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.
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
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