Mild Traumatic Brain Injury and Concussion

Christopher Reverte

George Kramer

Andy S. Jagoda

THE CLINICAL CHALLENGE

Mild traumatic brain injury (mTBI) including concussion is the most common type of brain injury and can have long-term medical, behavioral, and financial effects on the life of the patient. Of all types of trauma, it may be the most underreported and underdiagnosed because the effect on the patient may not be immediate or clinically overt.

The Glasgow Coma Scale (GCS) was developed as a tool to describe level of consciousness after a traumatic brain injury (TBI) and to assist in prognosis (Figure 11.1). A score of 3 to 8, indicating a severe injury, is associated with coma; a score of 9 to 12, indicating a moderate injury, is associated with lethargy; and a score of 13 to 15, indicating a “mild” injury, is associated with an alert level of consciousness. GCS scores may change over time; and, therefore, a single score is not prognostic, whereas the score at 4 to 6 hours post the injury has a stronger correlation with outcome. Limitations of the GCS score are pronounced in the “mild” range, where 10% to 20% of patients will have a traumatic lesion on head computed tomography (CT), and approximately 1% will have a lesion requiring neurosurgical intervention. Unfortunately, the GCS score is one-dimensional, and when used alone is not a good predictor of injuries in patients.

Concussion is a subcategory of mTBI. A concussion results from direct or indirect biomechanical forces to the brain, resulting in a transient change in brain function. The external forces that lead to concussion may be from a direct impact, a rapid deceleration, a blast injury, or a pressure wave. The transient change in brain function may range from a loss of consciousness (LOC) to pre- and/or post-traumatic amnesia, to more subtle findings including feeling dazed or “foggy,” loss of attention, or decreased reaction time. Patients may experience a brief impact seizure or have an episode of nausea and vomiting. By definition, if a head CT is performed in a patient with a concussion, the finding will be negative for acute intracranial bleeding or other traumatic pathology.

In that mTBIs are heterogeneous, clinical presentations and time course are highly variable. Risk stratification tools such as the New Orleans Head Injury Criteria¹ or the Canadian Head CT Rule² focus on identifying patients with lesions requiring neurosurgical interventions and provide limited value on the clinical course. These tools, however, are helpful in directing the diagnosis
of a patient with an mTBI toward a diagnosis of a concussion. Currently, there is no universally accepted gold standard to confirm the diagnosis of concussion, for example, imaging, a biomarker, or neuropsychological test, although this is an area of intense research. Patients with a concussion may have a wide range of subjective symptoms such as headache, nausea, or fatigue, but these are neither sensitive nor specific for the diagnosis.

Figure 11.1: Glasgow Coma Scale (GCS), total score 3 to 15.

EPIDEMIOLOGY

In the United States alone, it is estimated that there are over 2.5 million cases of TBI treated in the emergency department (ED) annually, with most of those being classified as mild.³ It is difficult to know the true incidence because many TBIs do not present for medical evaluation. Many symptoms are underreported, and many patients may underestimate the importance of their symptoms. Patients often seek medical evaluation when they sustain LOC, but may minimize the importance of less dramatic signs and symptoms; in fact, most patients who sustain a concussion do not have LOC. In general, children and young adults have the highest incidence of concussion.

Civilian injuries may be grouped into sports-related concussions (SRCs) and accidental and non-accidental trauma (Table 11.1). Sports commonly associated with TBIs include football, boxing, basketball, soccer, lacrosse, and hockey. It is estimated by the U.S. Centers for Disease Control and Prevention (CDC) that up to 15% of all contact sport, high school athletes suffer a concussion during a season.⁴ Common accidental causes in young adults and children include falls and bicycle accidents. Elderly patients with limited mobility are at a higher risk of accidental falls. Car crashes and assaults are often associated with alcohol and substance intoxication. TBIs in the military are most commonly caused by a blast injury, often from an improvised explosive device (IED).

Concussions associated with sports have recently been identified as a major public health concern, particularly with football, leading to increased awareness and research in the field. Recent studies estimate the average college football player experiences 800 to 1000 hits to the head in a single season.⁵^,⁶ Although most patients with SRC will have a spontaneous resolution of symptoms, there exists a subset who experience at least one neurobehavioral symptom for up to 3 months after injury, most commonly a headache. Symptoms that persist longer than expected may be part of a post-concussive syndrome (PCS) that may require a multidisciplinary treatment strategy. There is some evidence suggesting that repeat concussions may result in chronic traumatic encephalopathy (CTE) and permanent neurocognitive damage.

TABLE 11.1 Common Injuries Associated with Head Injury

Patient Type	Activity
Civilian	Sports Football, hockey, soccer, lacrosse
	Accidental trauma Falls Bicycle and skateboard accidents Motor vehicle accidents
	Non-accidental trauma Assault with blunt trauma
Military	Blast injury

PATHOPHYSIOLOGY

Direct or indirect forces on the brain result in transmitted energies that create shearing forces on axons; these forces lead to subsequent injury and edema, with consequent neuronal and or axonal metabolic and cellular damage. Although there may be initial structural damage, the prevailing belief is that some amount of functional disturbance is caused by a combination of inflammatory cascades, disrupted neurotransmitters, abnormal cerebral blood flow, and metabolic mismatch. It is likely that there are some feedback loops contributing to subsequent damage and contributing to the development of post-concussive symptoms. The literature suggests a similar, but milder, form of a diffuse axonal injury due to axonal stretching. Distortion to the vasculature, abnormalities with glucose uptake and blood flow, and release of inflammatory mediators have also been implicated. This can cause tearing of neuronal connections and slow the transmission of information that may result in deficits in attention and reaction times, which are hallmarks of a concussion.

There is a growing interest in the role of an inflammatory process associated with a concussion. Following an injury, neutrophils and monocytes secrete inflammatory cytokines as part of an immunologic response. Proinflammatory molecules such as interleukin and tumor necrosis factor-alpha (TNF-α) are thought to be released, contributing to recovery after injury. A better understanding of this inflammatory process could lead to improved diagnostic, prognostic, and treatment modalities.

PREHOSPITAL CONCERNS

In patients suffering from head trauma, other traumatic injuries, including cervical spine injury, should be considered. The basic principles of first aid should still be followed. Patients with TBI who are alert in the field, that is, GCS > 12, are still at risk for deterioration, as classically seen with an epidural hematoma. Patients with a TBI are at high risk for vomiting, and therefore accommodation for emesis should be proactively made, especially in those patients with spinal immobilization. Patients who are intoxicated may have altered mental status and are in a higher risk category. Seizure precautions are also recommended. Whenever possible, only trained personnel should mobilize an injured player and remove protective equipment. Frequent reassessments and monitoring of patients should be conducted during transport, with a focus on the GCS. A broad differential should be considered in patients sustaining traumatic head injury, and common causes of altered mental status such as hypoglycemia should not be overlooked (Table 11.2).

APPROACH/THE FOCUSED EXAMINATION

A focused history and physical examination direct the need for additional diagnostic testing. Findings may be subtle. The history focuses on the events surrounding the injury, including the presence of LOC and of pre- or post-traumatic amnesia; these findings establish that at a minimum there was a concussion, but the absence of these findings does not eliminate the diagnosis. Patients should be evaluated for common symptoms associated with concussion such as headache,
dizziness, fogginess, “feeling off” or imbalanced, blurred or double vision, or nausea/vomiting. These findings often occur rapidly after the injury, but may also develop hours to days after the injury (Table 11.3). The use of anticoagulant or antiplatelet medications should be assessed and may increase the likelihood of the patient having intracranial bleeding.

TABLE 11.2 Differential Diagnosis of Alert Patient Who Sustained a Head Injury and Presents with a Somatic Complaint

Complaint	Description
Cerebral contusion	Multiple microhemorrhages of brain tissue
Epidural hematoma	Extradural bleed, may see LOC followed by lucid interval, then decompensation with repeated LOC
Subdural hematoma	Bleed between dura mater and arachnoid mater, often tearing from bridging veins in subdural space
Intraparenchymal/intracerebral hematoma	Bleeding within brain parenchyma and may lead to edema and herniation
Intraventricular hematoma	Bleeding into ventricular system and CSF, typically associated with poor outcomes
Subarachnoid hemorrhage	May be associated with skull fracture or intracerebral contusion
Diffuse axonal injury	Shearing of axons diffusely, often causes comatose or vegetative state, may not be evident on CT and may require MRI for diagnosis
Metabolic abnormality	Consider hypoglycemia, dehydration, hyponatremia
Postictal state	May have period of amnesia, confusion
Skull fracture	Not necessarily associated with brain injury or AMS; assess for CSF leak
Post-traumatic headache	May be present without other concussion signs or symptoms; may take up to 7 days to develop after injury
Intoxication	May contribute to altered mental status and abnormal neurologic findings; may predispose patient to concussion; may be mixed alcohol and other substances
Post-traumatic stress disorder	Some overlap with concussion; often associated with intrusive images and memories of injury
Cranial nerve praxis	Double vision—often subtle, but may cause headache or sense of being off balance
Cervical strain	May cause headache
Cupulolithiasis	Can lead to vertigo and may lead to misdiagnosis of concussion
Medication overuse	Headache, somnolence, decreased concentration, and slowed reflexes
AMS, altered mental state; CSF, cerebrospinal fluid; CT, computed tomography; LOC, loss of consciousness; MRI, magnetic resonance imaging (eg, Headache).

The physical examination includes a primary and secondary survey. Examination of the skull, face, neck, and shoulders should be completed, looking for signs of traumatic injury such as hematoma, ecchymosis, lacerations, deformity, and/or tenderness. The cervical spine should be examined for tenderness with direct midline palpation or pain with range of motion from flexion/extension or turning to the sides.

The neurologic and cognitive examinations are at the core of the evaluation, and may reveal critically important, yet subtle, abnormalities, for example, a neuropraxia or a recall deficit. A best practice is to have a standardized evaluation template, for example, Sports Concussion Assessment
Tool-5 (SCAT5; see Tables 11.4 and 11.5). Specific standardized concussion examinations have not been validated in the ED; however, aspects of published sports or military tools (discussed subsequently) provide a framework to work from.

TABLE 11.3 Signs and Symptoms Associated with a Concussion

Signs	Symptoms	Examination Findings
Impact seizure	Headache	Amnesia
Fencing posturing	Nausea/vomiting	Cranial nerve abnormalities
LOC	Dizzy/imbalanced	Balance problems
Appears dazed/stunned	Blurred/double vision (CN)	Memory recall deficit
Gross motor instability	Irritable	Focal cranial nerve deficit
Confused or forgetful	Concentration/memory problems	Scalp hematoma
Slow to answer questions	Feels foggy/hazy/sluggish
	Amnesia
	Irritability/moody
	Sleep disturbance
	Loss of balance
	Photophobia/phonophobia
CN, cranial nerve; LOC, loss of consciousness.

The cranial nerve (CN) examination focuses on CN II, III, IV, and VI (of interest, retinal detachment is the most common injury in boxers, whereas subdural and intracranial bleeds are the most common cause of death); injury may lead to visual disturbances contributing to headaches and postural instability. Balance testing is a key component in the evaluation of the patient with an mTBI and a diagnostic criterion on sideline assessments. Although the evaluation of balance is formally assessed in the sports arena, there is no official technique validated for use in the ED. Tandem gait and coordination tests such as finger-to-nose have been shown to be a useful part of the examination.

Neurocognitive and psychological testing are used to measure changes in attention and higher level cognitive functioning, the hallmarks of mTBI. A brief, but appropriate, ED mental status examination should include orientation, immediate and delayed recall, concentration, attention span, mood, and speech and language skills. The testing of memory may be composed of both visual and verbal components. Reaction times and speed of processing may be assessed and may include problem-solving ability. Ideally, although not always practical, these results should be compared to baseline tests that are now standard during preseason assessments in sports.

Evaluation Tools

There are numerous assessment tools that have been developed to assess for a concussion, and should be considered when evaluating an injured person (Table 11.4). A limitation of many of these tools is the need to have an established baseline to compare performance to, which may not always be completed. Some of the tools include a physical examination component, and others known as neuropsychological tests are completely written or computerized. These tools may have a role in determining which patients with a head injury actually sustained a concussion.

SCAT5

The SCAT5⁷ is a standardized, commonly used sideline screening tool, used by medical professionals, that was designed for use in athletes aged 13 and older. It takes approximately 10 to 15 minutes to complete, and is often conducted with the assistance of an electronic device. Preseason baseline scores are generally established. If there is concern for a potential brain injury during practice or play, the athlete is retested on the sideline or locker room, and the scores are compared. The examination includes evaluating cognitive function, a detailed neurologic examination
including balance assessment, and symptom evaluation (Table 11.5). Currently, the SCAT is utilized by Fédération Internationale de Football Association (FIFA), National Football League (NFL), and some Olympic committees to help guide assessments, need for neuroimaging, and eligibility for return to play.

TABLE 11.4 Evaluation Tools for the Diagnosis of Concussions

Assessment Tool/Evaluation	Description
SCAT5: Sport Concussion Assessment Tool	See Table 11.5.
MACE²⁶: Military Acute Concussion Evaluation (MACE)	The military uses the MACE tool that includes a concussion screening history, a cognitive examination, a neurologic examination, and symptom screening. Baseline testing is often not available for comparison. The MACE first screens to confirm a patient had a head injury event and had either self-reported or witnessed alteration of consciousness (including being dazed, stunned, or seeing stars), loss of consciousness, or post-traumatic amnesia. If positive, a Standardized Assessment of Concussion (SAC) is then used to evaluate for deficits in four cognitive domains including orientation, immediate memory, concentration, and delayed recall. A score of 0-30 is then calculated. The MACE tool is ideally performed within the first 24 hr of the event and can be completed in a matter of minutes.
ImPACT: Immediate Post-concussion Assessment and Cognitive Testing	ImPACT is a computerized neurocognitive testing tool with objective scoring that can be compared to a patient’s baseline test results obtained preseason. It takes approximately 20-25 min, and is usually compared to baseline testing when available. There is no physical examination component to the ImPACT test, and it can be completed on a computer. It tests visual and verbal memory, attention span, reaction time, and visual and verbal problem-solving. ImPACT is used by many professional organizations including MLB, NHL, and many colleges and universities.
PCSI-2: Post-Concussion Symptom Inventory-2	PCSI-2 is a 5-min test that assesses physical, cognitive, emotional and sleep/fatigue symptoms to help manage treatment and guide a patient returning to activities.
K-D: King-Devick Test	This test takes 2 min and evaluates the speed of rapid number naming and captures impairment of eye movement, attention, and language that may correlate with identifying suboptimal brain function. It is a visual performance measure that captures saccadic eye movements, and is also commonly used in neurologic evaluations of nontraumatic patients.
ACE: Acute Concussion Evaluation	The ACE was released by the CDC as a free tool to standardize a symptom checklist to assess key elements including headache and visual symptoms, difficulty concentrating, fatigue, and irritability. There is no physical examination component. The tool also assesses risk factors for protracted recovery and helps guide a treatment and follow-up plan.
CDC, U.S. Centers for Disease Control and Prevention; MBL, Major League Basketball; NHL, National Hockey League.