The Natural History of Mild Traumatic Brain Injury

Grant L. Iverson, Noah D. Silverberg, and Rael T. Lange

INTRODUCTION

The natural history of mild traumatic brain injury (MTBI) is reasonably well understood. There is a substantial body of evidence suggesting that the symptoms and problems associated with this injury are time-limited and follow a predictable course for most people [1–6]. However, the literature on athletes with sport-related concussions and civilian trauma patients is largely distinct. Differences in patient characteristics, mechanisms of injury, study designs, and outcome measures make it difficult to integrate or even compare studies of athletes and civilian trauma patients.

RECOVERY IN ATHLETES WITH SPORT-RELATED CONCUSSION

Acute Clinical Presentation

Athletes report diverse physical, cognitive, and emotional symptoms in the acute phase. The most frequently endorsed symptoms in the initial days post injury are: headaches, fatigue, feeling slowed down, drowsiness, difficulty concentrating, feeling mentally foggy, and dizziness [7]. Impairment of balance and cognition is also common [8]. Younger athletes and females might have worse acute presentations [9].

Time Course for Recovery

Symptomatic recovery typically occurs within 2 weeks [5,6], but can take considerably longer for some athletes. The effect of concussion on balance and cognition diminish rapidly over the first 10 days following injury and are typically no longer detectable after 30 days following injury [9].

Factors Associated With Prolonged Recovery

Younger age (e.g., high school students versus adult professional athletes) and a history of prior concussion(s) are associated with slower symptom resolution [6].

RECOVERY OF CIVILIAN TRAUMA PATIENTS WHO PRESENT TO AN EMERGENCY DEPARTMENT WITH MTBI

Acute Clinical Presentation

Trauma patients with MTBI typically report a constellation of symptoms and perform poorly on neuropsychological tests in the initial days post injury (on average, about 0.4–1.0 standard deviations below a control group mean) [10–13]. The acute clinical presentation of civilian MTBI is often complicated by posttraumatic stress (in 15–25%) [14,15] and/or other bodily injuries (20–30%, not including soft tissue injuries) [16,17].

Time Course for Recovery

Symptoms generally improve over the first few weeks or months after MTBI. A minority of patients continue to report multiple symptoms at 1 year following injury [1]; estimates vary widely between studies, from less than 10% [18,19] to more than 50% [20,21]. When considering the low threshold for symptom endorsement in many studies, selection bias (recruiting only patients who present to the Emergency Department), and attrition (patients who recover well are more likely to drop out), we expect the true incidence of clinically significant chronic symptoms after MTBI to be on the lower end of that range. Whereas headache, nausea, and dizziness are common acutely, chronic symptoms are more likely to be emotional or cognitive in nature [22,23]. Patients with orthopaedic injuries below the neck report similar symptoms, in the absence of traumatic brain injury (TBI) [1], at similar [20,21] or lower [24,25] rates than trauma patients with MTBI, depending on the study. MTBI trauma patients, as a group, perform more poorly on cognitive testing up to the first month following the injury. Multiple meta-analyses have demonstrated that by 3 months post injury, trauma patients with MTBI perform similarly to those with orthopaedic injuries below the neck [26]. That is, they do not demonstrate cognitive impairment beyond that seen in a non-brain injured cohort of trauma patients. There is debate, however, as to whether a small subset of patients, not detected by meta-analytic methods that aggregate group data, have persistent cognitive impairment.

Factors Associated With Prolonged Recovery

A preinjury history of psychiatric problems is a robust predictor of chronic symptoms [27]. Acute psychological distress, in the initial days following injury, is associated with persistent symptoms [27]. Developing a psychiatric condition after MTBI can also complicate recovery. Women and older adults tend to take longer to recover [28]. There is not a clear and consistent association between measures of TBI severity, such as loss of consciousness and posttraumatic amnesia, and long-term outcome from MTBI. Patients with complicated MTBI (i.e., MTBI with trauma-related intracranial abnormalities noted on initial brain imaging) tend to perform more poorly on neuropsychological tests than patients with uncomplicated MTBI in the first 2 months following injury, but usually on a small number of tests rather than having globally depressed scores [29–33]. When differences occur between these two groups, the effect sizes of these differences tend to be medium. At 6 months post injury, the difference in neuropsychological test performance between complicated and uncomplicated MTBI patients seems to dissipate. Compensation-seeking is associated with prolonged recovery [34,35], but cause and effect in this relationship is not clear.

EARLY INTERVENTION

Clinicians may be able to facilitate recovery in people who have suffered a MTBI. Education and reassurance of a likely good outcome is the most researched type of early intervention. The benefits appear modest [36,37], but given the low cost of providing early education (e.g., in an information brochure), this intervention is probably worthwhile. Encouraging progressive return to activity as tolerated is probably more effective than advising prolonged rest [37]. There is insufficient evidence to recommend intensive multidisciplinary early intervention for the average patient with MTBI. However, targeted intervention for patients with risk factors for prolonged recovery is prudent.

RETURN TO SPORTS

Most professional football players who sustain a concussion miss no more than one game before returning to play [38]. High school and college athletes take about 1 week, on average, to return to competition [39], with more than 90% returning within 1 month [39]. Athletes with prior concussion(s) and adolescents (versus young adults) tend to take somewhat longer to recover symptomatically [6]. Age and concussion history may therefore be related to greater time to return to play after sport-related concussion. All of these studies are based on athlete samples, and may not apply to nonathletes returning to recreational sport and other activities.

RETURN TO WORK

Between 60% and 90% of patients return to work within 6 months of an MTBI in most studies [40–44]. Substantially lower rates have been reported in at least one cohort [45]. However, these participants were all admitted to the hospital and were therefore more severely injured. Lower education level, occupations involving low decision-making latitude, other bodily injuries, and severe acute symptoms appear to be associated with slower return to work [41,42]. Patients who were not injured at work tend to return to work faster than those with workplace injuries [46]. Access to compensation may at least partly explain this difference [47].

KEY POINTS

• The effects of MTBI typically improve over days (for sport-related concussion) or weeks (for trauma patients).

• Early education and advice to gradually resume preinjury activities can facilitate recovery.

• Protracted recovery is associated with a variety of biopsychosocial factors. To date, the best established predictors are age, sex, and in trauma patients, compensation-seeking and preinjury psychiatric problems.

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