Definition and Severity of Traumatic Brain Injury

Traumatic brain injury (TBI) is an alteration in brain function or other evidence of brain pathology caused by an external force.¹ TBI is a significant public health issue in the United States, with an estimated 1.7 million TBIs per year from 2002 to 2006.² Of those injured each year from 2002 to 2006, 1.37 million were treated and released from emergency departments, 275,000 were hospitalized, and 50,000 died from their injuries.² Additional TBIs not reflected in these numbers are treated in primary care settings and in Federal, military, and Veterans Affairs hospitals. The Department of Defense reported over 4,500 moderate to severe TBIs among all service members in 2010.³ Incidence is highest among children, adolescents, and young adults, but hospitalization and death occur most often among those age 75 and older.⁴ Major causes of TBIs include falls (35.2 percent), motor vehicle crashes (17.3 percent), struck by/against events (16.5 percent), assaults (10 percent), and other/unknown (21 percent); and, for military personnel or survivors of terrorist attacks, explosions/blasts. Blast incidents account for the majority of combat injuries, 60 percent of which result in TBI.^{4, 5}

TBIs are categorized as mild, moderate, or severe according to acute injury characteristics that suggest the extent of damage to the brain. Multiple measures are used to assess severity, including structural imaging findings; duration of loss of consciousness, altered consciousness and/or post-traumatic amnesia; the Glasgow Coma Scale (GCS) score; and the Abbreviated Injury Severity Scale score.⁶ The GCS is the most widely used scale to determine injury severity. However, GCS has significant limitations. For example, it is used at several timepoints, and studies of TBI do not always report which GCS measurement timepoint was used to assess severity. Additionally, GCS may not be the most accurate determinant of severity. Certain acute interventions such as intubation or specific medications can compromise the accuracy of the GCS score.⁷ Some experts have begun to support the use of other measures for severity based on research suggesting that loss of consciousness and posttraumatic amnesia may better predict functional status.⁷ Table 1 lists the various criteria and commonly used cut points for evaluating TBI severity:

Table 1

Criteria used to classify TBI severity.

• Structural imaging findings
• Duration of loss of consciousness
• Duration of altered consciousness
• Duration of post-traumatic amnesia
• Glasgow Coma Scale score

Sustained Impairments From Moderate to Severe TBI

Moderate to severe TBIs more often require intensive medical care, and 40 percent of those hospitalized with nonfatal moderate to severe TBI sustain impairments that lead to long-term disability.⁶ The Institute of Medicine (IOM) recently conducted a systematic review to identify long-term outcomes following TBI, which include seizures, growth hormone insufficiency, Alzheimer’s disease, endocrine dysfunction, Parkinsonism, adverse social functioning, neurocognitive deficits, diabetes insipidus, psychosis, and premature death.⁴ These outcomes have led some to encourage classifying TBI as the beginning of an ongoing, perhaps lifelong process, that affects multiple organ systems and may cause and accelerate disease.⁸ By one estimate, two percent of the U.S. population lives with TBI-related disabilities, presumably from moderate to severe TBI.⁹

Different injury types and severity levels are associated with specific impairments. For example, penetrating head injuries can result in cognitive decline related to injury location and amount of tissue lost;⁴ these injuries are associated with long-term unemployment and deficits similar to those observed in stroke patients.¹⁰ Closed head injuries, which are more common, result in diffuse brain damage that leads to impairments unique to the individual.¹⁰ Evidence suggests that long-lasting effects of moderate to severe TBI include cognitive deficits, psychiatric outcomes (depressive and aggressive behaviors, posttraumatic stress disorder in military populations, and psychoses), and social functioning (unemployment and diminished social relationships).¹¹

Specifically, sustained physical impairments may reduce endurance, cause headaches and seizures, and affect muscle tone, vision, hearing, smell, taste, and speech.¹² Sustained cognitive deficits may affect memory, attention, judgment, communication, planning, and spatial orientation.¹² Sustained affective/behavioral impairments include changes in mood, behavior, or personality that manifest as impulsiveness, passivity, agitation, loss of empathy, or emotional lability.¹⁰ The constellation of impairments following moderate to severe TBI can impede function and societal participation for months or years after injury.¹⁰

The degree of heterogeneity in number, types, and severity of impairments from moderate to severe TBI in adults must be noted. Many factors contribute to the wide range of impairments and impairment severity including injury type, extent and location of the brain tissue damaged, and patient factors such as age. Additionally, because TBI results from incidents such as motor vehicle crashes or blasts, TBI patients often have other injuries. Other injuries also occur frequently among certain population groups, such as falls in older individuals more likely to be living with preexisting conditions. Certain injuries occur under circumstances that initiate other disease processes, such as post-traumatic stress disorder. These factors and the interactions among them can affect recovery and response to rehabilitation, which creates challenges for intervention research on this topic.

Spontaneous Recovery

Spontaneous recovery refers to the restoration of function that naturally occurs after a brain injury. Controversy persists around the period and extent of spontaneous recovery after moderate to severe TBI. It is clear that some recovery of function occurs following traumatic brain injury, even with no rehabilitation.¹⁰ Additionally, certain psychiatric impairments may become more apparent several years postinjury.¹¹

Treatment for Moderate to Severe TBI

Patients with moderate to severe TBI are typically treated first in acute medical settings for a duration that depends on injury severity, impairment level, other injuries, patient age, and specific patient and healthcare system characteristics. Once the patient is medically stable, postacute care including rehabilitation may occur. This review includes any rehabilitation that occurs after acute medical treatment is complete; patients are medically stable, and able to participate in intensive rehabilitation programs. Those with multiple long-lasting impairments might participate in impairment-specific therapies, such as memory training. This report does not address such impairment-specific therapies. Those with multiple long-lasting impairments may enter multidisciplinary or comprehensive postacute rehabilitation programs.

Multidisciplinary Postacute Rehabilitation

Postacute rehabilitation programs address sustained impairments across physical, cognitive, and affective/behavioral domains and strive to improve functioning and participation. During the 1970s and ’80s, research emerged suggesting that domain-specific training may be insufficient to rehabilitate those with damage to the frontal lobe.¹³ Spurred by these findings, clinicians began to adopt holistic approaches to TBI rehabilitation, including vocational and neurobehavioral interventions that incorporate arranged work trials.¹³ While a standard definition for these comprehensive programs does not exist, the current preferred approach is multidisciplinary, with treatments (including for comorbidities) integrated across disciplines or impairment domains.

A recent systematic review of multidisciplinary rehabilitation post brain injury defines “multidisciplinary” as more than one discipline working in coordination.¹⁴ In the literature, these programs are described by a variety of terms including multidisciplinary, interdisciplinary, comprehensive, holistic, neurobehavioral, neurorehabilitation, and integrated. Multidisciplinary teams often include physiatrists; neurologists; neuropsychologists; clinical psychologists; physical and occupational therapists; speech language pathologists; recreational therapists; social workers; rehabilitation nurses; and technicians. Multidisciplinary programs differ in their settings, components, emphases, and degree of structure. Furthermore, an individual’s sustained impairments may largely determine the composition, intensity, and duration of rehabilitation. While there appears to be a general understanding that comprehensive programs are comprised of many different professionals working as a team, it is difficult to find program descriptions that specify percentages or doses of the various available therapies. Instead, programs are often variable and seen as a function of specific patients’ presumed needs.

Multidisciplinary rehabilitation programs for brain injury lack a clear and consistent taxonomy.¹⁴ Malec and Basford describe four types of programs: neurobehavioral, residential community reintegration, comprehensive (holistic) day treatment, and outpatient community re-entry. Neurobehavioral programs provide behavioral interventions for patients with significant behavioral disturbances.¹⁵ Residential community reintegration programs treat those who either lack access to outpatient services, or have impairments that preclude it. These programs integrate cognitive, emotional, behavioral, physical, and vocational rehabilitation. Malec defines comprehensive (holistic) day treatment programs as those that offer integrated multimodal rehabilitation emphasizing self-awareness.¹⁵ Outpatient community reintegration programs offer circumscribed rehabilitation treatments and vocational and social reintegration.¹⁵ Depending on impairment type and access, individuals may or may not participate in postacute rehabilitation, or may cycle through several programs. Adults with TBI who are not enrolled in a specific program may instead participate in community-based rehabilitation services.¹⁵

Outcomes of Postacute Rehabilitation

Clinicians and researchers have used various outcomes measures to assess the effectiveness of postacute rehabilitation. Patient-centered outcomes are those valued by patients.¹⁶ Patient-centered outcomes for rehabilitation of moderate to severe TBI impairments likely reflect the participation domain of the International Classification of Functioning, Disability, and Health (ICF) framework, created to classify and assess function and disability associated with health conditions.¹⁷ This multidimensional framework (Figure 1): (1) rests on a positive description of human functioning rather than emphasizing the negative consequences of disease; (2) incorporates several levels of influence; and (3) attempts to explicitly acknowledge the dynamic nature of disablement, which fluctuates based on a number of contributing factors across stages of recovery. The ICF emphasizes the complex way in which condition and contextual factors may modify outcomes including participation. One study examined this complexity by conducting pathway analysis of a sample of severe TBI patients to explore the causal, predictive relationships that affect outcomes after TBI.¹⁸ Their modeling suggested that cognitive status and premorbid status were important predictors of outcomes, and that these factors may be more important than injury severity for longer term outcomes such as participation. Nonetheless, participation remains a widely recognized goal of rehabilitation, despite many factors that may influence this outcome.^19–21

Figure 1

The International Classification of Function, Disability, and Health (ICF).

Ultimately, survivors of TBI and their families hope for reintegration into previous roles and activities. Therefore, the goal of TBI rehabilitation is to help patients resume meaningful participation in their homes and social environments, regardless of whether specific impairments can be eliminated.²⁰ For many brain injury survivors, a final goal of community integration may be to return to work, school, or training, all of which are often classified as “productivity” outcomes. Additionally, researchers and practitioners agree that “community integration” outcomes, related to the resumption of societal roles, are important indicators of effectiveness for TBI rehabilitation.²⁰

Several scales are available for assessing community reintegration in the brain injury population, such as the Mayo-Portland Adaptability Index (MPAI)²² and the Community Integration Questionnaire (CIQ)²³. However, interpreting whether scale score changes are meaningful presents a challenge. Research using scale scores as outcomes is complicated because we don’t know exactly what statistically significant changes in scale scores mean clinically to patients. It is imperative to identify the level of change in a particular scale score that equates to a meaningful improvement for patients and their families. Interpreting effectiveness and comparative effectiveness hinges on adequately understanding this meaningful level of change, often called the minimal important difference or the minimum clinically important difference (MCID). MCID has been defined as the smallest difference in an outcome scale that can be perceived by patients as being beneficial.²⁴ However, the identification and use of MCID raises challenges as well, such as the applicability of the context and methodology in which MCID is established.²⁵

Key Question 1

How have studies characterized multidisciplinary postacute rehabilitation for TBI in adults?

Key Question 2

What is the effectiveness and comparative effectiveness of multidisciplinary postacute rehabilitation for TBI?

1. Do effectiveness and comparative effectiveness vary by rehabilitation timing, setting, intensity, duration, or composition?
2. Do effectiveness and comparative effectiveness vary by injury characteristics?
3. Do effectiveness and comparative effectiveness vary by patient characteristics, preinjury or postinjury?

Key Question 3

What evidence exists to establish a minimum clinically important difference in community reintegration as measured by the Mayo-Portland Adaptability Inventory (MPAI-4) for postacute rehabilitation for TBI in adults?

Key Question 4

Are improvements in outcomes achieved via multidisciplinary postacute rehabilitation for TBI sustained over time?

Key Question 5

What adverse effects are associated with multidisciplinary postacute rehabilitation for TBI?

We address these Key Questions in the context of our analytical framework (Figure 2). This framework greatly simplifies the complex process navigated by those with sustained impairments from moderate to severe TBI. For instance, spontaneous recovery may occur simultaneously with rehabilitation, which complicates efforts to distinguish natural improvements from those due to treatment.¹⁰ Furthermore, rate of progress and level of effectiveness with rehabilitation can be affected by characteristics of patients and families, injuries and comorbidities, and interventions, and by relationships between these characteristics. Multiplicity of outcomes presents another challenge. Often, progress in response to particular therapies is monitored with measures that evaluate isolated impairments (e.g., memory, attention, or aggressive behavior). Other intermediate measures are used to assess the progress of individuals in rehabilitation settings. Finally, patient-centered outcomes evaluate the success of rehabilitation in returning TBI survivors to roles in the community.

Figure 2

Analytic framework.