced diagnostic modalities and methodologies capable
of providing more precise and objective measures to aid in diagnosis and in turn inform
return to play (RTP) decisions.[4 ]
[5 ]
[15 ]
[27 ]
Given the global participation of > 200 million individuals in organized physical
activities, the development of objective diagnostic and management strategies for
concussions is of paramount importance.[28 ] Although tools like the Sport Concussion Assessment Tool have gained wide validation
and adoption in sporting institutions, the limitations of conventional neuroimaging
techniques highlight the need for more advanced diagnostic paradigms.[29 ]
[30 ]
[31 ]
[32 ]
[33 ]
This article explores the role of imaging modalities in the context of concussion
management and their potential impact on RTP decisions. It delves into the intricacies
of concussion diagnosis, the constraints of existing assessment tools, and the emerging
necessity to develop advanced neuroimaging methodologies capable of providing deeper
insights into the pathophysiology and severity of concussive injuries. Ultimately,
we hope to contribute to the ongoing discourse aimed at refining the diagnostic and
management landscape of sports concussions, with the ultimate goal of safeguarding
the welfare of athletes at all levels of competitive play.
Defining Concussion
A sports-related concussion (SRC) is a form of TBI that occurs due to a direct blow
to the head, neck, or body during a sports or exercise activity.[1 ]
[7 ]
[29 ]
[34 ]
[35 ]
[36 ]
[37 ] This blow generates an impulse force transmitted to the brain and initiates a complex
physiologic process.[12 ]
[15 ]
[26 ]
[38 ] The pathophysiologic basis of concussion involves underlying changes in the brain
due to the microtrauma of neuronal cell membranes.[1 ]
[15 ]
[39 ]
[40 ]
[41 ] This microtrauma triggers a cascade of ionic and metabolic events: changes in intracellular
ion concentrations, release of neurotransmitters, mitochondrial dysfunction leading
to reactive oxygen species production, increased glucose utilization, and decreased
blood flow.[42 ]
[43 ]
[44 ]
[45 ] The cascade involves three phases: an initial period characterized by hyperglycolysis,
followed by metabolic depression, culminating in a recovery phase.[42 ]
[43 ]
Deciphering the precise point at which cerebral restitution permits the athlete's
safe return to competitive activity presents a formidable clinical dilemma. Concussion
symptoms can manifest instantly or gradually over minutes to hours following the traumatic
event.[2 ]
[23 ]
[26 ]
[30 ] Symptoms typically resolve within a few days, but in some cases, they can persist
for weeks.[11 ]
[13 ]
[14 ]
[23 ]
[26 ]
[39 ] It is also important to ensure that symptoms are not attributable to other external
factors, such as alcohol, drugs, medications, or additional unrelated injuries.[15 ]
Nonimaging Diagnosis of Concussion
Nonimaging Diagnosis of Concussion
The American Medical Society for Sports Medicine's “Position Statement on Concussions
in Sports” underscores the challenges in diagnosing concussions due to the absence
of validated tests and a reliance on self-reported symptoms that can be nonspecific.[1 ]
[14 ]
[29 ] These symptoms may include headaches, fogginess, dizziness, visual changes, fatigue,
neck pain, sleep changes, and more.[1 ]
[6 ]
[30 ]
[31 ]
[32 ]
[46 ]
[47 ]
[48 ]
[49 ]
Because of the nuances in presentation, thorough preseason physical evaluations and
consideration of factors such as a history of prior concussions or TBIs, preexisting
conditions, learning disorders, attention-deficit hyperactivity disorder, motion sickness,
mood disorders, migraines, and current medications are crucial.[33 ]
[50 ] Some organizations recommend baseline evaluations using tools like SCAT6, Computerized
CogSport, ANAM, CNSVS, and Immediate Post-Concussion Assessment and Cognitive Testing
(ImPACT).[1 ]
[7 ]
[29 ]
[30 ]
[31 ]
[32 ]
[33 ]
[47 ]
[51 ]
Best practices endorsed by the National Collegiate Athletics Association include baseline
assessments of symptom checklists, cognitive function, and balance.[52 ] On the sidelines, athletes should be removed from the game if they exhibit signs
such as loss of consciousness, tonic posturing, gross motor instability, confusion,
amnesia, seizures, a vacant look, or balance and coordination issues.[1 ]
[6 ]
[30 ]
[31 ]
[32 ]
[46 ]
[47 ]
[48 ]
[49 ] If a concussion is suspected, clinicians should conduct a brief history, assess
orientation, memory, concentration, balance, and speech patterns, and perform cervical
spine evaluation with palpation and range of motion checks during the evaluation process.[1 ]
[6 ]
[9 ]
[10 ]
[14 ]
[29 ]
[35 ]
[53 ]
[54 ]
[55 ]
Current Protocol for Return to Play
Current Protocol for Return to Play
The current RTP guidelines for SRCs have evolved significantly based on the latest
research and a heightened awareness of SRC. These guidelines emphasize the importance
of medical oversight and the careful management of athletes to ensure adequate time
for recovery before resuming competitive play.[8 ]
[29 ]
[56 ]
The CDC and the National Federation of State High School Associations Sports Medicine
Advisory Committee recommend a Six-Step Return to Play Progression structured to ensure
athlete health and safety.[53 ]
[56 ] Only after being symptom free and cleared by a health care professional can athletes
progress through the steps.[8 ]
[29 ]
[53 ]
[56 ] The stepwise approach includes increasing physical activity levels, from light aerobic
exercise to full competition, carefully monitoring symptoms and cognitive function
at each stage.[8 ]
[29 ]
[53 ]
[56 ] The process considers individual variability, with athletes moving between stages
at their own pace, and it emphasizes the importance of medical oversight and communication
among all involved parties.[8 ]
[29 ]
[53 ]
[56 ] Each step of the process takes a minimum of 24 hours for a gradual progression.[29 ]
[56 ]
Unlike past practices that advocated for strict physical and cognitive rest, the current
approach emphasized in the most recent “Consensus Statement on Concussion in Sport”
encourages athletes to engage in daily activities including walking immediately after
the injury.[1 ]
[6 ]
[7 ]
[8 ]
[14 ]
[29 ]
[34 ]
[53 ]
[56 ] Light physical activity and prescribed aerobic exercise within specified thresholds
are introduced early in the treatment plan.[29 ]
[56 ] Athlete symptoms, cognitive function, clinical findings, and the judgment of a health
care provider guide progression through these steps.[29 ]
[56 ] Although unrestricted RTP typically occurs within 1 month of injury, individual
characteristics may extend this time frame.[8 ]
[29 ]
[53 ]
[56 ] Overall, the current RTP guidelines emphasize a personalized, multidisciplinary
approach to concussion management that considers both preexisting and postinjury factors
that can impact an athlete's recovery trajectory.[8 ]
[29 ]
[53 ]
[56 ]
Imaging Modalities in Management
Imaging Modalities in Management
The following discussion provides a thorough understanding of the diverse and complex
neuroimaging methods and approaches of neuroimaging techniques for managing and diagnosing
concussions, delving into each imaging modality and discussing its potential contribution
to the intricate decision-making processes associated with the return to sport in
athletes. A detailed evaluation of various neuroimaging modalities has revealed their
promise in augmenting the understanding of the pathophysiologic underpinnings and
severity assessment of concussions, especially in cases where conventional imaging
methods fall short.
The discussion synthesizes the findings and explores the clinical implications of
these modalities, considering their respective strengths, limitations, and evolving
roles in concussion management. But it important to note that many, if not all, of
the imaging modalities discussed here are not currently ready for real-time use in
clinical management. A considerable amount of additional research is necessary to
refine, simplify, and validate these novel techniques.
Magnetic Resonance Imaging
As previously mentioned, routine clinical MRI sequences obtained in patients with
SRC often fail to reveal structural brain injury because concussive events rarely
result in macroscopic structural changes.[18 ]
[19 ]
[20 ]
[21 ]
[22 ] In some cases, mTBI may result in cerebral microhemorrhage that can be detected
on certain MRI sequences due to the paramagnetic properties of blood degradation compounds,
specifically deoxyhemoglobin, ferritin, and hemosiderin.[57 ] Susceptibility weighted imaging (SWI) has been found to be more sensitive for detecting
microbleeds compared with T2*-weighted gradient-echo (GRE) imaging. Some evidence
indicated that traumatic microbleeds predict cognitive outcome and persistent posttraumatic
complaints in patients with mTBI.[58 ] Therefore, when performing routine noncontrast brain MRI in the work-up of patients,
substituting the more commonly performed T2*-weighted GRE sequence with SWI is highly
recommended ([Fig. 1 ]).
Fig. 1 A 45-year-old former football player with a history of multiple prior concussions.
Axial susceptibility weighted imaging minimum intensity projection image reveals a
small focus of susceptibility artifact in the anterior right frontal lobe (arrow),
consistent with prior microhemorrhage. Other routinely obtained magnetic resonance
imaging sequences in this patient revealed no other structural or anatomical abnormality.
Magnetic Resonance Spectroscopy
Proton magnetic resonance spectroscopy (MRS), a noninvasive technique, has displayed
substantial promise by shedding light on neurochemical changes that might remain hidden
when relying solely on conventional MRI for structural assessments. Specifically,
MRS has uncovered crucial alterations in critical metabolites such as N-acetyl aspartate
(NAA), choline (Cho), and creatine-phosphocreatine (Cr) ratios, even when no discernible
structural injury is apparent on standard MRI.[59 ] Studies focusing on SRCs have demonstrated the diminished NAA-to-Cr ratio during
the acute phase of injury that signifies metabolic disturbances.[60 ]
[61 ]
Importantly, these ratios have shown signs of recovery within 30 days postinjury,
underlining the potential of MRS to monitor metabolic changes longitudinally and thus
potential application to RTP decision making. NAA relates to neuronal and axonal integrity.
Altered NAA levels provide insights into neuronal loss, metabolic disruptions, or
myelin repair processes.[62 ]
[63 ] Cho levels, in contrast, tend to increase after head trauma, pointing to dynamic
cell membrane turnover. At the same time, the Cr peak emerges as a reliable indicator
of baseline cellular energy metabolism and serves as a reference peak for calculations
of the NAA-to-Cr ratio and Cho-to-Cr ratios.[64 ]
Despite the wealth of information MRS provides, there is a notable gap in research
on mTBIs both in SRC and non–sports-related forms. Existing studies have predominantly
focused on moderate to severe TBI. Although common trends in MRS studies of mTBI,
both in SRC and non–sports-related incidents, often involve reduced NAA and increased
Cho levels, with Cr levels presumed to be stable, emerging research suggests that
this presumed stability may not hold true.[20 ]
[64 ] In conclusion, using MRS in the context of concussion management and RTP decision
making offers a valuable window into the dynamic metabolic changes occurring in the
brain after injury. Understanding the subtle abnormalities inherent in concussive
injuries is important and emphasizes the need for further research in this area.
Diffusion Tensor Imaging
Diffusion tensor imaging (DTI), an advanced MRI technique that harnesses the directional
analysis of water diffusion within white matter ([Fig. 2 ]), offers a unique window into the brain's microstructural changes following concussions.[20 ]
[21 ]
[22 ]
[65 ]
[66 ]
[67 ] Studies using DTI have mainly centered on nonathletes, providing valuable insights
into the alterations occurring in white matter regions.[21 ]
[22 ] DTI has shown a remarkable ability to detect white matter injuries even when conventional
MRI sequences appear normal, making it a valuable tool for concussion assessment.[20 ]
[21 ]
[22 ]
[65 ] More recently, quantitative DTI, and one key metric in particular, fractional anisotropy
(FA), showed potential for assessing the severity of concussions.[22 ]
[65 ]
[66 ]
[68 ] Reduced FA is correlated with more severe symptoms, even in subjects with structurally
normal imaging.[69 ] Abnormal findings on quantitative DTI correlate with impaired reaction time, emphasizing
its practical relevance in concussion management.[66 ]
Fig. 2 Usage of hybrid diffusion imaging (HYDI) to detect white matter microstructure alterations
in patients with chronic traumatic brain injury (TBI). Tract-based spatial statistics
(TBSS) maps of significant differences of intra-cellular volume fraction (Vic ) between TBI patients and healthy controls. Red-orange voxels indicate regions with
significantly lower Vic values in TBI versus controls, whereas green voxels indicate no significant differences.
Abnormal fiber tract diffusion metrics are useful for detecting long-term alterations
of declining neurite density. Specifically, decreased Vic within the posterior periventricular regions may be disruptive to the overall integrative
of the whole-brain white matter network, which can help explain long-term cognitive
and behavioral symptoms after TBI. Image courtesy of Dr. Andrew B. Newberg.
Despite the potential of DTI, its utility is influenced by various factors, including
the timing of imaging postinjury.[22 ]
[65 ] Studies indicate that the results of DTI can vary as time elapses from the initial
insult.[22 ]
[65 ] Understanding the complex and dynamic nature of brain injuries, particularly SRC,
is vital when interpreting DTI findings. The heterogeneity of results observed in
different studies underscores the importance of considering the time elapsed since
the injury, the age of the patient, and the presence of previous concussions when
analyzing DTI data.
As DTI continues to gain prominence in concussion research, it is essential to address
the need for data collection and analysis standardization. Uniformity in DTI protocols
and data interpretation across different platforms remain critical challenges. The
emergence of other advanced diffusion imaging techniques, such as diffusion spectrum
imaging, hybrid diffusion imaging (HYDI), q-ball imaging, and high angular resolution
diffusion imaging (HARDI), presents new avenues for improving our understanding of
concussions.[70 ]
[71 ] DTI has already made significant contributions to the field, but ongoing research
and advancements in neuroimaging will likely further enhance our ability to assess
and manage concussions effectively.
Functional Magnetic Resonance Imaging
Functional magnetic resonance imaging (fMRI) uses the blood oxygen level-dependent
(BOLD) contrast to provide insights into neuronal activity within the brain ([Fig. 3 ]).[18 ]
[72 ] The BOLD signal in fMRI is sensitive to blood-based properties, particularly the
magnetic susceptibility produced by deoxyhemoglobin.[17 ]
[18 ]
[20 ]
[63 ] The fundamental principle underlying fMRI is that increased neuronal activity in
a specific brain region leads to an elevation in local blood flow, resulting in reduced
deoxyhemoglobin concentrations in nearby vessels.[17 ]
[18 ]
[20 ]
[63 ] The heightened presence of oxyhemoglobin, corresponding to neuronal activity, results
in higher signal intensities, allowing for the indirect assessment of neuronal responses
to cognitive and sensorimotor tasks.[17 ]
[18 ]
[20 ]
[63 ]
Fig. 3 Increased fractional amplitude of low-frequency fluctuations (fALFF) on blood-oxygen-level-dependent
(BOLD) imaging in mild traumatic brain injury (mTBI) patients compared with healthy
controls. Hot colors denote areas of increased fALFF in the mTBI group, including
the circled regions in the right supramarginal gyrus (top row) and the left inferior
parietal region (bottom row). Areas of significantly different resting functional
connectivity reflect increased spontaneous brain activity at rest. Image courtesy
of Dr. Andrew B. Newberg.
Despite its proven efficacy in probing brain function, discussions continue regarding
the clinical utility of fMRI in concussion assessment, especially in the context of
SRC. Studies using fMRI in individuals with mTBI have shown alterations in the BOLD
signal during various cognitive tasks, including working memory, attention, and sensorimotor
functions.[17 ]
[18 ]
[20 ]
[63 ] Task-related fMRI may be a sensitive tool for evaluating residual motor and cognitive
deficits in the subacute phase of mTBI.[27 ]
[63 ]
[72 ]
The prefrontal cortex, particularly the dorsolateral prefrontal cortex (DLPFC), consistently
exhibits increased neural activity in response to cognitive tasks in patients with
postconcussive symptoms.[27 ]
[63 ] This phenomenon, often termed “neural inefficiency,” may be linked to diminished
cognitive performance in SRC patients.[27 ]
[63 ]
[73 ] Recent research delving into spatial memory navigation tasks using fMRI in athletes
with SRC demonstrated distinctive brain activation patterns.[18 ]
[20 ]
[27 ]
[63 ]
[73 ]
[74 ]
[75 ] Although no significant differences in task performance were observed between concussed
individuals and neurologically normal controls, fMRI revealed more extensive cortical
networks with additional activation outside the study's regions of interest.[27 ]
[63 ]
[76 ] The enhanced activation was evident in the parietal cortex, right DLPFC, and right
hippocampus.[17 ]
[27 ]
[63 ]
The bilateral recruitment of the DLPFC in concussed subjects further emphasized the
complexity of neural responses following SRC.[27 ]
[51 ]
[63 ] The increased neural recruitment observed in studies of working memory dysfunction
in SRC can be attributed to three possible explanations: “brain reorganization,” “neural
compensation,” and the “latent support hypothesis.”[20 ]
[27 ]
[77 ]
[78 ] These explanations differ in their interpretations of the permanence and purpose
of additional neural recruitment in response to cognitive challenges. Research findings
in this area have been somewhat controversial, with some studies suggesting hypoactivation
in specific brain regions, particularly the mid-DLPFC, and variations in activation
patterns based on the presence of depression in concussed athletes.[27 ]
[63 ]
[73 ]
[75 ]
Positron Emission Tomography
Positron emission tomography (PET) imaging, with its capability to measure brain metabolism,
has emerged as a powerful neuroimaging technique for assessing metabolic disturbances.[18 ]
[24 ]
[74 ]
[79 ]
[80 ]
[81 ]
[82 ]
[83 ] This technology offers a unique window into the functional alterations in the brain
and holds particular promise for SRCs. Conventional imaging modalities such as MRI
or CT lack the ability to capture the nuanced metabolic changes seen in SRC.[18 ]
[19 ]
[20 ]
[21 ]
[22 ] PET provides a more thorough understanding of the metabolic activity of brain regions
and their correlation with the associated neurovascular changes linked to symptomatology
through the use of radionucleotide tracer fludeoxyglucose F18 (abbreviated as 18F-FDG)
that measures local glucose metabolism in various brain regions.[74 ]
[84 ]
[85 ] PET imaging can be combined with CT or MRI for anatomical localization ([Fig. 4 ] and [Fig. 5 ]).
Fig. 4 Axial attenuation corrected fused FDG PET-MR images of the brain in a 35-year-old
female with history of prior concussions particularly to the front of the head, obtained
for research purposes. In this case, there was decreased metabolism in the left superior
frontal region (blue arrow) along with increased metabolism in the right frontal region.
A common finding in patients with post-concussion syndrome is a mix of areas of increased
and decreased metabolism. These findings correlate with symptoms such as poor concentration
when frontal lobe metabolism is abnormal. Image courtesy of Dr. Andrew B. Newberg.
Fig. 5 Axial PET attenuation corrected (a) and axial fused PET-MR (b) images of the brain
in a 52-year-old female with history of multiple prior concussions, obtained for research
purposes. In this case, there was mildly decreased metabolism in the left inferior
occipital region (arrow) and right fusiform gyrus and superior temporal region (arrowheads).
There was mildly increased metabolism in the left insula (curved arrow), as well as
the hypothalamus, midbrain, left orbital gyrus, right thalamus, and right nucleus
accumbens (not shown). Decreased metabolism in the occipital lobe along with increased
metabolism in the thalamus and temporal regions can be associated with visual processing
problems, including hypersensitivity to light. Abnormal function in the superior temporal
region can also be associated with verbal processing problems. Increased metabolism
in the hypothalamus, nucleus accumbens, insula, and midbrain can be associated with
emotional dysregulation as well as general problems with cognitive processing speed.
Increased metabolism in the orbital regions can be associated with impaired concentration
and cognition. In general, areas of increased metabolic activity are typically associated
with inflammation or a persistent neuroexcitatory state associated with a history
of head injury, and areas of decreased metabolic activity are associated with reduced
neuronal function, most likely from injury.
A recent study compared patients with a single blunt mTBI from a vehicle accident
with age-matched controls. The study revealed a complex pattern of hypermetabolism
in some brain regions (parahippocampal gyrus, middle temporal gyrus, cingulate, precuneus,
and brainstem) and concurrent hypometabolism in others (angular gyrus, calcarine cortex,
and middle/superior frontal brain regions).[84 ] This novel approach highlighted the association between hypometabolism in frontal
brain regions and decreased cognitive scores. These results provided clear evidence
for the sensitivity of 18F-FDG PET in linking changes in glucose metabolism with cognitive
function.[84 ] The lack of specificity of 18F-FDG PET, combined with the complexity of understanding
changes in glucose metabolism, raises questions about its utility as a diagnostic
biomarker for SRC.[24 ]
[84 ]
Tau PET imaging has emerged as a promising avenue of research in this field, especially
for assessing tau pathology in patients with TBI.[76 ]
[79 ]
[80 ]
[83 ]
[84 ] Following a single TBI, of any type, including sports-related concussion, pathologic
findings suggest that a third of subjects exhibit neurofibrillary tangles at autopsy
years after injury.[86 ] Currently, research indicates that axonal injury leads to tau hyperphosphorylation
and aggregation.[79 ]
[83 ] However, the precise mechanisms remain unclear. Recent advancements in tau-selective
radiotracers have provided opportunities to visualize tau pathology in patients with
TBI. The most widely used tau PET tracer, 18F-AV-1451 (18F-flortaucipir), was evaluated
in patients with a single moderate to severe TBI history.[84 ] The findings revealed significant differences in the spatial extent of 18F-flortaucipir
signals in gray and white matter regions compared with age-matched controls, suggesting
distinctive tau deposition patterns in TBI patients.[84 ]
Various radiotracers have provided insights into the dynamics of β-amyloid deposition
within the brain.[87 ]
[88 ]
[89 ] Recent case reports using 18F-florbetapir have demonstrated intriguing patterns
of β-amyloid deposition in the aftermath of TBI.[84 ] Although there is an initial increase, this deposition appears to clear over time
in specific brain regions.[87 ]
[88 ] These findings highlight the complexity of β-amyloid accumulation dynamics following
TBI and emphasize the need for comprehensive investigation.[87 ]
[88 ] If researchers can quantify β-amyloid deposition models, it would be possible to
develop the ability to monitor SRC in cases of subclinical symptomatology. Factors
beyond the occurrence of TBI, such as age, genetic risk, or vascular factors, may
influence β-amyloid deposition and need to be controlled for in future studies and
could hinder potential future applications.[84 ]
[87 ]
[88 ]
In the context of SRC, PET has the potential to provide invaluable insights into the
metabolic and functional alterations in the brain. The challenges of interpreting
these findings within the broader clinical context further emphasize the multifaceted
nature of RTS decision making. As research in this field continues to evolve, PET
remains a promising tool with the potential to enhance our understanding.
Vestibulo-Ocular Dysfunction and Eye Tracking
The prevalence of vestibulo-ocular dysfunction in concussions is evident, with vestibular
and oculomotor symptoms frequently reported.[6 ]
[15 ]
[29 ]
[30 ]
[47 ]
[90 ]
[91 ]
[92 ]
[93 ] Screening using tools like vestibular/ocular motor screening (VOMS) has shown promise
in detecting changes in symptom provocation and components of vestibular function.[29 ]
[91 ]
[93 ] Eye tracking, although challenging to implement on the sidelines, can detect abnormal
ocular motility patterns associated with concussions, necessitating establishing appropriate
error thresholds and optimizing sensitivity and specificity.[30 ]
[47 ]
[91 ]
[92 ]
[93 ] Emerging technology that attempts to track eye movements digitally and produce imaging
reports shows significant promise and will allow further objective assessment of eye
movements that can be combined with reported symptom provocation related to eye-tracking
testing.[93 ]
Chronic Traumatic Encephalopathy
Chronic Traumatic Encephalopathy
Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease linked to repetitive
head impacts.[74 ]
[76 ]
[79 ]
[80 ]
[86 ]
[87 ]
[88 ]
[94 ] CTE, which occurs predominantly in contact sports and military service, presents
a significant challenge because a diagnosis can only be made postmortem at this time.
This limitation prevents intervention and comprehensive patient care.
The emerging role of neuroimaging techniques in the in vivo diagnosis of CTE is a
promising development.[74 ]
[76 ]
[79 ]
[94 ] MRI has revealed significant alterations in brain structure and function among individuals
with CTE including changes in brain volume, ventricular enlargement, cerebral atrophy,
white matter organization, cortical thinning, and functional connectivity.[74 ]
[80 ]
[94 ] These findings are indicative of the neuropathologic changes associated with CTE
and provide a potential tool for early diagnosis and intervention.
MRS has proven to be sensitive in detecting neuroinflammation, neuronal loss, and
axonal injury, all of which are characteristics observed in CTE.[70 ]
[72 ]
[75 ]
, Studies indicate that MRS can correlate neurochemical changes associated with neuroinflammation
with mood symptoms and behavioral changes in former NFL players.[95 ] Advancements in two-dimensional MRS allow more precise measurements of metabolites
and neurotransmitters.[59 ]
[64 ] A further subtype of MRS, localized correlated spectroscopy, allows detection of
different brain metabolites in various brain regions.[96 ]
PET and radionucleotides are promising future methods of diagnosing CTE by detecting
tau aggregates.[79 ]
[83 ] Radionuclide 18F-FDDNP has shown potential in distinguishing CTE from other conditions.[74 ] The limitation of these methods includes financial coverage, nonspecific binding,
and safety concerns.[74 ] In Shin's 2023 review in the National High School Journal of Science, there is a discussion about the need for personalized models of tau-induced atrophy
in CTE, allowing clinicians to understand the trajectory of individual disease processes
and intervene accordingly.[94 ] Diagnosing CTE in living patients remains a significant challenge, but neuroimaging
will likely emerge as the center point of in vivo diagnosis.
Conclusion
The management and RTP decision making in SRCs have evolved significantly over recent
years, driven by increasing public awareness and the multidisciplinary approach adopted
by medical professionals, researchers, and sports organizations. This article illuminated
the multifaceted nature of concussions, emphasizing the significance of various imaging
modalities in enhancing our understanding of these injuries.
The discussion surrounding imaging modalities, including MRS, quantitative DTI, fMRI,
PET, and VOMS, highlighted their potential to offer valuable insights into the pathophysiologic
processes and severity assessment of concussions. These technologies offer a dynamic
and comprehensive perspective on brain function and structure, with each modality
contributing to a more complete understanding of the intricacies of concussions.
Despite the progress made in the field of concussion-related neuroimaging, significant
challenges and gaps in research remain. The need for standardization in data collection
and analysis within the development of advanced imaging techniques, such as tau PET
imaging, are ongoing areas of exploration. Additionally, integrating imaging data
with clinical assessments and neuropsychological tests is crucial for making informed
RTP decisions and monitoring recovery. Thus all of the imaging modalities described
here remain outside the scope of standard practice and are primarily limited to research
applications.
This literature review underscored the evolving landscape of concussion management,
guided by the promise of advanced imaging modalities in elucidating the complex nature
of concussions. As research continues to advance, these tools hold the potential to
improve the accuracy of diagnosis, inform treatment strategies, and ultimately enhance
the welfare of athletes who sustain head trauma. Integrating these imaging techniques
into the broader context of clinical care and RTP decision making would represent
a significant step forward in mitigating the short- and long-term consequences of
SRCs.
